diff options
| author | Eric Dumazet <eric.dumazet@gmail.com> | 2011-11-15 04:12:55 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2011-11-16 17:30:06 -0500 |
| commit | 588f033075d8c7efe28695402114eab3f9da47c4 (patch) | |
| tree | e057253b48041762ca0d747374521e5edf51c644 /net/core | |
| parent | 66846048f55c6c05a4c46c2daabb773173f8f28d (diff) | |
net: use jump_label for netstamp_needed
netstamp_needed seems a good candidate to jump_label conversion.
This avoids 3 conditional branches per incoming packet in fast path.
No measurable difference, given that these conditional branches are
predicted on modern cpus. Only a small icache reduction, thanks to the
unlikely() stuff.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/dev.c | 32 |
1 files changed, 14 insertions, 18 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index 6ba50a1e404..51f89cd0a3f 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -137,6 +137,7 @@ #include <linux/if_pppox.h> #include <linux/ppp_defs.h> #include <linux/net_tstamp.h> +#include <linux/jump_label.h> #include "net-sysfs.h" @@ -1449,34 +1450,32 @@ int call_netdevice_notifiers(unsigned long val, struct net_device *dev) } EXPORT_SYMBOL(call_netdevice_notifiers); -/* When > 0 there are consumers of rx skb time stamps */ -static atomic_t netstamp_needed = ATOMIC_INIT(0); +static struct jump_label_key netstamp_needed __read_mostly; void net_enable_timestamp(void) { - atomic_inc(&netstamp_needed); + jump_label_inc(&netstamp_needed); } EXPORT_SYMBOL(net_enable_timestamp); void net_disable_timestamp(void) { - atomic_dec(&netstamp_needed); + jump_label_dec(&netstamp_needed); } EXPORT_SYMBOL(net_disable_timestamp); static inline void net_timestamp_set(struct sk_buff *skb) { - if (atomic_read(&netstamp_needed)) + skb->tstamp.tv64 = 0; + if (static_branch(&netstamp_needed)) __net_timestamp(skb); - else - skb->tstamp.tv64 = 0; } -static inline void net_timestamp_check(struct sk_buff *skb) -{ - if (!skb->tstamp.tv64 && atomic_read(&netstamp_needed)) - __net_timestamp(skb); -} +#define net_timestamp_check(COND, SKB) \ + if (static_branch(&netstamp_needed)) { \ + if ((COND) && !(SKB)->tstamp.tv64) \ + __net_timestamp(SKB); \ + } \ static int net_hwtstamp_validate(struct ifreq *ifr) { @@ -2997,8 +2996,7 @@ int netif_rx(struct sk_buff *skb) if (netpoll_rx(skb)) return NET_RX_DROP; - if (netdev_tstamp_prequeue) - net_timestamp_check(skb); + net_timestamp_check(netdev_tstamp_prequeue, skb); trace_netif_rx(skb); #ifdef CONFIG_RPS @@ -3230,8 +3228,7 @@ static int __netif_receive_skb(struct sk_buff *skb) int ret = NET_RX_DROP; __be16 type; - if (!netdev_tstamp_prequeue) - net_timestamp_check(skb); + net_timestamp_check(!netdev_tstamp_prequeue, skb); trace_netif_receive_skb(skb); @@ -3362,8 +3359,7 @@ out: */ int netif_receive_skb(struct sk_buff *skb) { - if (netdev_tstamp_prequeue) - net_timestamp_check(skb); + net_timestamp_check(netdev_tstamp_prequeue, skb); if (skb_defer_rx_timestamp(skb)) return NET_RX_SUCCESS; |