linux-kernel - Re: [PATCH 3/3] mm: adjust vm_committed_as_batch according to vm overcommit policy

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Message-ID: <20200515074443.GI29153@dhcp22.suse.cz>
Date:   Fri, 15 May 2020 09:44:43 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Feng Tang <feng.tang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        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 3/3] mm: adjust vm_committed_as_batch according to vm
 overcommit policy

On Fri 08-05-20 15:25:17, Feng Tang wrote:
> When checking a performance change for will-it-scale scalability
> mmap test [1], we found very high lock contention for spinlock of
> percpu counter 'vm_committed_as':

Btw. you are focusing on a microbenchmark here but I believe that there
are non-synthetic worklaods which would benefit from a larger batch.
E.g. large in memory databases which do large mmaps during startups
from multiple threads.
-- 
Michal Hocko
SUSE Labs