Re: [PATCH v4 0/8] Avoid cache trashing on clearing huge/giganticpage
From: Andrew Morton
Date: Thu Sep 13 2012 - 19:05:24 EST
On Mon, 20 Aug 2012 16:52:29 +0300
"Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
> Clearing a 2MB huge page will typically blow away several levels of CPU
> caches. To avoid this only cache clear the 4K area around the fault
> address and use a cache avoiding clears for the rest of the 2MB area.
> This patchset implements cache avoiding version of clear_page only for
> x86. If an architecture wants to provide cache avoiding version of
> clear_page it should to define ARCH_HAS_USER_NOCACHE to 1 and implement
> clear_page_nocache() and clear_user_highpage_nocache().
Patchset looks nice to me, but the changelogs are terribly short of
performance measurements. For this sort of change I do think it is
important that pretty exhaustive testing be performed, and that the
results (or a readable summary of them) be shown. And that testing
should be designed to probe for slowdowns, not just the speedups!
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/