linux-kernel - Re: [PATCH] mm: be more informative in OOM task list

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Message-ID: <20180702112906.GH19043@dhcp22.suse.cz>
Date:   Mon, 2 Jul 2018 13:29:06 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Rodrigo Freire <rfreire@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: be more informative in OOM task list

On Mon 02-07-18 07:22:13, Rodrigo Freire wrote:
> Hello Michal,
> 
> ----- Original Message ----- 
> > From: "Michal Hocko" <mhocko@...nel.org>
> > To: "Rodrigo Freire" <rfreire@...hat.com>
> > Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org
> > Sent: Monday, July 2, 2018 6:30:43 AM
> > Subject: Re: [PATCH] mm: be more informative in OOM task list
> >
> > On Sun 01-07-18 13:09:40, Rodrigo Freire wrote:
> > > The default page memory unit of OOM task dump events might not be
> > > intuitive for the non-initiated when debugging OOM events. Add
> > > a small printk prior to the task dump informing that the memory
> > > units are actually memory _pages_.
> >
> > Does this really help? I understand the the oom report might be not the
> > easiest thing to grasp but wouldn't it be much better to actually add
> > documentation with clarification of each part of it?
> 
> That would be great: After a quick grep -ri for oom in Documentation,
> I found several other files containing its own OOM behaviour modifier
> configurations. But it indeed lacks a central and canonical Doc file
> which documents the OOM Killer behavior and workflows.
> 
> However, I still stand by my proposed patch: It is unobtrusive, infers
> no performance issue and clarifying: I recently worked in a case (for
> full disclosure: I am a far cry from a MM expert) where the sum of the
> RSS pages made sense when interpreted as real kB pages. Reason: There
> were processes sharing (a good amount of) memory regions, misleading
> the interpretation and that misled not only me, but some other
> colleagues a well: The pages was only sorted out after actually
> inspecting the source code.
> 
> This patch is user-friendly and can be a great time saver to others in
> the community.

Well, all other counters we print are in page units unless explicitly
kB. So I am not sure we really need to do anything but document the
output better. Maybe others will find it more important though.

-- 
Michal Hocko
SUSE Labs