linux-kernel - Re: [PATCH v4] mm/page_alloc: bail out on fatal signal during reclaim/compaction retry attempt

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Message-ID: <YLTJjJqemt5Uv9vP@dhcp22.suse.cz>
Date:   Mon, 31 May 2021 13:33:32 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Aaron Tomlin <atomlin@...hat.com>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org, vbabka@...e.cz,
        willy@...radead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] mm/page_alloc: bail out on fatal signal during
 reclaim/compaction retry attempt

On Thu 20-05-21 15:29:01, Aaron Tomlin wrote:
> A customer experienced a low-memory situation and decided to issue a
> SIGKILL (i.e. a fatal signal). Instead of promptly terminating as one
> would expect, the aforementioned task remained unresponsive.
> 
> Further investigation indicated that the task was "stuck" in the
> reclaim/compaction retry loop. Now, it does not make sense to retry
> compaction when a fatal signal is pending.

Is this really true in general? The memory reclaim is retried even when
fatal signals are pending. Why should be compaction different? I do
agree that retrying way too much is bad but is there any reason why this
special case doesn't follow the max retry logic?
-- 
Michal Hocko
SUSE Labs