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

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Message-ID: <7dd7109d-7554-4b69-8a46-02620abb8583@huaweicloud.com>
Date: Wed, 12 Feb 2025 17:52:02 +0800
From: Chen Ridong <chenridong@...weicloud.com>
To: Vlastimil Babka <vbabka@...e.cz>, Michal Hocko <mhocko@...e.com>
Cc: 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 2025/2/12 17:34, 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.

See. Thank you very much.

Best regards,
Ridong