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authorEric Dumazet <eric.dumazet@gmail.com>2010-10-15 07:44:11 +0200
committerDavid S. Miller <davem@davemloft.net>2010-10-20 12:02:23 +0200
commit27b75c95f10d249574d9c4cb9dab878107faede8 (patch)
tree466656d86aaa395951e12b50903e730203c5f86f /fs/xfs/xfs_iget.c
parentnet: allocate tx queues in register_netdevice (diff)
downloadlinux-27b75c95f10d249574d9c4cb9dab878107faede8.tar.xz
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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 'fs/xfs/xfs_iget.c')
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