linux-kernel - Re: [PATCH v2 1/3] kmemleak: allow freeing internal objects after kmemleak was disabled

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Message-ID: <20140327122139.GH20298@arm.com>
Date:	Thu, 27 Mar 2014 12:21:39 +0000
From:	Catalin Marinas <catalin.marinas@....com>
To:	Li Zefan <lizefan@...wei.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH v2 1/3] kmemleak: allow freeing internal objects after
 kmemleak was disabled

On Thu, Mar 27, 2014 at 02:29:18AM +0000, Li Zefan wrote:
> On 2014/3/22 7:37, Catalin Marinas wrote:
> > On 17 Mar 2014, at 04:07, Li Zefan <lizefan@...wei.com> wrote:
> >> Currently if kmemleak is disabled, the kmemleak objects can never be freed,
> >> no matter if it's disabled by a user or due to fatal errors.
> >>
> >> Those objects can be a big waste of memory.
> >>
> >>  OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME
> >> 1200264 1197433  99%    0.30K  46164       26    369312K kmemleak_object
> >>
> >> With this patch, internal objects will be freed immediately if kmemleak is
> >> disabled explicitly by a user. If it's disabled due to a kmemleak error,
> >> The user will be informed, and then he/she can reclaim memory with:
> >>
> >> 	# echo off > /sys/kernel/debug/kmemleak
> >>
> >> v2: use "off" handler instead of "clear" handler to do this, suggested
> >>    by Catalin.
> > 
> > I think there was a slight misunderstanding. My point was about "echo
> > scan=off” before “echo off”, they can just be squashed into the
> > same action of the latter.
> 
> I'm not sure if I understand correctly, so you want the "off" handler to
> stop the scan thread but it will never free kmemleak objects until the 
> user explicitly trigger the "clear" action, right?

Yes. That's just in case someone wants to stop kmemleak but still
investigate some previously reported leaks.

Thanks.

-- 
Catalin
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