linux-kernel - Re: [PATCH] mm, meminit: Serially initialise deferred memory if trace_buf

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Date:   Wed, 15 Nov 2017 14:43:14 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, yasu.isimatu@...il.com,
        koki.sanagi@...fujitsu.com
Subject: Re: [PATCH] mm, meminit: Serially initialise deferred memory if
 trace_buf_size is specified

On Wed, Nov 15, 2017 at 03:28:16PM +0100, Michal Hocko wrote:
> On Wed 15-11-17 14:13:29, Mel Gorman wrote:
> [...]
> > I doubt anyone well. Even the original reporter appeared to pick that
> > particular value just to trigger the OOM.
> 
> Then why do we care at all? The trace buffer size can be configured from
> the userspace if it is not sufficiently large IIRC.
> 

I guess there is the potential that the trace buffer needs to be large
enough early on in boot but I'm not sure why it would need to be that large
to be honest. Bottom line, it's fairly trivial to just serialise meminit
in the event that it's resized from command line. I'm also ok with just
leaving this is as a "don't set the buffer that large" but I don't think
spreading meminit concerns into ftrace is a good idea.

-- 
Mel Gorman
SUSE Labs