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authorEric Dumazet <eric.dumazet@gmail.com>2010-10-15 05:44:11 +0000
committerDavid S. Miller <davem@davemloft.net>2010-10-20 03:02:23 -0700
commit27b75c95f10d249574d9c4cb9dab878107faede8 (patch)
tree466656d86aaa395951e12b50903e730203c5f86f /include/linux/skbuff.h
parente6484930d7c73d324bccda7d43d131088da697b9 (diff)
net: avoid RCU for NOCACHE dst
There is no point using RCU for dst we allocate for a very short time (used once). Change dst_release() to take DST_NOCACHE into account, but also change skb_dst_set_noref() to force a refcount increment for such dst. This is a _huge_ gain, because we dont waste memory to store xx thousand of dsts. Instead of queueing them to RCU, we can free them instantly. CPU caches can stay hot, re-using same memory blocks to hold temporary dsts. Note : remove unneeded smp_mb__before_atomic_dec(); in dst_release(), since atomic_dec_return() implies a full memory barrier. Stress test, 160.000.000 udp frames sent, IP route cache disabled (DDOS). Before: real 0m38.091s user 0m13.189s sys 7m53.018s After: real 0m29.946s user 0m12.157s sys 7m40.605s For reference, if IP route cache was enabled : real 0m32.030s user 0m10.521s sys 8m15.243s Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/skbuff.h')
-rw-r--r--include/linux/skbuff.h14
1 files changed, 1 insertions, 13 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 05a358f1ba1..e6ba898de61 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -460,19 +460,7 @@ static inline void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst)
skb->_skb_refdst = (unsigned long)dst;
}
-/**
- * skb_dst_set_noref - sets skb dst, without a reference
- * @skb: buffer
- * @dst: dst entry
- *
- * Sets skb dst, assuming a reference was not taken on dst
- * skb_dst_drop() should not dst_release() this dst
- */
-static inline void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst)
-{
- WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());
- skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF;
-}
+extern void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst);
/**
* skb_dst_is_noref - Test if skb dst isnt refcounted