linux-kernel - Re: [PATCH] mm: introduce oom_kill

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Message-ID: <20201109073706.GA12240@dhcp22.suse.cz>
Date:   Mon, 9 Nov 2020 08:37:06 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: introduce oom_kill_disable sysctl knob

On Fri 06-11-20 12:32:38, Minchan Kim wrote:
> It's hard to have some tests to be supposed to work under heavy
> memory pressure(e.g., injecting some memory hogger) because
> out-of-memory killer easily kicks out one of processes so system
> is broken or system loses the memory pressure state since it has
> plenty of free memory soon so.

I do not follow the reasoning here. So you want to test for a close to
no memory available situation and the oom killer stands in the way
because it puts a relief?

> Even though we could mark existing process's oom_adj to -1000,
> it couldn't cover upcoming processes to be forked for the job.

Why?

> This knob is handy to keep system memory pressure.

This sounds like a very dubious reason to introduce a knob to cripple
the system.

I can see some reason to control the oom handling policy because the
effect of the oom killer is really disruptive but a global on/off switch
sounds like a too coarse interface. Really what kind of production
environment would ever go with oom killer disabled completely?

-- 
Michal Hocko
SUSE Labs