linux-kernel - Re: [PATCH] mm/vmstat: Fix placement of per-node stats in /proc/zoneinfo

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Message-ID: <32f8680b-ca66-4126-84ac-d8e375ce2f18@amd.com>
Date: Fri, 26 Jul 2024 09:46:26 +0530
From: "Garg, Shivank" <shivankg@....com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, vbabka@...e.cz,
 hillf.zj@...baba-inc.com, mgorman@...hsingularity.net, hannes@...xchg.org
Subject: Re: [PATCH] mm/vmstat: Fix placement of per-node stats in
 /proc/zoneinfo



On 7/26/2024 1:17 AM, Andrew Morton wrote:
> On Thu, 25 Jul 2024 16:26:26 +0530 Shivank Garg <shivankg@....com> wrote:
> 
>> The per-node stats in /proc/zoneinfo output are incorrectly inserted
>> between the first populated zone title and its specific stats. This
>> creates confusion while reading or parsing its output.
> 
> I pity anyone who has to write a parser for that mess.

Some userspace parser have faced an issue like this:
https://github.com/prometheus/procfs/issues/386
In the fix commit, they are ignoring per-node stats section.

> 
>> This patch relocates the per-node stats at the beginning for each node,
>> followed by the individual zone statistics. This fix results in a clearer
>> and more consistent output format.
> 
>> Fixes: e2ecc8a79ed4 ("mm, vmstat: print node-based stats in zoneinfo file")
> 
> It's been this way since 2016?  Surely there's a risk of breaking
> existing userspace parsers?

For some of the per-node stats, some application may probe the
/sys/devices/system/node/node*/meminfo (in KB)

There may be a possibility of breaking scripts, but it will make the
output more consistent for future scripts.

Thanks,
Shivank