linux-kernel - Re: [PATCH] /proc/PID/smaps: Add PMD migration entry parsing

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Message-ID: <20200402062717.GB22681@dhcp22.suse.cz>
Date:   Thu, 2 Apr 2020 08:27:17 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     "Huang, Ying" <ying.huang@...el.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Zi Yan <ziy@...dia.com>, Vlastimil Babka <vbabka@...e.cz>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Jérôme Glisse <jglisse@...hat.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>
Subject: Re: [PATCH] /proc/PID/smaps: Add PMD migration entry parsing

On Wed 01-04-20 16:04:32, Andrew Morton wrote:
> On Tue, 31 Mar 2020 16:56:04 +0800 "Huang, Ying" <ying.huang@...el.com> wrote:
> 
> > From: Huang Ying <ying.huang@...el.com>
> > 
> > Now, when read /proc/PID/smaps, the PMD migration entry in page table is simply
> > ignored.  To improve the accuracy of /proc/PID/smaps, its parsing and processing
> > is added.
> 
> It would be helpful to show the before-and-after output in the changelog.

Migration entries are ephemeral. Is this observable in practice? I
suspect this is just primarily motivated by reading the code more than
hitting the actual problem.
-- 
Michal Hocko
SUSE Labs