linux-kernel - Re: [PATCH v1] tools/cgroup: introduce cgroup v2 memory.events listener

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Message-Id: <20231106140934.3f5d4960141562fe8da53906@linux-foundation.org>
Date:   Mon, 6 Nov 2023 14:09:34 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Dmitry Rokosov <ddrokosov@...utedevices.com>
Cc:     <hannes@...xchg.org>, <mhocko@...nel.org>,
        <roman.gushchin@...ux.dev>, <shakeelb@...gle.com>,
        <muchun.song@...ux.dev>, <kernel@...rdevices.ru>,
        <rockosov@...il.com>, <cgroups@...r.kernel.org>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <bpf@...r.kernel.org>
Subject: Re: [PATCH v1] tools/cgroup: introduce cgroup v2 memory.events
 listener

On Fri, 13 Oct 2023 21:41:07 +0300 Dmitry Rokosov <ddrokosov@...utedevices.com> wrote:

> This is a simple listener for memory events that handles counter
> changes in runtime. It can be set up for a specific memory cgroup v2.
> 
> The output example:
> =====
> $ /tmp/cgroup_v2_event_listener test
> Initialized MEMCG events with counters:
> MEMCG events:
> 	low: 0
> 	high: 0
> 	max: 0
> 	oom: 0
> 	oom_kill: 0
> 	oom_group_kill: 0
> Started monitoring memory events from '/sys/fs/cgroup/test/memory.events'...
> Received event in /sys/fs/cgroup/test/memory.events:
> *** 1 MEMCG oom_kill event, change counter 0 => 1
> Received event in /sys/fs/cgroup/test/memory.events:
> *** 1 MEMCG oom_kill event, change counter 1 => 2
> Received event in /sys/fs/cgroup/test/memory.events:
> *** 1 MEMCG oom_kill event, change counter 2 => 3
> Received event in /sys/fs/cgroup/test/memory.events:
> *** 1 MEMCG oom_kill event, change counter 3 => 4
> Received event in /sys/fs/cgroup/test/memory.events:
> *** 2 MEMCG max events, change counter 0 => 2
> Received event in /sys/fs/cgroup/test/memory.events:
> *** 8 MEMCG max events, change counter 2 => 10
>
> ...
>

Looks nice to me.

Perhaps it should be under ./samples/?

I suggest adding a comment to __memory_events_show() reminding people
to update this code if new events are added.