Re: [PATCH] perf: optimize clear page in Intel specified model with movq instruction

[Borislav Petkov]

On Thu, Sep 09, 2021 at 04:45:51PM +0800, Jinhua Wu wrote:
> Clear page is the most time-consuming procedure in page fault handling.
> Kernel use fast-string instruction to clear page. We found that in specified
> Intel model such as CPX and ICX, the movq instruction perform much better
> than fast-string instruction when corresponding page is not in cache.
> But when the page is in cache, fast string perform better. We show the test
> result in the following:

What you should do is show the extensive tests you've run with
real-world benchmarks where you really can show 40% performance
improvement.

Also, the static branch "approach" you're using ain't gonna happen. If
anything, another X86_FEATURE_* bit.

Good luck.

-- 
Regards/Gruss,
    Boris.

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