Re: [PATCH] improve __GFP_COLD/__GFP_ZERO interaction

["Jan Beulich" <JBeulich@suse.com>]

>>> On 02.06.14 at 17:16, <kirill@shutemov.name> wrote:
> On Mon, Jun 02, 2014 at 03:46:10PM +0100, Jan Beulich wrote:
>> For cold page allocations using the normal clear_highpage() mechanism
>> may be inefficient on certain architectures, namely due to needlessly
>> replacing a good part of the data cache contents. Introduce an arch-
>> overridable clear_cold_highpage() (using streaming non-temporal stores
>> on x86, where an override gets implemented right away) to make use of
>> in this specific case.
>> 
>> Leverage the impovement in the Xen balloon driver, eliminating the
>> explicit scrub_page() function.
> 
> Any benchmark data?
> 
> I've tried non-temporal stores to clear huge pages, but it didn't helped
> much. I believe it can vary between micro-architectures, but we need
> numbers. I've played with Westmere that time.

It's not at all clear to me what to measure here - after all this isn't
about improving the page clearing latency or throughput, but about
avoiding to disturb other operations.

Jan

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