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References: <20210818152457.35846-1-hannes@cmpxchg.org>
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From:   Shakeel Butt <shakeelb@google.com>
Date:   Thu, 19 Aug 2021 08:04:19 -0700
Message-ID: <CALvZod5y4WquXhH6BdVAyqMNqxCm=RGkOk-iBkRuW0uQPCz_1g@mail.gmail.com>
Subject: Re: [PATCH] mm: vmscan: fix missing psi annotation for node_reclaim()
To:     Johannes Weiner <hannes@cmpxchg.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Rik van Riel <riel@surriel.com>,
        Linux MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Kernel Team <kernel-team@fb.com>
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On Wed, Aug 18, 2021 at 8:26 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> In a debugging session the other day, Rik noticed that node_reclaim()
> was missing memstall annotations. This means we'll miss pressure and
> lost productivity resulting from reclaim on an overloaded local NUMA
> node when vm.zone_reclaim_mode is enabled.
>
> There haven't been any reports, but that's likely because
> vm.zone_reclaim_mode hasn't been a commonly used feature recently, and
> the intersection between such setups and psi users is probably
> nil. Although, secondary memory such as CXL-connected DIMMS,
> persistent memory etc. and the page demotion patches that handle them
> (https://lore.kernel.org/lkml/20210401183216.443C4443@viggo.jf.intel.com/)
> could soon make this a more common codepath again.
>
> Reported-by: Rik van Riel <riel@surriel.com>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Reviewed-by: Shakeel Butt <shakeelb@google.com>