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authorEric Dumazet <dada1@cosmosbay.com>2007-02-10 01:44:48 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-02-11 10:51:25 -0800
commit4ba4d4c0c52201009232fe9e781a281054a24e75 (patch)
tree4b4d47c78c561fc8f3d79713e7f80def3d9b73ce /fs
parent0aa5de8590d684274f57647a870851f101bb3543 (diff)
[PATCH] struct vfsmount: keep mnt_count & mnt_expiry_mark away from mnt_flags
I noticed cache misses in touch_atime() that can be avoided if we keep mnt_count & mnt_expiry_mark in a different cache line than mnt_flags (mostly read) mnt_count & mnt_expiry_mark are modified each time a file is opened/closed in a file system. touch_atime() is called each time a file is read, and generally needs to read mnt_flags. Other fields of struct vfsmount are mostly read so I chose to move mnt_count & mnt_expiry_mark at the end of struct vfsmount. And adding a comment so that nobody tries to re-arrange fields to fill the holes :) On 64bits platforms, the new offsetof(mnt_count) is 0xC0 On 32bits platforms, it is 0x60, so I didnot add a ____cacheline_aligned_in_smp because it would have a too big impact on the size of this object (in particular if CONFIG_X86_L1_CACHE_SHIFT=7) Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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