linux-kernel - Re: [PATCH -next] memcg: don't handle event

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Message-ID: <ZkOBaNffNi4rmR8h@P9FQF9L96D>
Date: Tue, 14 May 2024 08:21:12 -0700
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: Michal Hocko <mhocko@...e.com>
Cc: Xiu Jianfeng <xiujianfeng@...wei.com>, hannes@...xchg.org,
	shakeel.butt@...ux.dev, muchun.song@...ux.dev,
	akpm@...ux-foundation.org, cgroups@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] memcg: don't handle event_list for v2 when
 offlining

On Tue, May 14, 2024 at 04:09:58PM +0200, Michal Hocko wrote:
> On Tue 14-05-24 13:11:06, Xiu Jianfeng wrote:
> > The event_list for memcg is only valid for v1 and not used for v2,
> > so it's unnessesary to handle event_list for v2.
> 
> You are right but the code as is works just fine. The list will be
> empty. It is true that we do not need to take event_list_lock lock but
> nobody should be using this lock anyway. Also the offline callback is
> not particularly hot path. So why do we want to change the code?

+1 to that.

Plus this code will be moved to a separate function in mm/memcontrol-v1.c
and luckily can be compiled out entirely for users who don't need the
cgroup v1 support.

Thanks!