linux-kernel - Re: 2.6.39-rc4+: Kernel leaking memory during FS scanning, regression?

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Message-ID: <BANLkTi==7UeCPf0WfD66f1jMXV7j8wsWEA@mail.gmail.com>
Date:	Wed, 27 Apr 2011 11:28:52 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Bruno Prémont <bonbons@...ux-vserver.org>,
	Mike Frysinger <vapier.adi@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org,
	"Paul E. McKenney" <paul.mckenney@...aro.org>,
	Pekka Enberg <penberg@...nel.org>
Subject: Re: 2.6.39-rc4+: Kernel leaking memory during FS scanning, regression?

On 25 April 2011 17:31, Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 2011/4/25 Bruno Prémont <bonbons@...ux-vserver.org>:
>> kmemleak reports 86681 new leaks between shortly after boot and -2 state.
>> (and 2348 additional ones between -2 and -4).
>
> I wouldn't necessarily trust kmemleak with the whole RCU-freeing
> thing. In your slubinfo reports, the kmemleak data itself also tends
> to overwhelm everything else - none of it looks unreasonable per se.

Kmemleak reports that it couldn't find any pointers to those objects
when scanning the memory. In theory, it is safe with RCU since objects
queued for freeing via the RCU are in a linked list and still
referred.

There are of course false positives, usually when pointers are stored
in some structures not scanned by kmemleak (e.g. some arrays allocated
with alloc_pages which are not explicitly tracked by kmemleak) but I
haven't seen any related to RCU (yet).

-- 
Catalin
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