From 490cc7d03c21871eef5949ba77a18b0c7ef70ef5 Mon Sep 17 00:00:00 2001 From: Willem de Bruijn Date: Tue, 12 Aug 2014 15:08:12 -0400 Subject: net-timestamp: fix missing tcp fragmentation cases Bytestream timestamps are correlated with a single byte in the skbuff, recorded in skb_shinfo(skb)->tskey. When fragmenting skbuffs, ensure that the tskey is set for the fragment in which the tskey falls (seqno <= tskey < end_seqno). The original implementation did not address fragmentation in tcp_fragment or tso_fragment. Add code to inspect the sequence numbers and move both tskey and the relevant tx_flags if necessary. Reported-by: Eric Dumazet Signed-off-by: Willem de Bruijn Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'net/ipv4/tcp_output.c') diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 8fcfc91964e..ef4a051de01 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1069,6 +1069,21 @@ static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int de tcp_verify_left_out(tp); } +static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2) +{ + struct skb_shared_info *shinfo = skb_shinfo(skb); + + if (unlikely(shinfo->tx_flags & SKBTX_ANY_TSTAMP) && + !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) { + struct skb_shared_info *shinfo2 = skb_shinfo(skb2); + u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP; + + shinfo->tx_flags &= ~tsflags; + shinfo2->tx_flags |= tsflags; + swap(shinfo->tskey, shinfo2->tskey); + } +} + /* Function to create two new TCP segments. Shrinks the given segment * to the specified size and appends a new segment with the rest of the * packet to the list. This won't be called frequently, I hope. @@ -1136,6 +1151,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, */ TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when; buff->tstamp = skb->tstamp; + tcp_fragment_tstamp(skb, buff); old_factor = tcp_skb_pcount(skb); @@ -1652,6 +1668,7 @@ static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL; skb_split(skb, buff, len); + tcp_fragment_tstamp(skb, buff); /* Fix up tso_factor for both original and new SKB. */ tcp_set_skb_tso_segs(sk, skb, mss_now); -- cgit v1.2.3-70-g09d2 From 9d186cac7ffb1831e9f34cb4a3a8b22abb9dd9d4 Mon Sep 17 00:00:00 2001 From: Andrey Vagin Date: Wed, 13 Aug 2014 16:03:10 +0400 Subject: tcp: don't use timestamp from repaired skb-s to calculate RTT (v2) We don't know right timestamp for repaired skb-s. Wrong RTT estimations isn't good, because some congestion modules heavily depends on it. This patch adds the TCPCB_REPAIRED flag, which is included in TCPCB_RETRANS. Thanks to Eric for the advice how to fix this issue. This patch fixes the warning: [ 879.562947] WARNING: CPU: 0 PID: 2825 at net/ipv4/tcp_input.c:3078 tcp_ack+0x11f5/0x1380() [ 879.567253] CPU: 0 PID: 2825 Comm: socket-tcpbuf-l Not tainted 3.16.0-next-20140811 #1 [ 879.567829] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 879.568177] 0000000000000000 00000000c532680c ffff880039643d00 ffffffff817aa2d2 [ 879.568776] 0000000000000000 ffff880039643d38 ffffffff8109afbd ffff880039d6ba80 [ 879.569386] ffff88003a449800 000000002983d6bd 0000000000000000 000000002983d6bc [ 879.569982] Call Trace: [ 879.570264] [] dump_stack+0x4d/0x66 [ 879.570599] [] warn_slowpath_common+0x7d/0xa0 [ 879.570935] [] warn_slowpath_null+0x1a/0x20 [ 879.571292] [] tcp_ack+0x11f5/0x1380 [ 879.571614] [] tcp_rcv_established+0x1ed/0x710 [ 879.571958] [] tcp_v4_do_rcv+0x10a/0x370 [ 879.572315] [] release_sock+0x89/0x1d0 [ 879.572642] [] do_tcp_setsockopt.isra.36+0x120/0x860 [ 879.573000] [] ? rcu_read_lock_held+0x6e/0x80 [ 879.573352] [] tcp_setsockopt+0x32/0x40 [ 879.573678] [] sock_common_setsockopt+0x14/0x20 [ 879.574031] [] SyS_setsockopt+0x80/0xf0 [ 879.574393] [] system_call_fastpath+0x16/0x1b [ 879.574730] ---[ end trace a17cbc38eb8c5c00 ]--- v2: moving setting of skb->when for repaired skb-s in tcp_write_xmit, where it's set for other skb-s. Fixes: 431a91242d8d ("tcp: timestamp SYN+DATA messages") Fixes: 740b0f1841f6 ("tcp: switch rtt estimations to usec resolution") Cc: Eric Dumazet Cc: Pavel Emelyanov Cc: "David S. Miller" Signed-off-by: Andrey Vagin Signed-off-by: David S. Miller --- include/net/tcp.h | 4 +++- net/ipv4/tcp.c | 14 +++++++------- net/ipv4/tcp_output.c | 5 ++++- 3 files changed, 14 insertions(+), 9 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/include/net/tcp.h b/include/net/tcp.h index dafa1cbc149..36f55254573 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -705,8 +705,10 @@ struct tcp_skb_cb { #define TCPCB_SACKED_RETRANS 0x02 /* SKB retransmitted */ #define TCPCB_LOST 0x04 /* SKB is lost */ #define TCPCB_TAGBITS 0x07 /* All tag bits */ +#define TCPCB_REPAIRED 0x10 /* SKB repaired (no skb_mstamp) */ #define TCPCB_EVER_RETRANS 0x80 /* Ever retransmitted frame */ -#define TCPCB_RETRANS (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS) +#define TCPCB_RETRANS (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \ + TCPCB_REPAIRED) __u8 ip_dsfield; /* IPv4 tos or IPv6 dsfield */ /* 1 byte hole */ diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 181b70ebd96..541f26a67ba 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1187,13 +1187,6 @@ new_segment: if (!skb) goto wait_for_memory; - /* - * All packets are restored as if they have - * already been sent. - */ - if (tp->repair) - TCP_SKB_CB(skb)->when = tcp_time_stamp; - /* * Check whether we can use HW checksum. */ @@ -1203,6 +1196,13 @@ new_segment: skb_entail(sk, skb); copy = size_goal; max = size_goal; + + /* All packets are restored as if they have + * already been sent. skb_mstamp isn't set to + * avoid wrong rtt estimation. + */ + if (tp->repair) + TCP_SKB_CB(skb)->sacked |= TCPCB_REPAIRED; } /* Try to append data to the end of skb. */ diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index ef4a051de01..ff3f0f75cc6 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1934,8 +1934,11 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, tso_segs = tcp_init_tso_segs(sk, skb, mss_now); BUG_ON(!tso_segs); - if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) + if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) { + /* "when" is used as a start point for the retransmit timer */ + TCP_SKB_CB(skb)->when = tcp_time_stamp; goto repair; /* Skip network transmission */ + } cwnd_quota = tcp_cwnd_test(tp, skb); if (!cwnd_quota) { -- cgit v1.2.3-70-g09d2 From 4fab9071950c2021d846e18351e0f46a1cffd67b Mon Sep 17 00:00:00 2001 From: Neal Cardwell Date: Thu, 14 Aug 2014 12:40:05 -0400 Subject: tcp: fix tcp_release_cb() to dispatch via address family for mtu_reduced() Make sure we use the correct address-family-specific function for handling MTU reductions from within tcp_release_cb(). Previously AF_INET6 sockets were incorrectly always using the IPv6 code path when sometimes they were handling IPv4 traffic and thus had an IPv4 dst. Signed-off-by: Neal Cardwell Signed-off-by: Eric Dumazet Diagnosed-by: Willem de Bruijn Fixes: 563d34d057862 ("tcp: dont drop MTU reduction indications") Reviewed-by: Hannes Frederic Sowa Signed-off-by: David S. Miller --- include/net/inet_connection_sock.h | 1 + include/net/sock.h | 1 - include/net/tcp.h | 1 + net/ipv4/tcp_ipv4.c | 5 +++-- net/ipv4/tcp_output.c | 2 +- net/ipv6/tcp_ipv6.c | 3 ++- 6 files changed, 8 insertions(+), 5 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h index 7a431388756..5fbe6568c3c 100644 --- a/include/net/inet_connection_sock.h +++ b/include/net/inet_connection_sock.h @@ -62,6 +62,7 @@ struct inet_connection_sock_af_ops { void (*addr2sockaddr)(struct sock *sk, struct sockaddr *); int (*bind_conflict)(const struct sock *sk, const struct inet_bind_bucket *tb, bool relax); + void (*mtu_reduced)(struct sock *sk); }; /** inet_connection_sock - INET connection oriented sock diff --git a/include/net/sock.h b/include/net/sock.h index 38805fa02e4..7f2ab72f321 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -987,7 +987,6 @@ struct proto { struct sk_buff *skb); void (*release_cb)(struct sock *sk); - void (*mtu_reduced)(struct sock *sk); /* Keeping track of sk's, looking them up, and port selection methods. */ void (*hash)(struct sock *sk); diff --git a/include/net/tcp.h b/include/net/tcp.h index 36f55254573..e337e05035b 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -448,6 +448,7 @@ const u8 *tcp_parse_md5sig_option(const struct tcphdr *th); */ void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb); +void tcp_v4_mtu_reduced(struct sock *sk); int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb); struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req, diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index dceff5fe8e6..cd17f009aed 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -271,7 +271,7 @@ EXPORT_SYMBOL(tcp_v4_connect); * It can be called through tcp_release_cb() if socket was owned by user * at the time tcp_v4_err() was called to handle ICMP message. */ -static void tcp_v4_mtu_reduced(struct sock *sk) +void tcp_v4_mtu_reduced(struct sock *sk) { struct dst_entry *dst; struct inet_sock *inet = inet_sk(sk); @@ -302,6 +302,7 @@ static void tcp_v4_mtu_reduced(struct sock *sk) tcp_simple_retransmit(sk); } /* else let the usual retransmit timer handle it */ } +EXPORT_SYMBOL(tcp_v4_mtu_reduced); static void do_redirect(struct sk_buff *skb, struct sock *sk) { @@ -1787,6 +1788,7 @@ const struct inet_connection_sock_af_ops ipv4_specific = { .compat_setsockopt = compat_ip_setsockopt, .compat_getsockopt = compat_ip_getsockopt, #endif + .mtu_reduced = tcp_v4_mtu_reduced, }; EXPORT_SYMBOL(ipv4_specific); @@ -2406,7 +2408,6 @@ struct proto tcp_prot = { .sendpage = tcp_sendpage, .backlog_rcv = tcp_v4_do_rcv, .release_cb = tcp_release_cb, - .mtu_reduced = tcp_v4_mtu_reduced, .hash = inet_hash, .unhash = inet_unhash, .get_port = inet_csk_get_port, diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index ff3f0f75cc6..5a7c41fbc6d 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -800,7 +800,7 @@ void tcp_release_cb(struct sock *sk) __sock_put(sk); } if (flags & (1UL << TCP_MTU_REDUCED_DEFERRED)) { - sk->sk_prot->mtu_reduced(sk); + inet_csk(sk)->icsk_af_ops->mtu_reduced(sk); __sock_put(sk); } } diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index f2ce9550239..29964c3d363 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1595,6 +1595,7 @@ static const struct inet_connection_sock_af_ops ipv6_specific = { .compat_setsockopt = compat_ipv6_setsockopt, .compat_getsockopt = compat_ipv6_getsockopt, #endif + .mtu_reduced = tcp_v6_mtu_reduced, }; #ifdef CONFIG_TCP_MD5SIG @@ -1625,6 +1626,7 @@ static const struct inet_connection_sock_af_ops ipv6_mapped = { .compat_setsockopt = compat_ipv6_setsockopt, .compat_getsockopt = compat_ipv6_getsockopt, #endif + .mtu_reduced = tcp_v4_mtu_reduced, }; #ifdef CONFIG_TCP_MD5SIG @@ -1864,7 +1866,6 @@ struct proto tcpv6_prot = { .sendpage = tcp_sendpage, .backlog_rcv = tcp_v6_do_rcv, .release_cb = tcp_release_cb, - .mtu_reduced = tcp_v6_mtu_reduced, .hash = tcp_v6_hash, .unhash = inet_unhash, .get_port = inet_csk_get_port, -- cgit v1.2.3-70-g09d2 From 903ceff7ca7b4d80c083a80ee5163b74e9fa359f Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Sun, 17 Aug 2014 12:30:35 -0500 Subject: net: Replace get_cpu_var through this_cpu_ptr Replace uses of get_cpu_var for address calculation through this_cpu_ptr. Cc: netdev@vger.kernel.org Cc: Eric Dumazet Acked-by: David S. Miller Signed-off-by: Christoph Lameter Signed-off-by: Tejun Heo --- include/net/netfilter/nf_conntrack.h | 2 +- include/net/snmp.h | 6 +++--- net/core/dev.c | 14 +++++++------- net/core/drop_monitor.c | 2 +- net/core/skbuff.c | 2 +- net/ipv4/route.c | 4 ++-- net/ipv4/syncookies.c | 2 +- net/ipv4/tcp.c | 2 +- net/ipv4/tcp_output.c | 2 +- net/ipv6/syncookies.c | 2 +- net/rds/ib_rdma.c | 2 +- 11 files changed, 20 insertions(+), 20 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h index 37252f71a38..c8a7db605e0 100644 --- a/include/net/netfilter/nf_conntrack.h +++ b/include/net/netfilter/nf_conntrack.h @@ -242,7 +242,7 @@ extern s32 (*nf_ct_nat_offset)(const struct nf_conn *ct, DECLARE_PER_CPU(struct nf_conn, nf_conntrack_untracked); static inline struct nf_conn *nf_ct_untracked_get(void) { - return &__raw_get_cpu_var(nf_conntrack_untracked); + return raw_cpu_ptr(&nf_conntrack_untracked); } void nf_ct_untracked_status_or(unsigned long bits); diff --git a/include/net/snmp.h b/include/net/snmp.h index f1f27fdbb0d..e154133877a 100644 --- a/include/net/snmp.h +++ b/include/net/snmp.h @@ -168,7 +168,7 @@ struct linux_xfrm_mib { #define SNMP_ADD_STATS64_BH(mib, field, addend) \ do { \ - __typeof__(*mib) *ptr = __this_cpu_ptr(mib); \ + __typeof__(*mib) *ptr = raw_cpu_ptr(mib); \ u64_stats_update_begin(&ptr->syncp); \ ptr->mibs[field] += addend; \ u64_stats_update_end(&ptr->syncp); \ @@ -189,8 +189,8 @@ struct linux_xfrm_mib { #define SNMP_INC_STATS64(mib, field) SNMP_ADD_STATS64(mib, field, 1) #define SNMP_UPD_PO_STATS64_BH(mib, basefield, addend) \ do { \ - __typeof__(*mib) *ptr; \ - ptr = __this_cpu_ptr(mib); \ + __typeof__(*mib) *ptr; \ + ptr = raw_cpu_ptr((mib)); \ u64_stats_update_begin(&ptr->syncp); \ ptr->mibs[basefield##PKTS]++; \ ptr->mibs[basefield##OCTETS] += addend; \ diff --git a/net/core/dev.c b/net/core/dev.c index b65a5051361..9ef13ff354f 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2153,7 +2153,7 @@ static inline void __netif_reschedule(struct Qdisc *q) unsigned long flags; local_irq_save(flags); - sd = &__get_cpu_var(softnet_data); + sd = this_cpu_ptr(&softnet_data); q->next_sched = NULL; *sd->output_queue_tailp = q; sd->output_queue_tailp = &q->next_sched; @@ -3195,7 +3195,7 @@ static void rps_trigger_softirq(void *data) static int rps_ipi_queued(struct softnet_data *sd) { #ifdef CONFIG_RPS - struct softnet_data *mysd = &__get_cpu_var(softnet_data); + struct softnet_data *mysd = this_cpu_ptr(&softnet_data); if (sd != mysd) { sd->rps_ipi_next = mysd->rps_ipi_list; @@ -3222,7 +3222,7 @@ static bool skb_flow_limit(struct sk_buff *skb, unsigned int qlen) if (qlen < (netdev_max_backlog >> 1)) return false; - sd = &__get_cpu_var(softnet_data); + sd = this_cpu_ptr(&softnet_data); rcu_read_lock(); fl = rcu_dereference(sd->flow_limit); @@ -3369,7 +3369,7 @@ EXPORT_SYMBOL(netif_rx_ni); static void net_tx_action(struct softirq_action *h) { - struct softnet_data *sd = &__get_cpu_var(softnet_data); + struct softnet_data *sd = this_cpu_ptr(&softnet_data); if (sd->completion_queue) { struct sk_buff *clist; @@ -3794,7 +3794,7 @@ EXPORT_SYMBOL(netif_receive_skb); static void flush_backlog(void *arg) { struct net_device *dev = arg; - struct softnet_data *sd = &__get_cpu_var(softnet_data); + struct softnet_data *sd = this_cpu_ptr(&softnet_data); struct sk_buff *skb, *tmp; rps_lock(sd); @@ -4301,7 +4301,7 @@ void __napi_schedule(struct napi_struct *n) unsigned long flags; local_irq_save(flags); - ____napi_schedule(&__get_cpu_var(softnet_data), n); + ____napi_schedule(this_cpu_ptr(&softnet_data), n); local_irq_restore(flags); } EXPORT_SYMBOL(__napi_schedule); @@ -4422,7 +4422,7 @@ EXPORT_SYMBOL(netif_napi_del); static void net_rx_action(struct softirq_action *h) { - struct softnet_data *sd = &__get_cpu_var(softnet_data); + struct softnet_data *sd = this_cpu_ptr(&softnet_data); unsigned long time_limit = jiffies + 2; int budget = netdev_budget; void *have; diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c index 50f9a9db579..252e155c837 100644 --- a/net/core/drop_monitor.c +++ b/net/core/drop_monitor.c @@ -146,7 +146,7 @@ static void trace_drop_common(struct sk_buff *skb, void *location) unsigned long flags; local_irq_save(flags); - data = &__get_cpu_var(dm_cpu_data); + data = this_cpu_ptr(&dm_cpu_data); spin_lock(&data->lock); dskb = data->skb; diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 163b673f9e6..adfc7ee1acf 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -345,7 +345,7 @@ static void *__netdev_alloc_frag(unsigned int fragsz, gfp_t gfp_mask) unsigned long flags; local_irq_save(flags); - nc = &__get_cpu_var(netdev_alloc_cache); + nc = this_cpu_ptr(&netdev_alloc_cache); if (unlikely(!nc->frag.page)) { refill: for (order = NETDEV_FRAG_PAGE_MAX_ORDER; ;) { diff --git a/net/ipv4/route.c b/net/ipv4/route.c index eaa4b000c7b..7d6f4e02184 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1311,7 +1311,7 @@ static bool rt_cache_route(struct fib_nh *nh, struct rtable *rt) if (rt_is_input_route(rt)) { p = (struct rtable **)&nh->nh_rth_input; } else { - p = (struct rtable **)__this_cpu_ptr(nh->nh_pcpu_rth_output); + p = (struct rtable **)raw_cpu_ptr(nh->nh_pcpu_rth_output); } orig = *p; @@ -1939,7 +1939,7 @@ static struct rtable *__mkroute_output(const struct fib_result *res, do_cache = false; goto add; } - prth = __this_cpu_ptr(nh->nh_pcpu_rth_output); + prth = raw_cpu_ptr(nh->nh_pcpu_rth_output); } rth = rcu_dereference(*prth); if (rt_cache_valid(rth)) { diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c index c0c75688896..f83391bfdd7 100644 --- a/net/ipv4/syncookies.c +++ b/net/ipv4/syncookies.c @@ -40,7 +40,7 @@ static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport, net_get_random_once(syncookie_secret, sizeof(syncookie_secret)); - tmp = __get_cpu_var(ipv4_cookie_scratch); + tmp = this_cpu_ptr(ipv4_cookie_scratch); memcpy(tmp + 4, syncookie_secret[c], sizeof(syncookie_secret[c])); tmp[0] = (__force u32)saddr; tmp[1] = (__force u32)daddr; diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 541f26a67ba..b2cab7770a1 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3058,7 +3058,7 @@ struct tcp_md5sig_pool *tcp_get_md5sig_pool(void) local_bh_disable(); p = ACCESS_ONCE(tcp_md5sig_pool); if (p) - return __this_cpu_ptr(p); + return raw_cpu_ptr(p); local_bh_enable(); return NULL; diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 5a7c41fbc6d..d145f7ef78f 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -842,7 +842,7 @@ void tcp_wfree(struct sk_buff *skb) /* queue this socket to tasklet queue */ local_irq_save(flags); - tsq = &__get_cpu_var(tsq_tasklet); + tsq = this_cpu_ptr(&tsq_tasklet); list_add(&tp->tsq_node, &tsq->head); tasklet_schedule(&tsq->tasklet); local_irq_restore(flags); diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c index 83cea1d3946..637de5b8758 100644 --- a/net/ipv6/syncookies.c +++ b/net/ipv6/syncookies.c @@ -67,7 +67,7 @@ static u32 cookie_hash(const struct in6_addr *saddr, const struct in6_addr *dadd net_get_random_once(syncookie6_secret, sizeof(syncookie6_secret)); - tmp = __get_cpu_var(ipv6_cookie_scratch); + tmp = this_cpu_ptr(ipv6_cookie_scratch); /* * we have 320 bits of information to hash, copy in the remaining diff --git a/net/rds/ib_rdma.c b/net/rds/ib_rdma.c index e8fdb172adb..273b8bff6ba 100644 --- a/net/rds/ib_rdma.c +++ b/net/rds/ib_rdma.c @@ -267,7 +267,7 @@ static inline struct rds_ib_mr *rds_ib_reuse_fmr(struct rds_ib_mr_pool *pool) unsigned long *flag; preempt_disable(); - flag = &__get_cpu_var(clean_list_grace); + flag = this_cpu_ptr(&clean_list_grace); set_bit(CLEAN_LIST_BUSY_BIT, flag); ret = llist_del_first(&pool->clean_list); if (ret) -- cgit v1.2.3-70-g09d2 From 7faee5c0d514162853a343d93e4a0b6bb8bfec21 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 5 Sep 2014 15:33:33 -0700 Subject: tcp: remove TCP_SKB_CB(skb)->when After commit 740b0f1841f6 ("tcp: switch rtt estimations to usec resolution"), we no longer need to maintain timestamps in two different fields. TCP_SKB_CB(skb)->when can be removed, as same information sits in skb_mstamp.stamp_jiffies Signed-off-by: Eric Dumazet Acked-by: Yuchung Cheng Signed-off-by: David S. Miller --- include/net/tcp.h | 13 +++++++------ net/ipv4/tcp_input.c | 3 ++- net/ipv4/tcp_ipv4.c | 5 +++-- net/ipv4/tcp_output.c | 39 ++++++++++++++++----------------------- net/ipv4/tcp_timer.c | 7 +++---- 5 files changed, 31 insertions(+), 36 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/include/net/tcp.h b/include/net/tcp.h index 0cd7d2c65dc..a4201ef216e 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -672,6 +672,12 @@ void tcp_send_window_probe(struct sock *sk); */ #define tcp_time_stamp ((__u32)(jiffies)) +static inline u32 tcp_skb_timestamp(const struct sk_buff *skb) +{ + return skb->skb_mstamp.stamp_jiffies; +} + + #define tcp_flag_byte(th) (((u_int8_t *)th)[13]) #define TCPHDR_FIN 0x01 @@ -698,12 +704,7 @@ struct tcp_skb_cb { } header; /* For incoming frames */ __u32 seq; /* Starting sequence number */ __u32 end_seq; /* SEQ + FIN + SYN + datalen */ - union { - /* used in output path */ - __u32 when; /* used to compute rtt's */ - /* used in input path */ - __u32 tcp_tw_isn; /* isn chosen by tcp_timewait_state_process() */ - }; + __u32 tcp_tw_isn; /* isn chosen by tcp_timewait_state_process() */ __u8 tcp_flags; /* TCP header flags. (tcp[13]) */ __u8 sacked; /* State flags for SACK/FACK. */ diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 9c8b9f1dcf6..f97003ad0af 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2967,7 +2967,8 @@ void tcp_rearm_rto(struct sock *sk) if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) { struct sk_buff *skb = tcp_write_queue_head(sk); - const u32 rto_time_stamp = TCP_SKB_CB(skb)->when + rto; + const u32 rto_time_stamp = + tcp_skb_timestamp(skb) + rto; s32 delta = (s32)(rto_time_stamp - tcp_time_stamp); /* delta may not be positive if the socket is locked * when the retrans timer fires and is rescheduled. diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 02e6cd29ebf..3f9bc3f0bba 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -437,8 +437,9 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info) skb = tcp_write_queue_head(sk); BUG_ON(!skb); - remaining = icsk->icsk_rto - min(icsk->icsk_rto, - tcp_time_stamp - TCP_SKB_CB(skb)->when); + remaining = icsk->icsk_rto - + min(icsk->icsk_rto, + tcp_time_stamp - tcp_skb_timestamp(skb)); if (remaining) { inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 5a7c41fbc6d..3b22dcb7bb5 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -550,7 +550,7 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, if (likely(sysctl_tcp_timestamps && *md5 == NULL)) { opts->options |= OPTION_TS; - opts->tsval = TCP_SKB_CB(skb)->when + tp->tsoffset; + opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset; opts->tsecr = tp->rx_opt.ts_recent; remaining -= TCPOLEN_TSTAMP_ALIGNED; } @@ -618,7 +618,7 @@ static unsigned int tcp_synack_options(struct sock *sk, } if (likely(ireq->tstamp_ok)) { opts->options |= OPTION_TS; - opts->tsval = TCP_SKB_CB(skb)->when; + opts->tsval = tcp_skb_timestamp(skb); opts->tsecr = req->ts_recent; remaining -= TCPOLEN_TSTAMP_ALIGNED; } @@ -647,7 +647,6 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb struct tcp_out_options *opts, struct tcp_md5sig_key **md5) { - struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL; struct tcp_sock *tp = tcp_sk(sk); unsigned int size = 0; unsigned int eff_sacks; @@ -666,7 +665,7 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb if (likely(tp->rx_opt.tstamp_ok)) { opts->options |= OPTION_TS; - opts->tsval = tcb ? tcb->when + tp->tsoffset : 0; + opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0; opts->tsecr = tp->rx_opt.ts_recent; size += TCPOLEN_TSTAMP_ALIGNED; } @@ -886,8 +885,6 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, skb = skb_clone(skb, gfp_mask); if (unlikely(!skb)) return -ENOBUFS; - /* Our usage of tstamp should remain private */ - skb->tstamp.tv64 = 0; } inet = inet_sk(sk); @@ -975,7 +972,10 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS, tcp_skb_pcount(skb)); + /* Our usage of tstamp should remain private */ + skb->tstamp.tv64 = 0; err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl); + if (likely(err <= 0)) return err; @@ -1149,7 +1149,6 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, /* Looks stupid, but our code really uses when of * skbs, which it never sent before. --ANK */ - TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when; buff->tstamp = skb->tstamp; tcp_fragment_tstamp(skb, buff); @@ -1874,8 +1873,8 @@ static int tcp_mtu_probe(struct sock *sk) tcp_init_tso_segs(sk, nskb, nskb->len); /* We're ready to send. If this fails, the probe will - * be resegmented into mss-sized pieces by tcp_write_xmit(). */ - TCP_SKB_CB(nskb)->when = tcp_time_stamp; + * be resegmented into mss-sized pieces by tcp_write_xmit(). + */ if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) { /* Decrement cwnd here because we are sending * effectively two packets. */ @@ -1935,8 +1934,8 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, BUG_ON(!tso_segs); if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) { - /* "when" is used as a start point for the retransmit timer */ - TCP_SKB_CB(skb)->when = tcp_time_stamp; + /* "skb_mstamp" is used as a start point for the retransmit timer */ + skb_mstamp_get(&skb->skb_mstamp); goto repair; /* Skip network transmission */ } @@ -2000,8 +1999,6 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, unlikely(tso_fragment(sk, skb, limit, mss_now, gfp))) break; - TCP_SKB_CB(skb)->when = tcp_time_stamp; - if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp))) break; @@ -2499,7 +2496,6 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) /* Make a copy, if the first transmission SKB clone we made * is still in somebody's hands, else make a clone. */ - TCP_SKB_CB(skb)->when = tcp_time_stamp; /* make sure skb->data is aligned on arches that require it * and check if ack-trimming & collapsing extended the headroom @@ -2544,7 +2540,7 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) /* Save stamp of the first retransmit. */ if (!tp->retrans_stamp) - tp->retrans_stamp = TCP_SKB_CB(skb)->when; + tp->retrans_stamp = tcp_skb_timestamp(skb); /* snd_nxt is stored to detect loss of retransmitted segment, * see tcp_input.c tcp_sacktag_write_queue(). @@ -2752,7 +2748,6 @@ void tcp_send_active_reset(struct sock *sk, gfp_t priority) tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk), TCPHDR_ACK | TCPHDR_RST); /* Send it off. */ - TCP_SKB_CB(skb)->when = tcp_time_stamp; if (tcp_transmit_skb(sk, skb, 0, priority)) NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED); @@ -2791,7 +2786,6 @@ int tcp_send_synack(struct sock *sk) TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK; TCP_ECN_send_synack(tcp_sk(sk), skb); } - TCP_SKB_CB(skb)->when = tcp_time_stamp; return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); } @@ -2835,10 +2829,10 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, memset(&opts, 0, sizeof(opts)); #ifdef CONFIG_SYN_COOKIES if (unlikely(req->cookie_ts)) - TCP_SKB_CB(skb)->when = cookie_init_timestamp(req); + skb->skb_mstamp.stamp_jiffies = cookie_init_timestamp(req); else #endif - TCP_SKB_CB(skb)->when = tcp_time_stamp; + skb_mstamp_get(&skb->skb_mstamp); tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, &md5, foc) + sizeof(*th); @@ -3086,7 +3080,7 @@ int tcp_connect(struct sock *sk) skb_reserve(buff, MAX_TCP_HEADER); tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN); - tp->retrans_stamp = TCP_SKB_CB(buff)->when = tcp_time_stamp; + tp->retrans_stamp = tcp_time_stamp; tcp_connect_queue_skb(sk, buff); TCP_ECN_send_syn(sk, buff); @@ -3194,7 +3188,7 @@ void tcp_send_ack(struct sock *sk) tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK); /* Send it off, this clears delayed acks for us. */ - TCP_SKB_CB(buff)->when = tcp_time_stamp; + skb_mstamp_get(&buff->skb_mstamp); tcp_transmit_skb(sk, buff, 0, sk_gfp_atomic(sk, GFP_ATOMIC)); } @@ -3226,7 +3220,7 @@ static int tcp_xmit_probe_skb(struct sock *sk, int urgent) * send it. */ tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK); - TCP_SKB_CB(skb)->when = tcp_time_stamp; + skb_mstamp_get(&skb->skb_mstamp); return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC); } @@ -3270,7 +3264,6 @@ int tcp_write_wakeup(struct sock *sk) tcp_set_skb_tso_segs(sk, skb, mss); TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH; - TCP_SKB_CB(skb)->when = tcp_time_stamp; err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); if (!err) tcp_event_new_data_sent(sk, skb); diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index df90cd1ce37..a339e7ba05a 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -135,10 +135,9 @@ static bool retransmits_timed_out(struct sock *sk, if (!inet_csk(sk)->icsk_retransmits) return false; - if (unlikely(!tcp_sk(sk)->retrans_stamp)) - start_ts = TCP_SKB_CB(tcp_write_queue_head(sk))->when; - else - start_ts = tcp_sk(sk)->retrans_stamp; + start_ts = tcp_sk(sk)->retrans_stamp; + if (unlikely(!start_ts)) + start_ts = tcp_skb_timestamp(tcp_write_queue_head(sk)); if (likely(timeout == 0)) { linear_backoff_thresh = ilog2(TCP_RTO_MAX/rto_base); -- cgit v1.2.3-70-g09d2 From 87d943085b76c6f07807dbc9fde2aad88e828590 Mon Sep 17 00:00:00 2001 From: Neal Cardwell Date: Sat, 6 Sep 2014 11:18:20 -0400 Subject: tcp: remove obsolete comment about TCP_SKB_CB(skb)->when in tcp_fragment() The TCP_SKB_CB(skb)->when field no longer exists as of recent change 7faee5c0d514 ("tcp: remove TCP_SKB_CB(skb)->when"). And in any case, tcp_fragment() is called on already-transmitted packets from the __tcp_retransmit_skb() call site, so copying timestamps of any kind in this spot is quite sensible. Signed-off-by: Neal Cardwell Reported-by: Yuchung Cheng Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 3 --- 1 file changed, 3 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 3b22dcb7bb5..7f1280dcad5 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1146,9 +1146,6 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, buff->ip_summed = skb->ip_summed; - /* Looks stupid, but our code really uses when of - * skbs, which it never sent before. --ANK - */ buff->tstamp = skb->tstamp; tcp_fragment_tstamp(skb, buff); -- cgit v1.2.3-70-g09d2 From fcdd1cf4dd63aecf86c987d7f4ec7187be5c2fbc Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 22 Sep 2014 13:19:44 -0700 Subject: tcp: avoid possible arithmetic overflows icsk_rto is a 32bit field, and icsk_backoff can reach 15 by default, or more if some sysctl (eg tcp_retries2) are changed. Better use 64bit to perform icsk_rto << icsk_backoff operations As Joe Perches suggested, add a helper for this. Yuchung spotted the tcp_v4_err() case. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/inet_connection_sock.h | 9 +++++++++ net/ipv4/tcp_input.c | 5 +++-- net/ipv4/tcp_ipv4.c | 6 +++--- net/ipv4/tcp_output.c | 13 ++++++------- net/ipv4/tcp_timer.c | 4 ++-- 5 files changed, 23 insertions(+), 14 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h index 5fbe6568c3c..848e85cb5c6 100644 --- a/include/net/inet_connection_sock.h +++ b/include/net/inet_connection_sock.h @@ -242,6 +242,15 @@ static inline void inet_csk_reset_xmit_timer(struct sock *sk, const int what, #endif } +static inline unsigned long +inet_csk_rto_backoff(const struct inet_connection_sock *icsk, + unsigned long max_when) +{ + u64 when = (u64)icsk->icsk_rto << icsk->icsk_backoff; + + return (unsigned long)min_t(u64, when, max_when); +} + struct sock *inet_csk_accept(struct sock *sk, int flags, int *err); struct request_sock *inet_csk_search_req(const struct sock *sk, diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 02fb66d4a01..13f3da4762e 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3208,9 +3208,10 @@ static void tcp_ack_probe(struct sock *sk) * This function is not for random using! */ } else { + unsigned long when = inet_csk_rto_backoff(icsk, TCP_RTO_MAX); + inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, - min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), - TCP_RTO_MAX); + when, TCP_RTO_MAX); } } diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 006b045716d..3b2e49cb2b6 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -430,9 +430,9 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info) break; icsk->icsk_backoff--; - inet_csk(sk)->icsk_rto = (tp->srtt_us ? __tcp_set_rto(tp) : - TCP_TIMEOUT_INIT) << icsk->icsk_backoff; - tcp_bound_rto(sk); + icsk->icsk_rto = tp->srtt_us ? __tcp_set_rto(tp) : + TCP_TIMEOUT_INIT; + icsk->icsk_rto = inet_csk_rto_backoff(icsk, TCP_RTO_MAX); skb = tcp_write_queue_head(sk); BUG_ON(!skb); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 7f1280dcad5..8c61a7c0c88 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -3279,6 +3279,7 @@ void tcp_send_probe0(struct sock *sk) { struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_sock *tp = tcp_sk(sk); + unsigned long probe_max; int err; err = tcp_write_wakeup(sk); @@ -3294,9 +3295,7 @@ void tcp_send_probe0(struct sock *sk) if (icsk->icsk_backoff < sysctl_tcp_retries2) icsk->icsk_backoff++; icsk->icsk_probes_out++; - inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, - min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), - TCP_RTO_MAX); + probe_max = TCP_RTO_MAX; } else { /* If packet was not sent due to local congestion, * do not backoff and do not remember icsk_probes_out. @@ -3306,11 +3305,11 @@ void tcp_send_probe0(struct sock *sk) */ if (!icsk->icsk_probes_out) icsk->icsk_probes_out = 1; - inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, - min(icsk->icsk_rto << icsk->icsk_backoff, - TCP_RESOURCE_PROBE_INTERVAL), - TCP_RTO_MAX); + probe_max = TCP_RESOURCE_PROBE_INTERVAL; } + inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, + inet_csk_rto_backoff(icsk, probe_max), + TCP_RTO_MAX); } int tcp_rtx_synack(struct sock *sk, struct request_sock *req) diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index a339e7ba05a..b24360f6e29 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -180,7 +180,7 @@ static int tcp_write_timeout(struct sock *sk) retry_until = sysctl_tcp_retries2; if (sock_flag(sk, SOCK_DEAD)) { - const int alive = (icsk->icsk_rto < TCP_RTO_MAX); + const int alive = icsk->icsk_rto < TCP_RTO_MAX; retry_until = tcp_orphan_retries(sk, alive); do_reset = alive || @@ -294,7 +294,7 @@ static void tcp_probe_timer(struct sock *sk) max_probes = sysctl_tcp_retries2; if (sock_flag(sk, SOCK_DEAD)) { - const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX); + const int alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX; max_probes = tcp_orphan_retries(sk, alive); -- cgit v1.2.3-70-g09d2 From f4a775d14489a801a5b8b0540e23ab82e2703091 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 22 Sep 2014 16:29:32 -0700 Subject: net: introduce __skb_header_release() While profiling TCP stack, I noticed one useless atomic operation in tcp_sendmsg(), caused by skb_header_release(). It turns out all current skb_header_release() users have a fresh skb, that no other user can see, so we can avoid one atomic operation. Introduce __skb_header_release() to clearly document this. This gave me a 1.5 % improvement on TCP_RR workload. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/skbuff.h | 15 +++++++++++++++ net/core/skbuff.c | 4 ++-- net/ipv4/tcp.c | 4 ++-- net/ipv4/tcp_output.c | 10 +++++----- 4 files changed, 24 insertions(+), 9 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index f1bfa3781c7..8eaa62400fc 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1083,6 +1083,7 @@ static inline int skb_header_cloned(const struct sk_buff *skb) * Drop a reference to the header part of the buffer. This is done * by acquiring a payload reference. You must not read from the header * part of skb->data after this. + * Note : Check if you can use __skb_header_release() instead. */ static inline void skb_header_release(struct sk_buff *skb) { @@ -1091,6 +1092,20 @@ static inline void skb_header_release(struct sk_buff *skb) atomic_add(1 << SKB_DATAREF_SHIFT, &skb_shinfo(skb)->dataref); } +/** + * __skb_header_release - release reference to header + * @skb: buffer to operate on + * + * Variant of skb_header_release() assuming skb is private to caller. + * We can avoid one atomic operation. + */ +static inline void __skb_header_release(struct sk_buff *skb) +{ + skb->nohdr = 1; + atomic_set(&skb_shinfo(skb)->dataref, 1 + (1 << SKB_DATAREF_SHIFT)); +} + + /** * skb_shared - is the buffer shared * @skb: buffer to check diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 06a8feb1009..512dc7dcbc3 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3179,7 +3179,7 @@ int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb) skb_shinfo(nskb)->frag_list = p; skb_shinfo(nskb)->gso_size = pinfo->gso_size; pinfo->gso_size = 0; - skb_header_release(p); + __skb_header_release(p); NAPI_GRO_CB(nskb)->last = p; nskb->data_len += p->len; @@ -3211,7 +3211,7 @@ merge: else NAPI_GRO_CB(p)->last->next = skb; NAPI_GRO_CB(p)->last = skb; - skb_header_release(skb); + __skb_header_release(skb); lp = p; done: diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 070aeff1b13..553b01f52f7 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -609,7 +609,7 @@ static inline bool forced_push(const struct tcp_sock *tp) return after(tp->write_seq, tp->pushed_seq + (tp->max_window >> 1)); } -static inline void skb_entail(struct sock *sk, struct sk_buff *skb) +static void skb_entail(struct sock *sk, struct sk_buff *skb) { struct tcp_sock *tp = tcp_sk(sk); struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); @@ -618,7 +618,7 @@ static inline void skb_entail(struct sock *sk, struct sk_buff *skb) tcb->seq = tcb->end_seq = tp->write_seq; tcb->tcp_flags = TCPHDR_ACK; tcb->sacked = 0; - skb_header_release(skb); + __skb_header_release(skb); tcp_add_write_queue_tail(sk, skb); sk->sk_wmem_queued += skb->truesize; sk_mem_charge(sk, skb->truesize); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 8c61a7c0c88..f173b1c4f81 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -995,7 +995,7 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) /* Advance write_seq and place onto the write_queue. */ tp->write_seq = TCP_SKB_CB(skb)->end_seq; - skb_header_release(skb); + __skb_header_release(skb); tcp_add_write_queue_tail(sk, skb); sk->sk_wmem_queued += skb->truesize; sk_mem_charge(sk, skb->truesize); @@ -1167,7 +1167,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, } /* Link BUFF into the send queue. */ - skb_header_release(buff); + __skb_header_release(buff); tcp_insert_write_queue_after(skb, buff, sk); return 0; @@ -1671,7 +1671,7 @@ static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, tcp_set_skb_tso_segs(sk, buff, mss_now); /* Link BUFF into the send queue. */ - skb_header_release(buff); + __skb_header_release(buff); tcp_insert_write_queue_after(skb, buff, sk); return 0; @@ -2772,7 +2772,7 @@ int tcp_send_synack(struct sock *sk) if (nskb == NULL) return -ENOMEM; tcp_unlink_write_queue(skb, sk); - skb_header_release(nskb); + __skb_header_release(nskb); __tcp_add_write_queue_head(sk, nskb); sk_wmem_free_skb(sk, skb); sk->sk_wmem_queued += nskb->truesize; @@ -2947,7 +2947,7 @@ static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb) struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); tcb->end_seq += skb->len; - skb_header_release(skb); + __skb_header_release(skb); __tcp_add_write_queue_tail(sk, skb); sk->sk_wmem_queued += skb->truesize; sk_mem_charge(sk, skb->truesize); -- cgit v1.2.3-70-g09d2 From 971f10eca186cab238c49daa91f703c5a001b0b1 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 27 Sep 2014 09:50:57 -0700 Subject: tcp: better TCP_SKB_CB layout to reduce cache line misses TCP maintains lists of skb in write queue, and in receive queues (in order and out of order queues) Scanning these lists both in input and output path usually requires access to skb->next, TCP_SKB_CB(skb)->seq, and TCP_SKB_CB(skb)->end_seq These fields are currently in two different cache lines, meaning we waste lot of memory bandwidth when these queues are big and flows have either packet drops or packet reorders. We can move TCP_SKB_CB(skb)->header at the end of TCP_SKB_CB, because this header is not used in fast path. This allows TCP to search much faster in the skb lists. Even with regular flows, we save one cache line miss in fast path. Thanks to Christoph Paasch for noticing we need to cleanup skb->cb[] (IPCB/IP6CB) before entering IP stack in tx path, and that I forgot IPCB use in tcp_v4_hnd_req() and tcp_v4_save_options(). Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/tcp.h | 12 ++++++------ net/ipv4/tcp_ipv4.c | 19 ++++++++++++------- net/ipv4/tcp_output.c | 5 +++++ net/ipv6/tcp_ipv6.c | 7 +++++++ 4 files changed, 30 insertions(+), 13 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/include/net/tcp.h b/include/net/tcp.h index a4201ef216e..4dc6641ee99 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -696,12 +696,6 @@ static inline u32 tcp_skb_timestamp(const struct sk_buff *skb) * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately. */ struct tcp_skb_cb { - union { - struct inet_skb_parm h4; -#if IS_ENABLED(CONFIG_IPV6) - struct inet6_skb_parm h6; -#endif - } header; /* For incoming frames */ __u32 seq; /* Starting sequence number */ __u32 end_seq; /* SEQ + FIN + SYN + datalen */ __u32 tcp_tw_isn; /* isn chosen by tcp_timewait_state_process() */ @@ -720,6 +714,12 @@ struct tcp_skb_cb { __u8 ip_dsfield; /* IPv4 tos or IPv6 dsfield */ /* 1 byte hole */ __u32 ack_seq; /* Sequence number ACK'd */ + union { + struct inet_skb_parm h4; +#if IS_ENABLED(CONFIG_IPV6) + struct inet6_skb_parm h6; +#endif + } header; /* For incoming frames */ }; #define TCP_SKB_CB(__skb) ((struct tcp_skb_cb *)&((__skb)->cb[0])) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 28ab90382c0..9ce3eac0295 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -886,18 +886,16 @@ EXPORT_SYMBOL(tcp_syn_flood_action); */ static struct ip_options_rcu *tcp_v4_save_options(struct sk_buff *skb) { - const struct ip_options *opt = &(IPCB(skb)->opt); + const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt; struct ip_options_rcu *dopt = NULL; if (opt && opt->optlen) { int opt_size = sizeof(*dopt) + opt->optlen; dopt = kmalloc(opt_size, GFP_ATOMIC); - if (dopt) { - if (ip_options_echo(&dopt->opt, skb)) { - kfree(dopt); - dopt = NULL; - } + if (dopt && __ip_options_echo(&dopt->opt, skb, opt)) { + kfree(dopt); + dopt = NULL; } } return dopt; @@ -1431,7 +1429,7 @@ static struct sock *tcp_v4_hnd_req(struct sock *sk, struct sk_buff *skb) #ifdef CONFIG_SYN_COOKIES if (!th->syn) - sk = cookie_v4_check(sk, skb, &(IPCB(skb)->opt)); + sk = cookie_v4_check(sk, skb, &TCP_SKB_CB(skb)->header.h4.opt); #endif return sk; } @@ -1636,6 +1634,13 @@ int tcp_v4_rcv(struct sk_buff *skb) th = tcp_hdr(skb); iph = ip_hdr(skb); + /* This is tricky : We move IPCB at its correct location into TCP_SKB_CB() + * barrier() makes sure compiler wont play fool^Waliasing games. + */ + memmove(&TCP_SKB_CB(skb)->header.h4, IPCB(skb), + sizeof(struct inet_skb_parm)); + barrier(); + TCP_SKB_CB(skb)->seq = ntohl(th->seq); TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin + skb->len - th->doff * 4); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index f173b1c4f81..a462fb1db89 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -974,6 +974,11 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, /* Our usage of tstamp should remain private */ skb->tstamp.tv64 = 0; + + /* Cleanup our debris for IP stacks */ + memset(skb->cb, 0, max(sizeof(struct inet_skb_parm), + sizeof(struct inet6_skb_parm))); + err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl); if (likely(err <= 0)) diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 9400b4326f2..132bac137ae 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1412,6 +1412,13 @@ static int tcp_v6_rcv(struct sk_buff *skb) th = tcp_hdr(skb); hdr = ipv6_hdr(skb); + /* This is tricky : We move IPCB at its correct location into TCP_SKB_CB() + * barrier() makes sure compiler wont play fool^Waliasing games. + */ + memmove(&TCP_SKB_CB(skb)->header.h6, IP6CB(skb), + sizeof(struct inet6_skb_parm)); + barrier(); + TCP_SKB_CB(skb)->seq = ntohl(th->seq); TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin + skb->len - th->doff*4); -- cgit v1.2.3-70-g09d2 From cd7d8498c9a5d510c64db38d9f4f4fbc41790f09 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 24 Sep 2014 04:11:22 -0700 Subject: tcp: change tcp_skb_pcount() location Our goal is to access no more than one cache line access per skb in a write or receive queue when doing the various walks. After recent TCP_SKB_CB() reorganizations, it is almost done. Last part is tcp_skb_pcount() which currently uses skb_shinfo(skb)->gso_segs, which is a terrible choice, because it needs 3 cache lines in current kernel (skb->head, skb->end, and shinfo->gso_segs are all in 3 different cache lines, far from skb->cb) This very simple patch reuses space currently taken by tcp_tw_isn only in input path, as tcp_skb_pcount is only needed for skb stored in write queue. This considerably speeds up tcp_ack(), granted we avoid shinfo->tx_flags to get SKBTX_ACK_TSTAMP, which seems possible. This also speeds up all sack processing in general. This speeds up tcp_sendmsg() because it no longer has to access/dirty shinfo. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/tcp.h | 23 +++++++++++++++++++++-- net/ipv4/tcp.c | 4 ++-- net/ipv4/tcp_input.c | 8 ++++---- net/ipv4/tcp_output.c | 9 ++++++--- 4 files changed, 33 insertions(+), 11 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/include/net/tcp.h b/include/net/tcp.h index 4dc6641ee99..02a9a2c366b 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -698,7 +698,16 @@ static inline u32 tcp_skb_timestamp(const struct sk_buff *skb) struct tcp_skb_cb { __u32 seq; /* Starting sequence number */ __u32 end_seq; /* SEQ + FIN + SYN + datalen */ - __u32 tcp_tw_isn; /* isn chosen by tcp_timewait_state_process() */ + union { + /* Note : tcp_tw_isn is used in input path only + * (isn chosen by tcp_timewait_state_process()) + * + * tcp_gso_segs is used in write queue only, + * cf tcp_skb_pcount() + */ + __u32 tcp_tw_isn; + __u32 tcp_gso_segs; + }; __u8 tcp_flags; /* TCP header flags. (tcp[13]) */ __u8 sacked; /* State flags for SACK/FACK. */ @@ -746,7 +755,17 @@ TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb, */ static inline int tcp_skb_pcount(const struct sk_buff *skb) { - return skb_shinfo(skb)->gso_segs; + return TCP_SKB_CB(skb)->tcp_gso_segs; +} + +static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs) +{ + TCP_SKB_CB(skb)->tcp_gso_segs = segs; +} + +static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs) +{ + TCP_SKB_CB(skb)->tcp_gso_segs += segs; } /* This is valid iff tcp_skb_pcount() > 1. */ diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 553b01f52f7..87289e51be0 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -963,7 +963,7 @@ new_segment: skb->ip_summed = CHECKSUM_PARTIAL; tp->write_seq += copy; TCP_SKB_CB(skb)->end_seq += copy; - skb_shinfo(skb)->gso_segs = 0; + tcp_skb_pcount_set(skb, 0); if (!copied) TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH; @@ -1261,7 +1261,7 @@ new_segment: tp->write_seq += copy; TCP_SKB_CB(skb)->end_seq += copy; - skb_shinfo(skb)->gso_segs = 0; + tcp_skb_pcount_set(skb, 0); from += copy; copied += copy; diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index f3f016a15c5..2c0af90231c 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1295,9 +1295,9 @@ static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb, TCP_SKB_CB(prev)->end_seq += shifted; TCP_SKB_CB(skb)->seq += shifted; - skb_shinfo(prev)->gso_segs += pcount; - BUG_ON(skb_shinfo(skb)->gso_segs < pcount); - skb_shinfo(skb)->gso_segs -= pcount; + tcp_skb_pcount_add(prev, pcount); + BUG_ON(tcp_skb_pcount(skb) < pcount); + tcp_skb_pcount_add(skb, -pcount); /* When we're adding to gso_segs == 1, gso_size will be zero, * in theory this shouldn't be necessary but as long as DSACK @@ -1310,7 +1310,7 @@ static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb, } /* CHECKME: To clear or not to clear? Mimics normal skb currently */ - if (skb_shinfo(skb)->gso_segs <= 1) { + if (tcp_skb_pcount(skb) <= 1) { skb_shinfo(skb)->gso_size = 0; skb_shinfo(skb)->gso_type = 0; } diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index a462fb1db89..4d92703df4c 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -384,7 +384,7 @@ static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags) TCP_SKB_CB(skb)->tcp_flags = flags; TCP_SKB_CB(skb)->sacked = 0; - shinfo->gso_segs = 1; + tcp_skb_pcount_set(skb, 1); shinfo->gso_size = 0; shinfo->gso_type = 0; @@ -972,6 +972,9 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS, tcp_skb_pcount(skb)); + /* OK, its time to fill skb_shinfo(skb)->gso_segs */ + skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb); + /* Our usage of tstamp should remain private */ skb->tstamp.tv64 = 0; @@ -1019,11 +1022,11 @@ static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb, /* Avoid the costly divide in the normal * non-TSO case. */ - shinfo->gso_segs = 1; + tcp_skb_pcount_set(skb, 1); shinfo->gso_size = 0; shinfo->gso_type = 0; } else { - shinfo->gso_segs = DIV_ROUND_UP(skb->len, mss_now); + tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now)); shinfo->gso_size = mss_now; shinfo->gso_type = sk->sk_gso_type; } -- cgit v1.2.3-70-g09d2 From 30e502a34b8b21fae2c789da102bd9f6e99fef83 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Fri, 26 Sep 2014 22:37:33 +0200 Subject: net: tcp: add flag for ca to indicate that ECN is required This patch adds a flag to TCP congestion algorithms that allows for requesting to mark IPv4/IPv6 sockets with transport as ECN capable, that is, ECT(0), when required by a congestion algorithm. It is currently used and needed in DataCenter TCP (DCTCP), as it requires both peers to assert ECT on all IP packets sent - it uses ECN feedback (i.e. CE, Congestion Encountered information) from switches inside the data center to derive feedback to the end hosts. Therefore, simply add a new flag to icsk_ca_ops. Note that DCTCP's algorithm/behaviour slightly diverges from RFC3168, therefore this is only (!) enabled iff the assigned congestion control ops module has requested this. By that, we can tightly couple this logic really only to the provided congestion control ops. Joint work with Florian Westphal and Glenn Judd. Signed-off-by: Daniel Borkmann Signed-off-by: Florian Westphal Signed-off-by: Glenn Judd Acked-by: Stephen Hemminger Signed-off-by: David S. Miller --- include/net/tcp.h | 61 +++++++++++++++++++++++++++++++++++++-------------- net/ipv4/tcp_input.c | 2 +- net/ipv4/tcp_output.c | 25 +++++++++++++++------ 3 files changed, 63 insertions(+), 25 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/include/net/tcp.h b/include/net/tcp.h index f99b0c072ee..a12f145cfbc 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -733,23 +733,6 @@ struct tcp_skb_cb { #define TCP_SKB_CB(__skb) ((struct tcp_skb_cb *)&((__skb)->cb[0])) -/* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set - * - * If we receive a SYN packet with these bits set, it means a network is - * playing bad games with TOS bits. In order to avoid possible false congestion - * notifications, we disable TCP ECN negociation. - */ -static inline void -TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb, - struct net *net) -{ - const struct tcphdr *th = tcp_hdr(skb); - - if (net->ipv4.sysctl_tcp_ecn && th->ece && th->cwr && - INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield)) - inet_rsk(req)->ecn_ok = 1; -} - /* Due to TSO, an SKB can be composed of multiple actual * packets. To keep these tracked properly, we use this. */ @@ -791,7 +774,10 @@ enum tcp_ca_event { #define TCP_CA_MAX 128 #define TCP_CA_BUF_MAX (TCP_CA_NAME_MAX*TCP_CA_MAX) +/* Algorithm can be set on socket without CAP_NET_ADMIN privileges */ #define TCP_CONG_NON_RESTRICTED 0x1 +/* Requires ECN/ECT set on all packets */ +#define TCP_CONG_NEEDS_ECN 0x2 struct tcp_congestion_ops { struct list_head list; @@ -840,6 +826,13 @@ u32 tcp_reno_ssthresh(struct sock *sk); void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked); extern struct tcp_congestion_ops tcp_reno; +static inline bool tcp_ca_needs_ecn(const struct sock *sk) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); + + return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN; +} + static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state) { struct inet_connection_sock *icsk = inet_csk(sk); @@ -857,6 +850,40 @@ static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event) icsk->icsk_ca_ops->cwnd_event(sk, event); } +/* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set + * + * If we receive a SYN packet with these bits set, it means a + * network is playing bad games with TOS bits. In order to + * avoid possible false congestion notifications, we disable + * TCP ECN negociation. + * + * Exception: tcp_ca wants ECN. This is required for DCTCP + * congestion control; it requires setting ECT on all packets, + * including SYN. We inverse the test in this case: If our + * local socket wants ECN, but peer only set ece/cwr (but not + * ECT in IP header) its probably a non-DCTCP aware sender. + */ +static inline void +TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb, + const struct sock *listen_sk) +{ + const struct tcphdr *th = tcp_hdr(skb); + const struct net *net = sock_net(listen_sk); + bool th_ecn = th->ece && th->cwr; + bool ect, need_ecn; + + if (!th_ecn) + return; + + ect = !INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield); + need_ecn = tcp_ca_needs_ecn(listen_sk); + + if (!ect && !need_ecn && net->ipv4.sysctl_tcp_ecn) + inet_rsk(req)->ecn_ok = 1; + else if (ect && need_ecn) + inet_rsk(req)->ecn_ok = 1; +} + /* These functions determine how the current flow behaves in respect of SACK * handling. SACK is negotiated with the peer, and therefore it can vary * between different flows. diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 5073eefa6fa..fb0fe97e1c5 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5944,7 +5944,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, goto drop_and_free; if (!want_cookie || tmp_opt.tstamp_ok) - TCP_ECN_create_request(req, skb, sock_net(sk)); + TCP_ECN_create_request(req, skb, sk); if (want_cookie) { isn = cookie_init_sequence(af_ops, sk, skb, &req->mss); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 4d92703df4c..20e73271d75 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -318,11 +318,15 @@ static u16 tcp_select_window(struct sock *sk) } /* Packet ECN state for a SYN-ACK */ -static inline void TCP_ECN_send_synack(const struct tcp_sock *tp, struct sk_buff *skb) +static inline void TCP_ECN_send_synack(struct sock *sk, struct sk_buff *skb) { + const struct tcp_sock *tp = tcp_sk(sk); + TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR; if (!(tp->ecn_flags & TCP_ECN_OK)) TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE; + else if (tcp_ca_needs_ecn(sk)) + INET_ECN_xmit(sk); } /* Packet ECN state for a SYN. */ @@ -331,17 +335,24 @@ static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb) struct tcp_sock *tp = tcp_sk(sk); tp->ecn_flags = 0; - if (sock_net(sk)->ipv4.sysctl_tcp_ecn == 1) { + if (sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 || + tcp_ca_needs_ecn(sk)) { TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR; tp->ecn_flags = TCP_ECN_OK; + if (tcp_ca_needs_ecn(sk)) + INET_ECN_xmit(sk); } } static __inline__ void -TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th) +TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th, + struct sock *sk) { - if (inet_rsk(req)->ecn_ok) + if (inet_rsk(req)->ecn_ok) { th->ece = 1; + if (tcp_ca_needs_ecn(sk)) + INET_ECN_xmit(sk); + } } /* Set up ECN state for a packet on a ESTABLISHED socket that is about to @@ -362,7 +373,7 @@ static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb, tcp_hdr(skb)->cwr = 1; skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN; } - } else { + } else if (!tcp_ca_needs_ecn(sk)) { /* ACK or retransmitted segment: clear ECT|CE */ INET_ECN_dontxmit(sk); } @@ -2789,7 +2800,7 @@ int tcp_send_synack(struct sock *sk) } TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK; - TCP_ECN_send_synack(tcp_sk(sk), skb); + TCP_ECN_send_synack(sk, skb); } return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); } @@ -2848,7 +2859,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, memset(th, 0, sizeof(struct tcphdr)); th->syn = 1; th->ack = 1; - TCP_ECN_make_synack(req, th); + TCP_ECN_make_synack(req, th, sk); th->source = htons(ireq->ir_num); th->dest = ireq->ir_rmt_port; /* Setting of flags are superfluous here for callers (and ECE is -- cgit v1.2.3-70-g09d2 From 9890092e46b2996bb85f7f973e69424cb5c07bc0 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Fri, 26 Sep 2014 22:37:35 +0200 Subject: net: tcp: more detailed ACK events and events for CE marked packets DataCenter TCP (DCTCP) determines cwnd growth based on ECN information and ACK properties, e.g. ACK that updates window is treated differently than DUPACK. Also DCTCP needs information whether ACK was delayed ACK. Furthermore, DCTCP also implements a CE state machine that keeps track of CE markings of incoming packets. Therefore, extend the congestion control framework to provide these event types, so that DCTCP can be properly implemented as a normal congestion algorithm module outside of the core stack. Joint work with Daniel Borkmann and Glenn Judd. Signed-off-by: Florian Westphal Signed-off-by: Daniel Borkmann Signed-off-by: Glenn Judd Acked-by: Stephen Hemminger Signed-off-by: David S. Miller --- include/net/tcp.h | 9 ++++++++- net/ipv4/tcp_input.c | 22 ++++++++++++++++++---- net/ipv4/tcp_output.c | 4 ++++ 3 files changed, 30 insertions(+), 5 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/include/net/tcp.h b/include/net/tcp.h index 7ec6a28305c..1f57c536349 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -763,10 +763,17 @@ enum tcp_ca_event { CA_EVENT_CWND_RESTART, /* congestion window restart */ CA_EVENT_COMPLETE_CWR, /* end of congestion recovery */ CA_EVENT_LOSS, /* loss timeout */ + CA_EVENT_ECN_NO_CE, /* ECT set, but not CE marked */ + CA_EVENT_ECN_IS_CE, /* received CE marked IP packet */ + CA_EVENT_DELAYED_ACK, /* Delayed ack is sent */ + CA_EVENT_NON_DELAYED_ACK, }; +/* Information about inbound ACK, passed to cong_ops->in_ack_event() */ enum tcp_ca_ack_event_flags { - CA_ACK_SLOWPATH = (1 << 0), + CA_ACK_SLOWPATH = (1 << 0), /* In slow path processing */ + CA_ACK_WIN_UPDATE = (1 << 1), /* ACK updated window */ + CA_ACK_ECE = (1 << 2), /* ECE bit is set on ack */ }; /* diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 8a38774cc66..fc133178c78 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -233,14 +233,21 @@ static inline void TCP_ECN_check_ce(struct tcp_sock *tp, const struct sk_buff *s tcp_enter_quickack_mode((struct sock *)tp); break; case INET_ECN_CE: + if (tcp_ca_needs_ecn((struct sock *)tp)) + tcp_ca_event((struct sock *)tp, CA_EVENT_ECN_IS_CE); + if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) { /* Better not delay acks, sender can have a very low cwnd */ tcp_enter_quickack_mode((struct sock *)tp); tp->ecn_flags |= TCP_ECN_DEMAND_CWR; } - /* fallinto */ + tp->ecn_flags |= TCP_ECN_SEEN; + break; default: + if (tcp_ca_needs_ecn((struct sock *)tp)) + tcp_ca_event((struct sock *)tp, CA_EVENT_ECN_NO_CE); tp->ecn_flags |= TCP_ECN_SEEN; + break; } } @@ -3429,10 +3436,12 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) tp->snd_una = ack; flag |= FLAG_WIN_UPDATE; - tcp_in_ack_event(sk, 0); + tcp_in_ack_event(sk, CA_ACK_WIN_UPDATE); NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS); } else { + u32 ack_ev_flags = CA_ACK_SLOWPATH; + if (ack_seq != TCP_SKB_CB(skb)->end_seq) flag |= FLAG_DATA; else @@ -3444,10 +3453,15 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una, &sack_rtt_us); - if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) + if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) { flag |= FLAG_ECE; + ack_ev_flags |= CA_ACK_ECE; + } + + if (flag & FLAG_WIN_UPDATE) + ack_ev_flags |= CA_ACK_WIN_UPDATE; - tcp_in_ack_event(sk, CA_ACK_SLOWPATH); + tcp_in_ack_event(sk, ack_ev_flags); } /* We passed data and got it acked, remove any soft error diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 20e73271d75..124f9e4e459 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -3130,6 +3130,8 @@ void tcp_send_delayed_ack(struct sock *sk) int ato = icsk->icsk_ack.ato; unsigned long timeout; + tcp_ca_event(sk, CA_EVENT_DELAYED_ACK); + if (ato > TCP_DELACK_MIN) { const struct tcp_sock *tp = tcp_sk(sk); int max_ato = HZ / 2; @@ -3186,6 +3188,8 @@ void tcp_send_ack(struct sock *sk) if (sk->sk_state == TCP_CLOSE) return; + tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK); + /* We are not putting this on the write queue, so * tcp_transmit_skb() will set the ownership to this * sock. -- cgit v1.2.3-70-g09d2 From e3118e8359bb7c59555aca60c725106e6d78c5ce Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Fri, 26 Sep 2014 22:37:36 +0200 Subject: net: tcp: add DCTCP congestion control algorithm This work adds the DataCenter TCP (DCTCP) congestion control algorithm [1], which has been first published at SIGCOMM 2010 [2], resp. follow-up analysis at SIGMETRICS 2011 [3] (and also, more recently as an informational IETF draft available at [4]). DCTCP is an enhancement to the TCP congestion control algorithm for data center networks. Typical data center workloads are i.e. i) partition/aggregate (queries; bursty, delay sensitive), ii) short messages e.g. 50KB-1MB (for coordination and control state; delay sensitive), and iii) large flows e.g. 1MB-100MB (data update; throughput sensitive). DCTCP has therefore been designed for such environments to provide/achieve the following three requirements: * High burst tolerance (incast due to partition/aggregate) * Low latency (short flows, queries) * High throughput (continuous data updates, large file transfers) with commodity, shallow buffered switches The basic idea of its design consists of two fundamentals: i) on the switch side, packets are being marked when its internal queue length > threshold K (K is chosen so that a large enough headroom for marked traffic is still available in the switch queue); ii) the sender/host side maintains a moving average of the fraction of marked packets, so each RTT, F is being updated as follows: F := X / Y, where X is # of marked ACKs, Y is total # of ACKs alpha := (1 - g) * alpha + g * F, where g is a smoothing constant The resulting alpha (iow: probability that switch queue is congested) is then being used in order to adaptively decrease the congestion window W: W := (1 - (alpha / 2)) * W The means for receiving marked packets resp. marking them on switch side in DCTCP is the use of ECN. RFC3168 describes a mechanism for using Explicit Congestion Notification from the switch for early detection of congestion, rather than waiting for segment loss to occur. However, this method only detects the presence of congestion, not the *extent*. In the presence of mild congestion, it reduces the TCP congestion window too aggressively and unnecessarily affects the throughput of long flows [4]. DCTCP, as mentioned, enhances Explicit Congestion Notification (ECN) processing to estimate the fraction of bytes that encounter congestion, rather than simply detecting that some congestion has occurred. DCTCP then scales the TCP congestion window based on this estimate [4], thus it can derive multibit feedback from the information present in the single-bit sequence of marks in its control law. And thus act in *proportion* to the extent of congestion, not its *presence*. Switches therefore set the Congestion Experienced (CE) codepoint in packets when internal queue lengths exceed threshold K. Resulting, DCTCP delivers the same or better throughput than normal TCP, while using 90% less buffer space. It was found in [2] that DCTCP enables the applications to handle 10x the current background traffic, without impacting foreground traffic. Moreover, a 10x increase in foreground traffic did not cause any timeouts, and thus largely eliminates TCP incast collapse problems. The algorithm itself has already seen deployments in large production data centers since then. We did a long-term stress-test and analysis in a data center, short summary of our TCP incast tests with iperf compared to cubic: This test measured DCTCP throughput and latency and compared it with CUBIC throughput and latency for an incast scenario. In this test, 19 senders sent at maximum rate to a single receiver. The receiver simply ran iperf -s. The senders ran iperf -c -t 30. All senders started simultaneously (using local clocks synchronized by ntp). This test was repeated multiple times. Below shows the results from a single test. Other tests are similar. (DCTCP results were extremely consistent, CUBIC results show some variance induced by the TCP timeouts that CUBIC encountered.) For this test, we report statistics on the number of TCP timeouts, flow throughput, and traffic latency. 1) Timeouts (total over all flows, and per flow summaries): CUBIC DCTCP Total 3227 25 Mean 169.842 1.316 Median 183 1 Max 207 5 Min 123 0 Stddev 28.991 1.600 Timeout data is taken by measuring the net change in netstat -s "other TCP timeouts" reported. As a result, the timeout measurements above are not restricted to the test traffic, and we believe that it is likely that all of the "DCTCP timeouts" are actually timeouts for non-test traffic. We report them nevertheless. CUBIC will also include some non-test timeouts, but they are drawfed by bona fide test traffic timeouts for CUBIC. Clearly DCTCP does an excellent job of preventing TCP timeouts. DCTCP reduces timeouts by at least two orders of magnitude and may well have eliminated them in this scenario. 2) Throughput (per flow in Mbps): CUBIC DCTCP Mean 521.684 521.895 Median 464 523 Max 776 527 Min 403 519 Stddev 105.891 2.601 Fairness 0.962 0.999 Throughput data was simply the average throughput for each flow reported by iperf. By avoiding TCP timeouts, DCTCP is able to achieve much better per-flow results. In CUBIC, many flows experience TCP timeouts which makes flow throughput unpredictable and unfair. DCTCP, on the other hand, provides very clean predictable throughput without incurring TCP timeouts. Thus, the standard deviation of CUBIC throughput is dramatically higher than the standard deviation of DCTCP throughput. Mean throughput is nearly identical because even though cubic flows suffer TCP timeouts, other flows will step in and fill the unused bandwidth. Note that this test is something of a best case scenario for incast under CUBIC: it allows other flows to fill in for flows experiencing a timeout. Under situations where the receiver is issuing requests and then waiting for all flows to complete, flows cannot fill in for timed out flows and throughput will drop dramatically. 3) Latency (in ms): CUBIC DCTCP Mean 4.0088 0.04219 Median 4.055 0.0395 Max 4.2 0.085 Min 3.32 0.028 Stddev 0.1666 0.01064 Latency for each protocol was computed by running "ping -i 0.2 " from a single sender to the receiver during the incast test. For DCTCP, "ping -Q 0x6 -i 0.2 " was used to ensure that traffic traversed the DCTCP queue and was not dropped when the queue size was greater than the marking threshold. The summary statistics above are over all ping metrics measured between the single sender, receiver pair. The latency results for this test show a dramatic difference between CUBIC and DCTCP. CUBIC intentionally overflows the switch buffer which incurs the maximum queue latency (more buffer memory will lead to high latency.) DCTCP, on the other hand, deliberately attempts to keep queue occupancy low. The result is a two orders of magnitude reduction of latency with DCTCP - even with a switch with relatively little RAM. Switches with larger amounts of RAM will incur increasing amounts of latency for CUBIC, but not for DCTCP. 4) Convergence and stability test: This test measured the time that DCTCP took to fairly redistribute bandwidth when a new flow commences. It also measured DCTCP's ability to remain stable at a fair bandwidth distribution. DCTCP is compared with CUBIC for this test. At the commencement of this test, a single flow is sending at maximum rate (near 10 Gbps) to a single receiver. One second after that first flow commences, a new flow from a distinct server begins sending to the same receiver as the first flow. After the second flow has sent data for 10 seconds, the second flow is terminated. The first flow sends for an additional second. Ideally, the bandwidth would be evenly shared as soon as the second flow starts, and recover as soon as it stops. The results of this test are shown below. Note that the flow bandwidth for the two flows was measured near the same time, but not simultaneously. DCTCP performs nearly perfectly within the measurement limitations of this test: bandwidth is quickly distributed fairly between the two flows, remains stable throughout the duration of the test, and recovers quickly. CUBIC, in contrast, is slow to divide the bandwidth fairly, and has trouble remaining stable. CUBIC DCTCP Seconds Flow 1 Flow 2 Seconds Flow 1 Flow 2 0 9.93 0 0 9.92 0 0.5 9.87 0 0.5 9.86 0 1 8.73 2.25 1 6.46 4.88 1.5 7.29 2.8 1.5 4.9 4.99 2 6.96 3.1 2 4.92 4.94 2.5 6.67 3.34 2.5 4.93 5 3 6.39 3.57 3 4.92 4.99 3.5 6.24 3.75 3.5 4.94 4.74 4 6 3.94 4 5.34 4.71 4.5 5.88 4.09 4.5 4.99 4.97 5 5.27 4.98 5 4.83 5.01 5.5 4.93 5.04 5.5 4.89 4.99 6 4.9 4.99 6 4.92 5.04 6.5 4.93 5.1 6.5 4.91 4.97 7 4.28 5.8 7 4.97 4.97 7.5 4.62 4.91 7.5 4.99 4.82 8 5.05 4.45 8 5.16 4.76 8.5 5.93 4.09 8.5 4.94 4.98 9 5.73 4.2 9 4.92 5.02 9.5 5.62 4.32 9.5 4.87 5.03 10 6.12 3.2 10 4.91 5.01 10.5 6.91 3.11 10.5 4.87 5.04 11 8.48 0 11 8.49 4.94 11.5 9.87 0 11.5 9.9 0 SYN/ACK ECT test: This test demonstrates the importance of ECT on SYN and SYN-ACK packets by measuring the connection probability in the presence of competing flows for a DCTCP connection attempt *without* ECT in the SYN packet. The test was repeated five times for each number of competing flows. Competing Flows 1 | 2 | 4 | 8 | 16 ------------------------------ Mean Connection Probability 1 | 0.67 | 0.45 | 0.28 | 0 Median Connection Probability 1 | 0.65 | 0.45 | 0.25 | 0 As the number of competing flows moves beyond 1, the connection probability drops rapidly. Enabling DCTCP with this patch requires the following steps: DCTCP must be running both on the sender and receiver side in your data center, i.e.: sysctl -w net.ipv4.tcp_congestion_control=dctcp Also, ECN functionality must be enabled on all switches in your data center for DCTCP to work. The default ECN marking threshold (K) heuristic on the switch for DCTCP is e.g., 20 packets (30KB) at 1Gbps, and 65 packets (~100KB) at 10Gbps (K > 1/7 * C * RTT, [4]). In above tests, for each switch port, traffic was segregated into two queues. For any packet with a DSCP of 0x01 - or equivalently a TOS of 0x04 - the packet was placed into the DCTCP queue. All other packets were placed into the default drop-tail queue. For the DCTCP queue, RED/ECN marking was enabled, here, with a marking threshold of 75 KB. More details however, we refer you to the paper [2] under section 3). There are no code changes required to applications running in user space. DCTCP has been implemented in full *isolation* of the rest of the TCP code as its own congestion control module, so that it can run without a need to expose code to the core of the TCP stack, and thus nothing changes for non-DCTCP users. Changes in the CA framework code are minimal, and DCTCP algorithm operates on mechanisms that are already available in most Silicon. The gain (dctcp_shift_g) is currently a fixed constant (1/16) from the paper, but we leave the option that it can be chosen carefully to a different value by the user. In case DCTCP is being used and ECN support on peer site is off, DCTCP falls back after 3WHS to operate in normal TCP Reno mode. ss {-4,-6} -t -i diag interface: ... dctcp wscale:7,7 rto:203 rtt:2.349/0.026 mss:1448 cwnd:2054 ssthresh:1102 ce_state 0 alpha 15 ab_ecn 0 ab_tot 735584 send 10129.2Mbps pacing_rate 20254.1Mbps unacked:1822 retrans:0/15 reordering:101 rcv_space:29200 ... dctcp-reno wscale:7,7 rto:201 rtt:0.711/1.327 ato:40 mss:1448 cwnd:10 ssthresh:1102 fallback_mode send 162.9Mbps pacing_rate 325.5Mbps rcv_rtt:1.5 rcv_space:29200 More information about DCTCP can be found in [1-4]. [1] http://simula.stanford.edu/~alizade/Site/DCTCP.html [2] http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp-final.pdf [3] http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp_analysis-full.pdf [4] http://tools.ietf.org/html/draft-bensley-tcpm-dctcp-00 Joint work with Florian Westphal and Glenn Judd. Signed-off-by: Daniel Borkmann Signed-off-by: Florian Westphal Signed-off-by: Glenn Judd Acked-by: Stephen Hemminger Signed-off-by: David S. Miller --- Documentation/networking/dctcp.txt | 43 +++++ include/uapi/linux/inet_diag.h | 13 +- net/ipv4/Kconfig | 26 ++- net/ipv4/Makefile | 1 + net/ipv4/tcp_dctcp.c | 344 +++++++++++++++++++++++++++++++++++++ net/ipv4/tcp_output.c | 1 + 6 files changed, 425 insertions(+), 3 deletions(-) create mode 100644 Documentation/networking/dctcp.txt create mode 100644 net/ipv4/tcp_dctcp.c (limited to 'net/ipv4/tcp_output.c') diff --git a/Documentation/networking/dctcp.txt b/Documentation/networking/dctcp.txt new file mode 100644 index 00000000000..0d5dfbc89ec --- /dev/null +++ b/Documentation/networking/dctcp.txt @@ -0,0 +1,43 @@ +DCTCP (DataCenter TCP) +---------------------- + +DCTCP is an enhancement to the TCP congestion control algorithm for data +center networks and leverages Explicit Congestion Notification (ECN) in +the data center network to provide multi-bit feedback to the end hosts. + +To enable it on end hosts: + + sysctl -w net.ipv4.tcp_congestion_control=dctcp + +All switches in the data center network running DCTCP must support ECN +marking and be configured for marking when reaching defined switch buffer +thresholds. The default ECN marking threshold heuristic for DCTCP on +switches is 20 packets (30KB) at 1Gbps, and 65 packets (~100KB) at 10Gbps, +but might need further careful tweaking. + +For more details, see below documents: + +Paper: + +The algorithm is further described in detail in the following two +SIGCOMM/SIGMETRICS papers: + + i) Mohammad Alizadeh, Albert Greenberg, David A. Maltz, Jitendra Padhye, + Parveen Patel, Balaji Prabhakar, Sudipta Sengupta, and Murari Sridharan: + "Data Center TCP (DCTCP)", Data Center Networks session + Proc. ACM SIGCOMM, New Delhi, 2010. + http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp-final.pdf + http://www.sigcomm.org/ccr/papers/2010/October/1851275.1851192 + +ii) Mohammad Alizadeh, Adel Javanmard, and Balaji Prabhakar: + "Analysis of DCTCP: Stability, Convergence, and Fairness" + Proc. ACM SIGMETRICS, San Jose, 2011. + http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp_analysis-full.pdf + +IETF informational draft: + + http://tools.ietf.org/html/draft-bensley-tcpm-dctcp-00 + +DCTCP site: + + http://simula.stanford.edu/~alizade/Site/DCTCP.html diff --git a/include/uapi/linux/inet_diag.h b/include/uapi/linux/inet_diag.h index bbde90fa583..d65c0a09efd 100644 --- a/include/uapi/linux/inet_diag.h +++ b/include/uapi/linux/inet_diag.h @@ -110,10 +110,10 @@ enum { INET_DIAG_TCLASS, INET_DIAG_SKMEMINFO, INET_DIAG_SHUTDOWN, + INET_DIAG_DCTCPINFO, }; -#define INET_DIAG_MAX INET_DIAG_SHUTDOWN - +#define INET_DIAG_MAX INET_DIAG_DCTCPINFO /* INET_DIAG_MEM */ @@ -133,5 +133,14 @@ struct tcpvegas_info { __u32 tcpv_minrtt; }; +/* INET_DIAG_DCTCPINFO */ + +struct tcp_dctcp_info { + __u16 dctcp_enabled; + __u16 dctcp_ce_state; + __u32 dctcp_alpha; + __u32 dctcp_ab_ecn; + __u32 dctcp_ab_tot; +}; #endif /* _UAPI_INET_DIAG_H_ */ diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig index 84f710b7472..69fb3785444 100644 --- a/net/ipv4/Kconfig +++ b/net/ipv4/Kconfig @@ -570,6 +570,27 @@ config TCP_CONG_ILLINOIS For further details see: http://www.ews.uiuc.edu/~shaoliu/tcpillinois/index.html +config TCP_CONG_DCTCP + tristate "DataCenter TCP (DCTCP)" + default n + ---help--- + DCTCP leverages Explicit Congestion Notification (ECN) in the network to + provide multi-bit feedback to the end hosts. It is designed to provide: + + - High burst tolerance (incast due to partition/aggregate), + - Low latency (short flows, queries), + - High throughput (continuous data updates, large file transfers) with + commodity, shallow-buffered switches. + + All switches in the data center network running DCTCP must support + ECN marking and be configured for marking when reaching defined switch + buffer thresholds. The default ECN marking threshold heuristic for + DCTCP on switches is 20 packets (30KB) at 1Gbps, and 65 packets + (~100KB) at 10Gbps, but might need further careful tweaking. + + For further details see: + http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp-final.pdf + choice prompt "Default TCP congestion control" default DEFAULT_CUBIC @@ -598,9 +619,11 @@ choice config DEFAULT_WESTWOOD bool "Westwood" if TCP_CONG_WESTWOOD=y + config DEFAULT_DCTCP + bool "DCTCP" if TCP_CONG_DCTCP=y + config DEFAULT_RENO bool "Reno" - endchoice endif @@ -620,6 +643,7 @@ config DEFAULT_TCP_CONG default "westwood" if DEFAULT_WESTWOOD default "veno" if DEFAULT_VENO default "reno" if DEFAULT_RENO + default "dctcp" if DEFAULT_DCTCP default "cubic" config TCP_MD5SIG diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile index d78d404c596..d8105787c19 100644 --- a/net/ipv4/Makefile +++ b/net/ipv4/Makefile @@ -43,6 +43,7 @@ obj-$(CONFIG_INET_UDP_DIAG) += udp_diag.o obj-$(CONFIG_NET_TCPPROBE) += tcp_probe.o obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o obj-$(CONFIG_TCP_CONG_CUBIC) += tcp_cubic.o +obj-$(CONFIG_TCP_CONG_DCTCP) += tcp_dctcp.o obj-$(CONFIG_TCP_CONG_WESTWOOD) += tcp_westwood.o obj-$(CONFIG_TCP_CONG_HSTCP) += tcp_highspeed.o obj-$(CONFIG_TCP_CONG_HYBLA) += tcp_hybla.o diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c new file mode 100644 index 00000000000..b504371af74 --- /dev/null +++ b/net/ipv4/tcp_dctcp.c @@ -0,0 +1,344 @@ +/* DataCenter TCP (DCTCP) congestion control. + * + * http://simula.stanford.edu/~alizade/Site/DCTCP.html + * + * This is an implementation of DCTCP over Reno, an enhancement to the + * TCP congestion control algorithm designed for data centers. DCTCP + * leverages Explicit Congestion Notification (ECN) in the network to + * provide multi-bit feedback to the end hosts. DCTCP's goal is to meet + * the following three data center transport requirements: + * + * - High burst tolerance (incast due to partition/aggregate) + * - Low latency (short flows, queries) + * - High throughput (continuous data updates, large file transfers) + * with commodity shallow buffered switches + * + * The algorithm is described in detail in the following two papers: + * + * 1) Mohammad Alizadeh, Albert Greenberg, David A. Maltz, Jitendra Padhye, + * Parveen Patel, Balaji Prabhakar, Sudipta Sengupta, and Murari Sridharan: + * "Data Center TCP (DCTCP)", Data Center Networks session + * Proc. ACM SIGCOMM, New Delhi, 2010. + * http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp-final.pdf + * + * 2) Mohammad Alizadeh, Adel Javanmard, and Balaji Prabhakar: + * "Analysis of DCTCP: Stability, Convergence, and Fairness" + * Proc. ACM SIGMETRICS, San Jose, 2011. + * http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp_analysis-full.pdf + * + * Initial prototype from Abdul Kabbani, Masato Yasuda and Mohammad Alizadeh. + * + * Authors: + * + * Daniel Borkmann + * Florian Westphal + * Glenn Judd + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or (at + * your option) any later version. + */ + +#include +#include +#include +#include + +#define DCTCP_MAX_ALPHA 1024U + +struct dctcp { + u32 acked_bytes_ecn; + u32 acked_bytes_total; + u32 prior_snd_una; + u32 prior_rcv_nxt; + u32 dctcp_alpha; + u32 next_seq; + u32 ce_state; + u32 delayed_ack_reserved; +}; + +static unsigned int dctcp_shift_g __read_mostly = 4; /* g = 1/2^4 */ +module_param(dctcp_shift_g, uint, 0644); +MODULE_PARM_DESC(dctcp_shift_g, "parameter g for updating dctcp_alpha"); + +static unsigned int dctcp_alpha_on_init __read_mostly = DCTCP_MAX_ALPHA; +module_param(dctcp_alpha_on_init, uint, 0644); +MODULE_PARM_DESC(dctcp_alpha_on_init, "parameter for initial alpha value"); + +static unsigned int dctcp_clamp_alpha_on_loss __read_mostly; +module_param(dctcp_clamp_alpha_on_loss, uint, 0644); +MODULE_PARM_DESC(dctcp_clamp_alpha_on_loss, + "parameter for clamping alpha on loss"); + +static struct tcp_congestion_ops dctcp_reno; + +static void dctcp_reset(const struct tcp_sock *tp, struct dctcp *ca) +{ + ca->next_seq = tp->snd_nxt; + + ca->acked_bytes_ecn = 0; + ca->acked_bytes_total = 0; +} + +static void dctcp_init(struct sock *sk) +{ + const struct tcp_sock *tp = tcp_sk(sk); + + if ((tp->ecn_flags & TCP_ECN_OK) || + (sk->sk_state == TCP_LISTEN || + sk->sk_state == TCP_CLOSE)) { + struct dctcp *ca = inet_csk_ca(sk); + + ca->prior_snd_una = tp->snd_una; + ca->prior_rcv_nxt = tp->rcv_nxt; + + ca->dctcp_alpha = min(dctcp_alpha_on_init, DCTCP_MAX_ALPHA); + + ca->delayed_ack_reserved = 0; + ca->ce_state = 0; + + dctcp_reset(tp, ca); + return; + } + + /* No ECN support? Fall back to Reno. Also need to clear + * ECT from sk since it is set during 3WHS for DCTCP. + */ + inet_csk(sk)->icsk_ca_ops = &dctcp_reno; + INET_ECN_dontxmit(sk); +} + +static u32 dctcp_ssthresh(struct sock *sk) +{ + const struct dctcp *ca = inet_csk_ca(sk); + struct tcp_sock *tp = tcp_sk(sk); + + return max(tp->snd_cwnd - ((tp->snd_cwnd * ca->dctcp_alpha) >> 11U), 2U); +} + +/* Minimal DCTP CE state machine: + * + * S: 0 <- last pkt was non-CE + * 1 <- last pkt was CE + */ + +static void dctcp_ce_state_0_to_1(struct sock *sk) +{ + struct dctcp *ca = inet_csk_ca(sk); + struct tcp_sock *tp = tcp_sk(sk); + + /* State has changed from CE=0 to CE=1 and delayed + * ACK has not sent yet. + */ + if (!ca->ce_state && ca->delayed_ack_reserved) { + u32 tmp_rcv_nxt; + + /* Save current rcv_nxt. */ + tmp_rcv_nxt = tp->rcv_nxt; + + /* Generate previous ack with CE=0. */ + tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; + tp->rcv_nxt = ca->prior_rcv_nxt; + + tcp_send_ack(sk); + + /* Recover current rcv_nxt. */ + tp->rcv_nxt = tmp_rcv_nxt; + } + + ca->prior_rcv_nxt = tp->rcv_nxt; + ca->ce_state = 1; + + tp->ecn_flags |= TCP_ECN_DEMAND_CWR; +} + +static void dctcp_ce_state_1_to_0(struct sock *sk) +{ + struct dctcp *ca = inet_csk_ca(sk); + struct tcp_sock *tp = tcp_sk(sk); + + /* State has changed from CE=1 to CE=0 and delayed + * ACK has not sent yet. + */ + if (ca->ce_state && ca->delayed_ack_reserved) { + u32 tmp_rcv_nxt; + + /* Save current rcv_nxt. */ + tmp_rcv_nxt = tp->rcv_nxt; + + /* Generate previous ack with CE=1. */ + tp->ecn_flags |= TCP_ECN_DEMAND_CWR; + tp->rcv_nxt = ca->prior_rcv_nxt; + + tcp_send_ack(sk); + + /* Recover current rcv_nxt. */ + tp->rcv_nxt = tmp_rcv_nxt; + } + + ca->prior_rcv_nxt = tp->rcv_nxt; + ca->ce_state = 0; + + tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; +} + +static void dctcp_update_alpha(struct sock *sk, u32 flags) +{ + const struct tcp_sock *tp = tcp_sk(sk); + struct dctcp *ca = inet_csk_ca(sk); + u32 acked_bytes = tp->snd_una - ca->prior_snd_una; + + /* If ack did not advance snd_una, count dupack as MSS size. + * If ack did update window, do not count it at all. + */ + if (acked_bytes == 0 && !(flags & CA_ACK_WIN_UPDATE)) + acked_bytes = inet_csk(sk)->icsk_ack.rcv_mss; + if (acked_bytes) { + ca->acked_bytes_total += acked_bytes; + ca->prior_snd_una = tp->snd_una; + + if (flags & CA_ACK_ECE) + ca->acked_bytes_ecn += acked_bytes; + } + + /* Expired RTT */ + if (!before(tp->snd_una, ca->next_seq)) { + /* For avoiding denominator == 1. */ + if (ca->acked_bytes_total == 0) + ca->acked_bytes_total = 1; + + /* alpha = (1 - g) * alpha + g * F */ + ca->dctcp_alpha = ca->dctcp_alpha - + (ca->dctcp_alpha >> dctcp_shift_g) + + (ca->acked_bytes_ecn << (10U - dctcp_shift_g)) / + ca->acked_bytes_total; + + if (ca->dctcp_alpha > DCTCP_MAX_ALPHA) + /* Clamp dctcp_alpha to max. */ + ca->dctcp_alpha = DCTCP_MAX_ALPHA; + + dctcp_reset(tp, ca); + } +} + +static void dctcp_state(struct sock *sk, u8 new_state) +{ + if (dctcp_clamp_alpha_on_loss && new_state == TCP_CA_Loss) { + struct dctcp *ca = inet_csk_ca(sk); + + /* If this extension is enabled, we clamp dctcp_alpha to + * max on packet loss; the motivation is that dctcp_alpha + * is an indicator to the extend of congestion and packet + * loss is an indicator of extreme congestion; setting + * this in practice turned out to be beneficial, and + * effectively assumes total congestion which reduces the + * window by half. + */ + ca->dctcp_alpha = DCTCP_MAX_ALPHA; + } +} + +static void dctcp_update_ack_reserved(struct sock *sk, enum tcp_ca_event ev) +{ + struct dctcp *ca = inet_csk_ca(sk); + + switch (ev) { + case CA_EVENT_DELAYED_ACK: + if (!ca->delayed_ack_reserved) + ca->delayed_ack_reserved = 1; + break; + case CA_EVENT_NON_DELAYED_ACK: + if (ca->delayed_ack_reserved) + ca->delayed_ack_reserved = 0; + break; + default: + /* Don't care for the rest. */ + break; + } +} + +static void dctcp_cwnd_event(struct sock *sk, enum tcp_ca_event ev) +{ + switch (ev) { + case CA_EVENT_ECN_IS_CE: + dctcp_ce_state_0_to_1(sk); + break; + case CA_EVENT_ECN_NO_CE: + dctcp_ce_state_1_to_0(sk); + break; + case CA_EVENT_DELAYED_ACK: + case CA_EVENT_NON_DELAYED_ACK: + dctcp_update_ack_reserved(sk, ev); + break; + default: + /* Don't care for the rest. */ + break; + } +} + +static void dctcp_get_info(struct sock *sk, u32 ext, struct sk_buff *skb) +{ + const struct dctcp *ca = inet_csk_ca(sk); + + /* Fill it also in case of VEGASINFO due to req struct limits. + * We can still correctly retrieve it later. + */ + if (ext & (1 << (INET_DIAG_DCTCPINFO - 1)) || + ext & (1 << (INET_DIAG_VEGASINFO - 1))) { + struct tcp_dctcp_info info; + + memset(&info, 0, sizeof(info)); + if (inet_csk(sk)->icsk_ca_ops != &dctcp_reno) { + info.dctcp_enabled = 1; + info.dctcp_ce_state = (u16) ca->ce_state; + info.dctcp_alpha = ca->dctcp_alpha; + info.dctcp_ab_ecn = ca->acked_bytes_ecn; + info.dctcp_ab_tot = ca->acked_bytes_total; + } + + nla_put(skb, INET_DIAG_DCTCPINFO, sizeof(info), &info); + } +} + +static struct tcp_congestion_ops dctcp __read_mostly = { + .init = dctcp_init, + .in_ack_event = dctcp_update_alpha, + .cwnd_event = dctcp_cwnd_event, + .ssthresh = dctcp_ssthresh, + .cong_avoid = tcp_reno_cong_avoid, + .set_state = dctcp_state, + .get_info = dctcp_get_info, + .flags = TCP_CONG_NEEDS_ECN, + .owner = THIS_MODULE, + .name = "dctcp", +}; + +static struct tcp_congestion_ops dctcp_reno __read_mostly = { + .ssthresh = tcp_reno_ssthresh, + .cong_avoid = tcp_reno_cong_avoid, + .get_info = dctcp_get_info, + .owner = THIS_MODULE, + .name = "dctcp-reno", +}; + +static int __init dctcp_register(void) +{ + BUILD_BUG_ON(sizeof(struct dctcp) > ICSK_CA_PRIV_SIZE); + return tcp_register_congestion_control(&dctcp); +} + +static void __exit dctcp_unregister(void) +{ + tcp_unregister_congestion_control(&dctcp); +} + +module_init(dctcp_register); +module_exit(dctcp_unregister); + +MODULE_AUTHOR("Daniel Borkmann "); +MODULE_AUTHOR("Florian Westphal "); +MODULE_AUTHOR("Glenn Judd "); + +MODULE_LICENSE("GPL v2"); +MODULE_DESCRIPTION("DataCenter TCP (DCTCP)"); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 124f9e4e459..86a0216fcaa 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -3211,6 +3211,7 @@ void tcp_send_ack(struct sock *sk) skb_mstamp_get(&buff->skb_mstamp); tcp_transmit_skb(sk, buff, 0, sk_gfp_atomic(sk, GFP_ATOMIC)); } +EXPORT_SYMBOL_GPL(tcp_send_ack); /* This routine sends a packet with an out of date sequence * number. It assumes the other end will try to ack it. -- cgit v1.2.3-70-g09d2 From 735d383117e113403442d971b23e7cfa2f876c7c Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Mon, 29 Sep 2014 13:08:30 +0200 Subject: tcp: change TCP_ECN prefixes to lower case Suggested by Stephen. Also drop inline keyword and let compiler decide. gcc 4.7.3 decides to no longer inline tcp_ecn_check_ce, so split it up. The actual evaluation is not inlined anymore while the ECN_OK test is. Suggested-by: Stephen Hemminger Signed-off-by: Daniel Borkmann Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 41 ++++++++++++++++++++++------------------- net/ipv4/tcp_minisocks.c | 6 +++--- net/ipv4/tcp_output.c | 18 +++++++++--------- 3 files changed, 34 insertions(+), 31 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 174181e28ef..aa38f98b788 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -201,28 +201,25 @@ static inline bool tcp_in_quickack_mode(const struct sock *sk) return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong; } -static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp) +static void tcp_ecn_queue_cwr(struct tcp_sock *tp) { if (tp->ecn_flags & TCP_ECN_OK) tp->ecn_flags |= TCP_ECN_QUEUE_CWR; } -static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, const struct sk_buff *skb) +static void tcp_ecn_accept_cwr(struct tcp_sock *tp, const struct sk_buff *skb) { if (tcp_hdr(skb)->cwr) tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; } -static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp) +static void tcp_ecn_withdraw_cwr(struct tcp_sock *tp) { tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; } -static inline void TCP_ECN_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) +static void __tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) { - if (!(tp->ecn_flags & TCP_ECN_OK)) - return; - switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) { case INET_ECN_NOT_ECT: /* Funny extension: if ECT is not set on a segment, @@ -251,19 +248,25 @@ static inline void TCP_ECN_check_ce(struct tcp_sock *tp, const struct sk_buff *s } } -static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th) +static void tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) +{ + if (tp->ecn_flags & TCP_ECN_OK) + __tcp_ecn_check_ce(tp, skb); +} + +static void tcp_ecn_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th) { if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr)) tp->ecn_flags &= ~TCP_ECN_OK; } -static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th) +static void tcp_ecn_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th) { if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr)) tp->ecn_flags &= ~TCP_ECN_OK; } -static bool TCP_ECN_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th) +static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th) { if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK)) return true; @@ -660,7 +663,7 @@ static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) } icsk->icsk_ack.lrcvtime = now; - TCP_ECN_check_ce(tp, skb); + tcp_ecn_check_ce(tp, skb); if (skb->len >= 128) tcp_grow_window(sk, skb); @@ -1976,7 +1979,7 @@ void tcp_enter_loss(struct sock *sk) sysctl_tcp_reordering); tcp_set_ca_state(sk, TCP_CA_Loss); tp->high_seq = tp->snd_nxt; - TCP_ECN_queue_cwr(tp); + tcp_ecn_queue_cwr(tp); /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous * loss recovery is underway except recurring timeout(s) on @@ -2368,7 +2371,7 @@ static void tcp_undo_cwnd_reduction(struct sock *sk, bool unmark_loss) if (tp->prior_ssthresh > tp->snd_ssthresh) { tp->snd_ssthresh = tp->prior_ssthresh; - TCP_ECN_withdraw_cwr(tp); + tcp_ecn_withdraw_cwr(tp); } } else { tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); @@ -2498,7 +2501,7 @@ static void tcp_init_cwnd_reduction(struct sock *sk) tp->prr_delivered = 0; tp->prr_out = 0; tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk); - TCP_ECN_queue_cwr(tp); + tcp_ecn_queue_cwr(tp); } static void tcp_cwnd_reduction(struct sock *sk, const int prior_unsacked, @@ -3453,7 +3456,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una, &sack_rtt_us); - if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) { + if (tcp_ecn_rcv_ecn_echo(tp, tcp_hdr(skb))) { flag |= FLAG_ECE; ack_ev_flags |= CA_ACK_ECE; } @@ -4193,7 +4196,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb) struct sk_buff *skb1; u32 seq, end_seq; - TCP_ECN_check_ce(tp, skb); + tcp_ecn_check_ce(tp, skb); if (unlikely(tcp_try_rmem_schedule(sk, skb, skb->truesize))) { NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFODROP); @@ -4376,7 +4379,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) skb_dst_drop(skb); __skb_pull(skb, tcp_hdr(skb)->doff * 4); - TCP_ECN_accept_cwr(tp, skb); + tcp_ecn_accept_cwr(tp, skb); tp->rx_opt.dsack = 0; @@ -5457,7 +5460,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, * state to ESTABLISHED..." */ - TCP_ECN_rcv_synack(tp, th); + tcp_ecn_rcv_synack(tp, th); tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); tcp_ack(sk, skb, FLAG_SLOWPATH); @@ -5576,7 +5579,7 @@ discard: tp->snd_wl1 = TCP_SKB_CB(skb)->seq; tp->max_window = tp->snd_wnd; - TCP_ECN_rcv_syn(tp, th); + tcp_ecn_rcv_syn(tp, th); tcp_mtup_init(sk); tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 47b73506b77..63d2680b65d 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -393,8 +393,8 @@ void tcp_openreq_init_rwin(struct request_sock *req, } EXPORT_SYMBOL(tcp_openreq_init_rwin); -static inline void TCP_ECN_openreq_child(struct tcp_sock *tp, - struct request_sock *req) +static void tcp_ecn_openreq_child(struct tcp_sock *tp, + const struct request_sock *req) { tp->ecn_flags = inet_rsk(req)->ecn_ok ? TCP_ECN_OK : 0; } @@ -507,7 +507,7 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req, if (skb->len >= TCP_MSS_DEFAULT + newtp->tcp_header_len) newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len; newtp->rx_opt.mss_clamp = req->mss; - TCP_ECN_openreq_child(newtp, req); + tcp_ecn_openreq_child(newtp, req); newtp->fastopen_rsk = NULL; newtp->syn_data_acked = 0; diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 86a0216fcaa..ee567e9e98c 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -318,7 +318,7 @@ static u16 tcp_select_window(struct sock *sk) } /* Packet ECN state for a SYN-ACK */ -static inline void TCP_ECN_send_synack(struct sock *sk, struct sk_buff *skb) +static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb) { const struct tcp_sock *tp = tcp_sk(sk); @@ -330,7 +330,7 @@ static inline void TCP_ECN_send_synack(struct sock *sk, struct sk_buff *skb) } /* Packet ECN state for a SYN. */ -static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb) +static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb) { struct tcp_sock *tp = tcp_sk(sk); @@ -344,8 +344,8 @@ static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb) } } -static __inline__ void -TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th, +static void +tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th, struct sock *sk) { if (inet_rsk(req)->ecn_ok) { @@ -358,7 +358,7 @@ TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th, /* Set up ECN state for a packet on a ESTABLISHED socket that is about to * be sent. */ -static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb, +static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb, int tcp_header_len) { struct tcp_sock *tp = tcp_sk(sk); @@ -960,7 +960,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, tcp_options_write((__be32 *)(th + 1), tp, &opts); if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0)) - TCP_ECN_send(sk, skb, tcp_header_size); + tcp_ecn_send(sk, skb, tcp_header_size); #ifdef CONFIG_TCP_MD5SIG /* Calculate the MD5 hash, as we have all we need now */ @@ -2800,7 +2800,7 @@ int tcp_send_synack(struct sock *sk) } TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK; - TCP_ECN_send_synack(sk, skb); + tcp_ecn_send_synack(sk, skb); } return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); } @@ -2859,7 +2859,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, memset(th, 0, sizeof(struct tcphdr)); th->syn = 1; th->ack = 1; - TCP_ECN_make_synack(req, th, sk); + tcp_ecn_make_synack(req, th, sk); th->source = htons(ireq->ir_num); th->dest = ireq->ir_rmt_port; /* Setting of flags are superfluous here for callers (and ECE is @@ -3098,7 +3098,7 @@ int tcp_connect(struct sock *sk) tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN); tp->retrans_stamp = tcp_time_stamp; tcp_connect_queue_skb(sk, buff); - TCP_ECN_send_syn(sk, buff); + tcp_ecn_send_syn(sk, buff); /* Send off SYN; include data in Fast Open. */ err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) : -- cgit v1.2.3-70-g09d2 From d0bf4a9e92b9a93ffeeacbd7b6cb83e0ee3dc2ef Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 29 Sep 2014 13:29:15 -0700 Subject: net: cleanup and document skb fclone layout Lets use a proper structure to clearly document and implement skb fast clones. Then, we might experiment more easily alternative layouts. This patch adds a new skb_fclone_busy() helper, used by tcp and xfrm, to stop leaking of implementation details. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/skbuff.h | 25 +++++++++++++++++++++++++ net/core/skbuff.c | 41 ++++++++++++++++++++--------------------- net/ipv4/tcp_output.c | 5 +---- net/xfrm/xfrm_policy.c | 4 +--- 4 files changed, 47 insertions(+), 28 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 262efdbc346..d8f7d74d5a4 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -781,6 +781,31 @@ struct sk_buff *alloc_skb_with_frags(unsigned long header_len, int *errcode, gfp_t gfp_mask); +/* Layout of fast clones : [skb1][skb2][fclone_ref] */ +struct sk_buff_fclones { + struct sk_buff skb1; + + struct sk_buff skb2; + + atomic_t fclone_ref; +}; + +/** + * skb_fclone_busy - check if fclone is busy + * @skb: buffer + * + * Returns true is skb is a fast clone, and its clone is not freed. + */ +static inline bool skb_fclone_busy(const struct sk_buff *skb) +{ + const struct sk_buff_fclones *fclones; + + fclones = container_of(skb, struct sk_buff_fclones, skb1); + + return skb->fclone == SKB_FCLONE_ORIG && + fclones->skb2.fclone == SKB_FCLONE_CLONE; +} + static inline struct sk_buff *alloc_skb_fclone(unsigned int size, gfp_t priority) { diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 4be570a4ab2..a8cebb40699 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -257,15 +257,16 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, kmemcheck_annotate_variable(shinfo->destructor_arg); if (flags & SKB_ALLOC_FCLONE) { - struct sk_buff *child = skb + 1; - atomic_t *fclone_ref = (atomic_t *) (child + 1); + struct sk_buff_fclones *fclones; - kmemcheck_annotate_bitfield(child, flags1); + fclones = container_of(skb, struct sk_buff_fclones, skb1); + + kmemcheck_annotate_bitfield(&fclones->skb2, flags1); skb->fclone = SKB_FCLONE_ORIG; - atomic_set(fclone_ref, 1); + atomic_set(&fclones->fclone_ref, 1); - child->fclone = SKB_FCLONE_UNAVAILABLE; - child->pfmemalloc = pfmemalloc; + fclones->skb2.fclone = SKB_FCLONE_UNAVAILABLE; + fclones->skb2.pfmemalloc = pfmemalloc; } out: return skb; @@ -524,8 +525,7 @@ static void skb_release_data(struct sk_buff *skb) */ static void kfree_skbmem(struct sk_buff *skb) { - struct sk_buff *other; - atomic_t *fclone_ref; + struct sk_buff_fclones *fclones; switch (skb->fclone) { case SKB_FCLONE_UNAVAILABLE: @@ -533,22 +533,21 @@ static void kfree_skbmem(struct sk_buff *skb) break; case SKB_FCLONE_ORIG: - fclone_ref = (atomic_t *) (skb + 2); - if (atomic_dec_and_test(fclone_ref)) - kmem_cache_free(skbuff_fclone_cache, skb); + fclones = container_of(skb, struct sk_buff_fclones, skb1); + if (atomic_dec_and_test(&fclones->fclone_ref)) + kmem_cache_free(skbuff_fclone_cache, fclones); break; case SKB_FCLONE_CLONE: - fclone_ref = (atomic_t *) (skb + 1); - other = skb - 1; + fclones = container_of(skb, struct sk_buff_fclones, skb2); /* The clone portion is available for * fast-cloning again. */ skb->fclone = SKB_FCLONE_UNAVAILABLE; - if (atomic_dec_and_test(fclone_ref)) - kmem_cache_free(skbuff_fclone_cache, other); + if (atomic_dec_and_test(&fclones->fclone_ref)) + kmem_cache_free(skbuff_fclone_cache, fclones); break; } } @@ -859,17 +858,18 @@ EXPORT_SYMBOL_GPL(skb_copy_ubufs); struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask) { - struct sk_buff *n; + struct sk_buff_fclones *fclones = container_of(skb, + struct sk_buff_fclones, + skb1); + struct sk_buff *n = &fclones->skb2; if (skb_orphan_frags(skb, gfp_mask)) return NULL; - n = skb + 1; if (skb->fclone == SKB_FCLONE_ORIG && n->fclone == SKB_FCLONE_UNAVAILABLE) { - atomic_t *fclone_ref = (atomic_t *) (n + 1); n->fclone = SKB_FCLONE_CLONE; - atomic_inc(fclone_ref); + atomic_inc(&fclones->fclone_ref); } else { if (skb_pfmemalloc(skb)) gfp_mask |= __GFP_MEMALLOC; @@ -3240,8 +3240,7 @@ void __init skb_init(void) SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache", - (2*sizeof(struct sk_buff)) + - sizeof(atomic_t), + sizeof(struct sk_buff_fclones), 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index ee567e9e98c..8d4eac79370 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2110,10 +2110,7 @@ bool tcp_schedule_loss_probe(struct sock *sk) static bool skb_still_in_host_queue(const struct sock *sk, const struct sk_buff *skb) { - const struct sk_buff *fclone = skb + 1; - - if (unlikely(skb->fclone == SKB_FCLONE_ORIG && - fclone->fclone == SKB_FCLONE_CLONE)) { + if (unlikely(skb_fclone_busy(skb))) { NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES); return true; diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index f623dca6ce3..4c4e457e788 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -1961,10 +1961,8 @@ static int xdst_queue_output(struct sock *sk, struct sk_buff *skb) struct xfrm_dst *xdst = (struct xfrm_dst *) dst; struct xfrm_policy *pol = xdst->pols[0]; struct xfrm_policy_queue *pq = &pol->polq; - const struct sk_buff *fclone = skb + 1; - if (unlikely(skb->fclone == SKB_FCLONE_ORIG && - fclone->fclone == SKB_FCLONE_CLONE)) { + if (unlikely(skb_fclone_busy(skb))) { kfree_skb(skb); return 0; } -- cgit v1.2.3-70-g09d2 From b2532eb9abd88384aa586169b54a3e53574f29f8 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 10 Oct 2014 18:06:35 -0700 Subject: tcp: fix ooo_okay setting vs Small Queues TCP Small Queues (tcp_tsq_handler()) can hold one reference on sk->sk_wmem_alloc, preventing skb->ooo_okay being set. We should relax test done to set skb->ooo_okay to take care of this extra reference. Minimal truesize of skb containing one byte of payload is SKB_TRUESIZE(1) Without this fix, we have more chance locking flows into the wrong transmit queue. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 8d4eac79370..0a5d97c20aa 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -914,9 +914,13 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, tcp_ca_event(sk, CA_EVENT_TX_START); /* if no packet is in qdisc/device queue, then allow XPS to select - * another queue. + * another queue. We can be called from tcp_tsq_handler() + * which holds one reference to sk_wmem_alloc. + * + * TODO: Ideally, in-flight pure ACK packets should not matter here. + * One way to get this would be to set skb->truesize = 2 on them. */ - skb->ooo_okay = sk_wmem_alloc_get(sk) == 0; + skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1); skb_push(skb, tcp_header_size); skb_reset_transport_header(skb); -- cgit v1.2.3-70-g09d2 From 9b462d02d6dd671a9ebdc45caed6fe98a53c0ebe Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 13 Oct 2014 06:27:47 -0700 Subject: tcp: TCP Small Queues and strange attractors TCP Small queues tries to keep number of packets in qdisc as small as possible, and depends on a tasklet to feed following packets at TX completion time. Choice of tasklet was driven by latencies requirements. Then, TCP stack tries to avoid reorders, by locking flows with outstanding packets in qdisc in a given TX queue. What can happen is that many flows get attracted by a low performing TX queue, and cpu servicing TX completion has to feed packets for all of them, making this cpu 100% busy in softirq mode. This became particularly visible with latest skb->xmit_more support Strategy adopted in this patch is to detect when tcp_wfree() is called from ksoftirqd and let the outstanding queue for this flow being drained before feeding additional packets, so that skb->ooo_okay can be set to allow select_queue() to select the optimal queue : Incoming ACKS are normally handled by different cpus, so this patch gives more chance for these cpus to take over the burden of feeding qdisc with future packets. Tested: lpaa23:~# ./super_netperf 1400 --google-pacing-rate 3028000 -H lpaa24 -l 3600 & lpaa23:~# sar -n DEV 1 10 | grep eth1 06:16:18 AM eth1 595448.00 1190564.00 38381.09 1760253.12 0.00 0.00 1.00 06:16:19 AM eth1 594858.00 1189686.00 38340.76 1758952.72 0.00 0.00 0.00 06:16:20 AM eth1 597017.00 1194019.00 38480.79 1765370.29 0.00 0.00 1.00 06:16:21 AM eth1 595450.00 1190936.00 38380.19 1760805.05 0.00 0.00 0.00 06:16:22 AM eth1 596385.00 1193096.00 38442.56 1763976.29 0.00 0.00 1.00 06:16:23 AM eth1 598155.00 1195978.00 38552.97 1768264.60 0.00 0.00 0.00 06:16:24 AM eth1 594405.00 1188643.00 38312.57 1757414.89 0.00 0.00 1.00 06:16:25 AM eth1 593366.00 1187154.00 38252.16 1755195.83 0.00 0.00 0.00 06:16:26 AM eth1 593188.00 1186118.00 38232.88 1753682.57 0.00 0.00 1.00 06:16:27 AM eth1 596301.00 1192241.00 38440.94 1762733.09 0.00 0.00 0.00 Average: eth1 595457.30 1190843.50 38381.69 1760664.84 0.00 0.00 0.50 lpaa23:~# ./tc -s -d qd sh dev eth1 | grep backlog backlog 7606336b 2513p requeues 167982 backlog 224072b 74p requeues 566 backlog 581376b 192p requeues 5598 backlog 181680b 60p requeues 1070 backlog 5305056b 1753p requeues 110166 // Here, this TX queue is attracting flows backlog 157456b 52p requeues 1758 backlog 672216b 222p requeues 3025 backlog 60560b 20p requeues 24541 backlog 448144b 148p requeues 21258 lpaa23:~# echo 1 >/proc/sys/net/ipv4/tcp_tsq_enable_tcp_wfree_ksoftirqd_detect Immediate jump to full bandwidth, and traffic is properly shard on all tx queues. lpaa23:~# sar -n DEV 1 10 | grep eth1 06:16:46 AM eth1 1397632.00 2795397.00 90081.87 4133031.26 0.00 0.00 1.00 06:16:47 AM eth1 1396874.00 2793614.00 90032.99 4130385.46 0.00 0.00 0.00 06:16:48 AM eth1 1395842.00 2791600.00 89966.46 4127409.67 0.00 0.00 1.00 06:16:49 AM eth1 1395528.00 2791017.00 89946.17 4126551.24 0.00 0.00 0.00 06:16:50 AM eth1 1397891.00 2795716.00 90098.74 4133497.39 0.00 0.00 1.00 06:16:51 AM eth1 1394951.00 2789984.00 89908.96 4125022.51 0.00 0.00 0.00 06:16:52 AM eth1 1394608.00 2789190.00 89886.90 4123851.36 0.00 0.00 1.00 06:16:53 AM eth1 1395314.00 2790653.00 89934.33 4125983.09 0.00 0.00 0.00 06:16:54 AM eth1 1396115.00 2792276.00 89984.25 4128411.21 0.00 0.00 1.00 06:16:55 AM eth1 1396829.00 2793523.00 90030.19 4130250.28 0.00 0.00 0.00 Average: eth1 1396158.40 2792297.00 89987.09 4128439.35 0.00 0.00 0.50 lpaa23:~# tc -s -d qd sh dev eth1 | grep backlog backlog 7900052b 2609p requeues 173287 backlog 878120b 290p requeues 589 backlog 1068884b 354p requeues 5621 backlog 996212b 329p requeues 1088 backlog 984100b 325p requeues 115316 backlog 956848b 316p requeues 1781 backlog 1080996b 357p requeues 3047 backlog 975016b 322p requeues 24571 backlog 990156b 327p requeues 21274 (All 8 TX queues get a fair share of the traffic) Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 0a5d97c20aa..e13d7785722 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -839,26 +839,38 @@ void tcp_wfree(struct sk_buff *skb) { struct sock *sk = skb->sk; struct tcp_sock *tp = tcp_sk(sk); + int wmem; + + /* Keep one reference on sk_wmem_alloc. + * Will be released by sk_free() from here or tcp_tasklet_func() + */ + wmem = atomic_sub_return(skb->truesize - 1, &sk->sk_wmem_alloc); + + /* If this softirq is serviced by ksoftirqd, we are likely under stress. + * Wait until our queues (qdisc + devices) are drained. + * This gives : + * - less callbacks to tcp_write_xmit(), reducing stress (batches) + * - chance for incoming ACK (processed by another cpu maybe) + * to migrate this flow (skb->ooo_okay will be eventually set) + */ + if (wmem >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current) + goto out; if (test_and_clear_bit(TSQ_THROTTLED, &tp->tsq_flags) && !test_and_set_bit(TSQ_QUEUED, &tp->tsq_flags)) { unsigned long flags; struct tsq_tasklet *tsq; - /* Keep a ref on socket. - * This last ref will be released in tcp_tasklet_func() - */ - atomic_sub(skb->truesize - 1, &sk->sk_wmem_alloc); - /* queue this socket to tasklet queue */ local_irq_save(flags); tsq = &__get_cpu_var(tsq_tasklet); list_add(&tp->tsq_node, &tsq->head); tasklet_schedule(&tsq->tasklet); local_irq_restore(flags); - } else { - sock_wfree(skb); + return; } +out: + sk_free(sk); } /* This routine actually transmits TCP packets queued in by -- cgit v1.2.3-70-g09d2 From 39bb5e62867de82b269b07df900165029b928359 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 30 Oct 2014 10:32:34 -0700 Subject: net: skb_fclone_busy() needs to detect orphaned skb Some drivers are unable to perform TX completions in a bound time. They instead call skb_orphan() Problem is skb_fclone_busy() has to detect this case, otherwise we block TCP retransmits and can freeze unlucky tcp sessions on mostly idle hosts. Signed-off-by: Eric Dumazet Fixes: 1f3279ae0c13 ("tcp: avoid retransmits of TCP packets hanging in host queues") Signed-off-by: David S. Miller --- include/linux/skbuff.h | 8 ++++++-- net/ipv4/tcp_output.c | 2 +- net/xfrm/xfrm_policy.c | 2 +- 3 files changed, 8 insertions(+), 4 deletions(-) (limited to 'net/ipv4/tcp_output.c') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 5884f95ff0e..6c8b6f604e7 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -799,15 +799,19 @@ struct sk_buff_fclones { * @skb: buffer * * Returns true is skb is a fast clone, and its clone is not freed. + * Some drivers call skb_orphan() in their ndo_start_xmit(), + * so we also check that this didnt happen. */ -static inline bool skb_fclone_busy(const struct sk_buff *skb) +static inline bool skb_fclone_busy(const struct sock *sk, + const struct sk_buff *skb) { const struct sk_buff_fclones *fclones; fclones = container_of(skb, struct sk_buff_fclones, skb1); return skb->fclone == SKB_FCLONE_ORIG && - fclones->skb2.fclone == SKB_FCLONE_CLONE; + fclones->skb2.fclone == SKB_FCLONE_CLONE && + fclones->skb2.sk == sk; } static inline struct sk_buff *alloc_skb_fclone(unsigned int size, diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 3af21296d96..a3d453b9474 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2126,7 +2126,7 @@ bool tcp_schedule_loss_probe(struct sock *sk) static bool skb_still_in_host_queue(const struct sock *sk, const struct sk_buff *skb) { - if (unlikely(skb_fclone_busy(skb))) { + if (unlikely(skb_fclone_busy(sk, skb))) { NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES); return true; diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index 4c4e457e788..88bf289abdc 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -1962,7 +1962,7 @@ static int xdst_queue_output(struct sock *sk, struct sk_buff *skb) struct xfrm_policy *pol = xdst->pols[0]; struct xfrm_policy_queue *pq = &pol->polq; - if (unlikely(skb_fclone_busy(skb))) { + if (unlikely(skb_fclone_busy(sk, skb))) { kfree_skb(skb); return 0; } -- cgit v1.2.3-70-g09d2