tree d222fb0e1c522d4bd506cb8c24c498a7e1589da2
parent 4bc32c4d5cde5c57edcc9c2fe5057da8a4dd0153
author Arjan van de Ven <arjan@intel.linux.com> 1143300610 +0100
committer Linus Torvalds <torvalds@g5.osdl.org> 1143306654 -0800

[PATCH] x86_64: prefetch the mmap_sem in the fault path

In a micro-benchmark that stresses the pagefault path, the down_read_trylock
on the mmap_sem showed up quite high on the profile. Turns out this lock is
bouncing between cpus quite a bit and thus is cache-cold a lot. This patch
prefetches the lock (for write) as early as possible (and before some other
somewhat expensive operations). With this patch, the down_read_trylock
basically fell out of the top of profile.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>