linux-kernel - Re: [PATCH 2/3] mm/util.c: make vm_memory

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Message-ID: <20200515090440.GN29153@dhcp22.suse.cz>
Date:   Fri, 15 May 2020 11:04:40 +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>,
        "Kleen, Andi" <andi.kleen@...el.com>,
        "Chen, Tim C" <tim.c.chen@...el.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] mm/util.c: make vm_memory_committed() more accurate

On Fri 15-05-20 16:11:09, Feng Tang wrote:
> On Fri, May 15, 2020 at 03:23:07PM +0800, Michal Hocko wrote:
> > On Fri 08-05-20 15:25:16, Feng Tang wrote:
> > > percpu_counter_sum_positive() will provide more accurate info.
> > 
> > Why do we need that?
> 
> This is a preparation for patch 3/3, which will enlarge the batch size
> of percpu-counter 'vm_committed_as'. Andi Kleen concerned that may
> hurt the accuracy for those readers (currently only /proc/meminfo
> and hyperV balloon drivers for status check)
> 
> As in worst case, the deviation could be 'batch * nr_cpus', and
> with patch 3/3, that could be totalram_pages/16.

This information belongs to the changelog.
-- 
Michal Hocko
SUSE Labs