linux-kernel - Re: [PATCH memcg 0/1] false global OOM triggered by memcg-limited task

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Message-ID: <YW6GoZhFUJc1uLYr@dhcp22.suse.cz>
Date:   Tue, 19 Oct 2021 10:49:37 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Vasily Averin <vvs@...tuozzo.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>,
        Uladzislau Rezki <urezki@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Shakeel Butt <shakeelb@...gle.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel@...nvz.org
Subject: Re: [PATCH memcg 0/1] false global OOM triggered by memcg-limited
 task

On Tue 19-10-21 09:30:18, Vasily Averin wrote:
[...]
> With my patch ("memcg: prohibit unconditional exceeding the limit of dying tasks") try_charge_memcg() can fail:
> a) due to fatal signal
> b) when mem_cgroup_oom -> mem_cgroup_out_of_memory -> out_of_memory() returns false (when select_bad_process() found nothing)
> 
> To handle a) we can follow to your suggestion and skip excution of out_of_memory() in pagefault_out_of memory()
> To handle b) we can go to retry: if mem_cgroup_oom() return OOM_FAILED.

How is b) possible without current being killed? Do we allow remote
charging?

> However all these cases can be successfully handled by my new patch
> "memcg: prevent false global OOM triggered by memcg limited task"
> and I think it is better solution.

I have already replied to your approach in other email. Sorry our
replies have crossed.
-- 
Michal Hocko
SUSE Labs