linux-kernel - Re: [PATCH 0/3] make vm_committed_as_batch aware of vm overcommit policy

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Message-ID: <20200528154809.GH27484@dhcp22.suse.cz>
Date:   Thu, 28 May 2020 17:48:09 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Feng Tang <feng.tang@...el.com>
Cc:     Qian Cai <cai@....pw>, Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Matthew Wilcox <willy@...radead.org>,
        Mel Gorman <mgorman@...e.de>,
        Kees Cook <keescook@...omium.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Iurii Zaikin <yzaikin@...gle.com>, andi.kleen@...el.com,
        tim.c.chen@...el.com, dave.hansen@...el.com, ying.huang@...el.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] make vm_committed_as_batch aware of vm overcommit
 policy

On Thu 28-05-20 23:10:20, Feng Tang wrote:
[...]
> If it's true, then there could be 2 solutions, one is to
> skip the WARN_ONCE as it has no practical value, as the real
> check is the following code, the other is to rectify the
> percpu counter when the policy is changing to OVERCOMMIT_NEVER. 

I would simply drop the WARN_ONCE. Looking at the history this has been
added by 82f71ae4a2b8 ("mm: catch memory commitment underflow") to have
a safety check for issues which have been fixed. There doesn't seem to
be any bug reports mentioning this splat since then so it is likely just
spending cycles for a hot path (yes many people run with DEBUG_VM)
without a strong reason.
-- 
Michal Hocko
SUSE Labs