Messages in this thread | | | Subject | Re: [Patch 1/3] prefetch the mmap_sem in the fault path | From | Jes Sorensen <> | Date | 23 Feb 2006 07:29:00 -0500 |
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>>>>> "Arjan" == Arjan van de Ven <arjan@intel.linux.com> writes:
Arjan> In a micro-benchmark that stresses the pagefault path, the Arjan> down_read_trylock on the mmap_sem showed up quite high on the Arjan> profile. Turns out this lock is bouncing between cpus quite a Arjan> bit and thus is cache-cold a lot. This patch prefetches the Arjan> lock (for write) as early as possible (and before some other Arjan> somewhat expensive operations). With this patch, the Arjan> down_read_trylock basically fell out of the top of profile.
Out of curiousity, how big was the box used for testing? It might be worth investigating if anything can be done to reduce the number of times that lock is taken in the first place.
After all, what's a pain on a 4-way tends to be an utter nightmare on a 16-way ;(
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