linux-kernel - Re: [PATCH] mm/nommu.c:Dynamic alloc/free percpu area for nommu

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Date:	Thu, 8 Apr 2010 17:40:24 +0800
From:	Sonic Zhang <sonic.adi@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	graff yang <graff.yang@...il.com>, dhowells@...hat.com,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	uclinux-dist-devel@...ckfin.uclinux.org
Subject: Re: [PATCH] mm/nommu.c:Dynamic alloc/free percpu area for nommu

On Thu, Apr 8, 2010 at 10:43 AM, Tejun Heo <tj@...nel.org> wrote:
> Hello, Sonic.
>
>> I tested your patch on NOMMU bf561 with SMP enabled. It is compiled
>> and boots without problem. Because there are few percpu data defined
>> in bf561 SMP kernel, the functions in mm/percpu-km.c may not be
>> executed with a simple test. But, since these functions are simple
>> malloc/free, I don't see any problem.
>
> Great, thanks for testing.  Just in case, can you please test with the
> attached module?  In test-pcpu.c, the cmds table directs the module
> what to allocate and free.  { size > 0, tag } entry makes it allocate
> an area with the specified size and tag and { 0, tag } entry makes it
> free all areas with the matching tag.  The existing table makes pretty
> large amount of allocations and might not work very well on nommu
> configuration.  There are also several DEFINE_PER_CPU() instances to
> test module static percpu area alloc/free.  Please insmod/rmmod in
> loop and make sure it doesn't leak any memory or crashes the machine.
>

Tejun,

There is memory leak with you patch. Free memory continuously
decreases when running test_pcpu. After about 30 minutes, kernel hangs
in out_of_memory().


root/> while [ 1 ]; do modprobe test_pcpu; rmmod test_pcpu; cat
proc/meminfo; done


Sonic

> Thanks.
>
> --
> tejun
>
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