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SubjectRe: [PATCH, RFC 0/6] Avoid cache trashing on clearing huge/gigantic page
On Mon, Jul 23, 2012 at 04:30:20PM -0700, Andrew Morton wrote:
> On Fri, 20 Jul 2012 15:50:16 +0300
> "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> 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.
> >
> > It would be nice to test the patchset with more workloads. Especially if
> > you see performance regression with THP.
> >
> > Any feedback is appreciated.
>
> This all looks pretty sane to me. Some detail-poking from the x86 guys
> would be nice.
>
> What do other architectures need to do? Simply implement
> clear_page_nocache()?

And define ARCH_HAS_USER_NOCACHE to 1.

> I believe that powerpc is one, not sure about
> others. Please update the changelogs to let arch maintainers know
> what they should do and cc those people on future versions?

Okay.

--
Kirill A. Shutemov
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