Messages in this thread | | | Subject | Re: [Patch 1/3] prefetch the mmap_sem in the fault path | From | Arjan van de Ven <> | Date | Thu, 23 Feb 2006 13:39:16 +0100 |
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On Thu, 2006-02-23 at 07:29 -0500, Jes Sorensen wrote: > >>>>> "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 ;(
most of it was done on a 2 way, but some tests were done on a 4-way. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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