linux-kernel - Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace

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Message-ID: <20160504092359.GH29978@dhcp22.suse.cz>
Date:	Wed, 4 May 2016 11:23:59 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>, mgorman@...hsingularity.net,
	Minchan Kim <minchan@...nel.org>,
	Alexander Potapenko <glider@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace

On Wed 04-05-16 11:35:00, Joonsoo Kim wrote:
[...]
> Oops... I think more deeply and change my mind. In recursion case,
> stack is consumed more than 1KB and it would be a problem. I think
> that best approach is using preallocated per cpu entry. It will also
> close recursion detection issue by paying interrupt on/off overhead.

I was thinking about per-cpu solution as well but the thing is that the
stackdepot will allocate and until you drop __GFP_DIRECT_RECLAIM then
per-cpu is not safe. I haven't checked the implamentation of
depot_save_stack but I assume it will not schedule in other places.
-- 
Michal Hocko
SUSE Labs