linux-kernel - Re: kswapd0: excessive CPU usage

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Date:	Sun, 04 Nov 2012 12:26:34 +0100
From:	Zdenek Kabelac <zkabelac@...hat.com>
To:	Jiri Slaby <jslaby@...e.cz>
CC:	Mel Gorman <mgorman@...e.de>, Valdis.Kletnieks@...edu,
	Jiri Slaby <jirislaby@...il.com>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: kswapd0: excessive CPU usage

Dne 2.11.2012 20:45, Jiri Slaby napsal(a):
> On 11/02/2012 11:53 AM, Jiri Slaby wrote:
>> On 11/02/2012 11:44 AM, Zdenek Kabelac wrote:
>>>>> Yes, applying this instead of the revert fixes the issue as well.
>>>
>>> I've applied this patch on 3.7.0-rc3 kernel - and I still see excessive
>>> CPU usage - mainly  after  suspend/resume
>>>
>>> Here is just simple  kswapd backtrace from running kernel:
>>
>> Yup, this is what we were seeing with the former patch only too. Try to
>> apply the other one too:
>> https://patchwork.kernel.org/patch/1673231/
>>
>> For me I would say, it is fixed by the two patches now. I won't be able
>> to report later, since I'm leaving to a conference tomorrow.
>
> Damn it. It recurred right now, with both patches applied. After I
> started a java program which consumed some more memory. Though there are
> still 2 gigs free, kswap is spinning:
> [<ffffffff810b00da>] __cond_resched+0x2a/0x40
> [<ffffffff811318a0>] shrink_slab+0x1c0/0x2d0
> [<ffffffff8113478d>] kswapd+0x66d/0xb60
> [<ffffffff810a25d0>] kthread+0xc0/0xd0
> [<ffffffff816aa29c>] ret_from_fork+0x7c/0xb0
> [<ffffffffffffffff>] 0xffffffffffffffff
>

Yep - wanted to report myself again and noticed your replay.

Yes - I've now also both patches installed - and I still observe kswapd eating 
my CPU.  It seems (at least for me) that  prior suspend and resume is way to 
trigger it more frequently.

However there is a change in behaviour - while before kswapd was running 
almost indefinitely now the> CPU spikes are in the range of minutes.
(i.e. uptime  ~2days -   kswapd has over 32minutes CPU time)
My machine has 4GB, and no swap (disabled)

firefox (22mins), thunderbird(3mins) and pidgin(0.5min) are the 3 most memory 
and CPU hungry apps for this moment.

Zdenek


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