linux-kernel - Re: [PATCH resend] memcg: introduce per-memcg reclaim interface

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Message-ID: <20220405100906.GB13806@blackbody.suse.cz>
Date:   Tue, 5 Apr 2022 12:09:06 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Wei Xu <weixugc@...gle.com>, Johannes Weiner <hannes@...xchg.org>,
        Yosry Ahmed <yosryahmed@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Cgroups <cgroups@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Jonathan Corbet <corbet@....net>, Yu Zhao <yuzhao@...gle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Greg Thelen <gthelen@...gle.com>
Subject: Re: [PATCH resend] memcg: introduce per-memcg reclaim interface

On Mon, Apr 04, 2022 at 10:08:43AM -0700, Shakeel Butt <shakeelb@...gle.com> wrote:
> What would be the challenge on returning the number of bytes reclaimed
> through cgroup interface?

You'd need an object that represents the write size:

> bfd = open("/sys/kernel/mm/reclaim/balloon", O_RDWR);
> dprintf(bfd, "type=file nodemask=1-2 timeout=30\n")
> 
> fd = open("/sys/kernel/fs/cgroup/foo/memory.reclaim", O_WRONLY);
> reclaimed = splice(bfd, NULL, fd, NULL, reclaim_size);

(I'm joking with this API but it is a resembling concept.)

Michal