linux-kernel - Re: [PATCH] mm/oom_kill: revert watchdog reset in global OOM process

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Message-ID: <Z6yM1dycm5E7vfT0@tiehlicka>
Date: Wed, 12 Feb 2025 12:58:13 +0100
From: Michal Hocko <mhocko@...e.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Chen Ridong <chenridong@...weicloud.com>, akpm@...ux-foundation.org,
	hannes@...xchg.org, yosryahmed@...gle.com, roman.gushchin@...ux.dev,
	shakeel.butt@...ux.dev, muchun.song@...ux.dev, davidf@...eo.com,
	mkoutny@...e.com, paulmck@...nel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	chenridong@...wei.com, wangweiyang2@...wei.com
Subject: Re: [PATCH] mm/oom_kill: revert watchdog reset in global OOM process

On Wed 12-02-25 10:34:06, Vlastimil Babka wrote:
> On 2/12/25 10:19, Chen Ridong wrote:
> > 
> > 
> > On 2025/2/12 16:57, Michal Hocko wrote:
> >> On Wed 12-02-25 02:57:07, Chen Ridong wrote:
> >>> From: Chen Ridong <chenridong@...wei.com>
> >>>
> >>> Unlike memcg OOM, which is relatively common, global OOM events are rare
> >>> and typically indicate that the entire system is under severe memory
> >>> pressure. The commit ade81479c7dd ("memcg: fix soft lockup in the OOM
> >>> process") added the touch_softlockup_watchdog in the global OOM handler to
> >>> suppess the soft lockup issues. However, while this change can suppress
> >>> soft lockup warnings, it does not address RCU stalls, which can still be
> >>> detected and may cause unnecessary disturbances. Simply remove the
> >>> modification from the global OOM handler.
> >>>
> >>> Fixes: ade81479c7dd ("memcg: fix soft lockup in the OOM process")
> >> 
> >> But this is not really fixing anything, is it? While this doesn't
> >> address a potential RCU stall it doesn't address any actual problem.
> >> So why do we want to do this?
> >> 
> > 
> > 
> > [1]
> > https://lore.kernel.org/cgroups/0d9ea655-5c1a-4ba9-9eeb-b45d74cc68d0@huaweicloud.com/
> > 
> > As previously discussed, the work I have done on the global OOM is 'half
> > of the job'. Based on our discussions, I thought that it would be best
> > to abandon this approach for global OOM. Therefore, I am sending this
> > patch to revert the changes.
> > 
> > Or just leave it?
> 
> I suggested that part doesn't need to be in the patch, but if it was merged
> with it, we can just leave it there. Thanks.

Agreed!

-- 
Michal Hocko
SUSE Labs