linux-kernel - Re: [PATCH] mm/memcontrol.c: drains percpu charge caches in memory.reclaim

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Message-ID: <20221110144243.GA10562@blackbody.suse.cz>
Date:   Thu, 10 Nov 2022 15:42:43 +0100
From:   Michal Koutný <mkoutny@...e.com>
To:     Lu Jialin <lujialin4@...wei.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <songmuchun@...edance.com>,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH] mm/memcontrol.c: drains percpu charge caches in
 memory.reclaim

Hello Jialin.

On Thu, Nov 10, 2022 at 02:53:16PM +0800, Lu Jialin <lujialin4@...wei.com> wrote:
> When user use memory.reclaim to reclaim memory, after drain percpu lru
> caches, drain percpu charge caches for given memcg stock in the hope
> of introducing more evictable pages.

Do you have any data on materialization of this hope?

IIUC, the stock is useful for batched accounting to page_counter but it
doesn't represent real pages. I.e. your change may reduce the
page_counter value but it would not release any pages. Or have I missed
a way how it helps with the reclaim?

Thanks,
Michal

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