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authorEric Dumazet <dada1@cosmosbay.com>2005-09-07 02:18:16 +0400
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-08 03:57:41 +0400
commit3f4bb1f4199b7dc0c958447b1e4898980013b884 (patch)
tree3d8aacfc6b7bbf7b2d224ae10ca693c55c64739e /fs/buffer.c
parent0811bab24ff1eecab38110eda7ea7847db95c64e (diff)
downloadlinux-3f4bb1f4199b7dc0c958447b1e4898980013b884.tar.xz
[PATCH] struct dentry: place d_hash close to d_parent and d_name to speedup lookups
dentry cache uses sophisticated RCU technology (and prefetching if available) but touches 2 cache lines per dentry during hlist lookup. This patch moves d_hash in the same cache line than d_parent and d_name fields so that : 1) One cache line is needed instead of two. 2) the hlist_for_each_rcu() prefetching has a chance to bring all the needed data in advance, not only the part that includes d_hash.next. I also changed one old comment that was wrong for 64bits. A further optimisation would be to separate dentry in two parts, one that is mostly read, and one writen (d_count/d_lock) to avoid false sharing on SMP/NUMA but this would need different field placement depending on 32bits or 64bits platform. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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