Re: [PATCH, RFC 0/6] Avoid cache trashing on clearing huge/giganticpage

From: Andrew Morton
Date: Mon Jul 23 2012 - 19:30:21 EST

On Fri, 20 Jul 2012 15:50:16 +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.
> 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()? 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?

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