linux-kernel - Re: [mm/hugetlb] c77c0a8ac4: will-it-scale.per_process

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Date:   Tue, 14 Jan 2020 09:57:14 -0500
From:   Waiman Long <longman@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>,
        kernel test robot <rong.a.chen@...el.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Davidlohr Bueso <dbueso@...e.de>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Matthew Wilcox <willy@...radead.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org
Subject: Re: [mm/hugetlb] c77c0a8ac4: will-it-scale.per_process_ops 15.9%
 improvement

On 1/14/20 4:12 AM, Michal Hocko wrote:
> On Tue 14-01-20 16:56:37, kernel test robot wrote:
>> Greeting,
>>
>> FYI, we noticed a 15.9% improvement of will-it-scale.per_process_ops due to commit:
>>
>>
>> commit: c77c0a8ac4c522638a8242fcb9de9496e3cdbb2d ("mm/hugetlb: defer freeing of huge pages if in non-task context")
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> This is more than surprising because the patch has only changed the
> behavior for hugetlb pages freed from the (soft)interrupt context and
> that should be a very rare event. Does the test really generate a lot of
> those?
>
Yes, I have the same question. I was not expecting to see any
performance impact.

Cheers,
Longman