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

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Message-ID: <53338CFE.3060705@huawei.com>
Date:	Thu, 27 Mar 2014 10:29:18 +0800
From:	Li Zefan <lizefan@...wei.com>
To:	Catalin Marinas <catalin.marinas@....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

(Just came back from travelling)

On 2014/3/22 7:37, Catalin Marinas wrote:
> Hi Li,
> 
> 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?

> I would keep the “clear” part separately as per your first patch. I
> recall people asked in the past to still be able to analyse the reports
> even though kmemleak failed or was disabled.
> 

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