linux-kernel - Re: [NUMA Balancing] e39bb6be9f: will-it-scale.per_thread

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Message-ID: <CAHk-=wg+mJrTvun6qkdEnkZk9FSyj6vNYU2j7QY-iPn0g_y1nw@mail.gmail.com>
Date:   Fri, 1 Apr 2022 09:35:24 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     kernel test robot <oliver.sang@...el.com>
Cc:     Yang Shi <shy828301@...il.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>,
        Rik van Riel <riel@...riel.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Zi Yan <ziy@...dia.com>, Wei Xu <weixugc@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        zhongjiang-ali <zhongjiang-ali@...ux.alibaba.com>,
        Feng Tang <feng.tang@...el.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        kernel test robot <lkp@...el.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        fengwei.yin@...el.com
Subject: Re: [NUMA Balancing] e39bb6be9f: will-it-scale.per_thread_ops 64.4% improvement

On Fri, Apr 1, 2022 at 2:42 AM kernel test robot <oliver.sang@...el.com> wrote:
>
> FYI, we noticed a 64.4% improvement of will-it-scale.per_thread_ops due to commit:
> e39bb6be9f2b ("NUMA Balancing: add page promotion counter")

That looks odd and unlikely.

That commit only modifies some page counting statistics. Sure, it
could be another cache layout thing, and maybe it's due to the subtle
change in how NUMA_PAGE_MIGRATE gets counted, but it still looks a bit
odd.

               Linus