linux-kernel - Re: kmemleak, cpu usage jump out of nowhere

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Date:	Wed, 14 Jul 2010 13:59:01 +0200
From:	Zeno Davatz <zdavatz@...il.com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: kmemleak, cpu usage jump out of nowhere

On Wed, Jul 14, 2010 at 1:54 PM, Catalin Marinas
<catalin.marinas@....com> wrote:
> On Wed, 2010-07-14 at 11:04 +0100, Zeno Davatz wrote:
>> On Wed, Jul 14, 2010 at 11:57 AM, Catalin Marinas
>> <catalin.marinas@....com> wrote:
>> > Zeno Davatz <zdavatz@...il.com> wrote:
>> >> Sometimes in the middle of nowhere all of a sudden all of my 8-cores
>> >> are at 100% CPU usage and my machine really lags and hangs and is not
>> >> useable anymore. Some random process just grabs a bunch CPUs according
>> >> to htop.
>> >
>> > These may be related to the NO_BOOTMEM configuration (I sent a patch in
>> > a separate reply).
>> >
>> > But even when kmemleak scans the memory, it only uses a single thread
>> > and you should only see a single CPU going to 100%. I don't think
>> > kmemleak scanning can explain why all the 8 cores are going up to 100%.
>>
>> I am doing:
>>
>> /usr/src/my2.6> sudo patch -p1 < patch_catalin
>> patching file mm/bootmem.c
>> Hunk #1 FAILED at 435.
>> Hunk #2 FAILED at 461.
>> 2 out of 2 hunks FAILED -- saving rejects to file mm/bootmem.c.rej
>> patching file mm/page_alloc.c
>> Hunk #1 FAILED at 3659.
>> 1 out of 1 hunk FAILED -- saving rejects to file mm/page_alloc.c.rej
>>
>> Any hints why it wont apply? Will this patch be in the next RC?
>
> The patch is against 2.6.35-rc4. I'll send it to Linus and hopefully it
> will get merged during rc.
>
> BTW, you can disable kmemleak scanning by doing:
>
> # echo scan=off > /sys/kernel/debug/kmemleak

Thank you for the hint!

> Do you still get that high CPU usage?

Not at the moment. I disabled

CONFIG_NO_BOOTMEM:

and rebooted onto the new bzImage. No "CPU-bad-mood" at the moment.

Best
Zeno
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