linux-kernel - Re: kswapd0: wxcessive CPU usage

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Date:	Thu, 11 Oct 2012 09:44:40 -0400
From:	Valdis.Kletnieks@...edu
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jirislaby@...il.com>
Subject: Re: kswapd0: wxcessive CPU usage

On Thu, 11 Oct 2012 10:52:28 +0200, Jiri Slaby said:
> Hi,
>
> with 3.6.0-next-20121008, kswapd0 is spinning my CPU at 100% for 1
> minute or so.


>  [<ffffffff8116ee05>] ? put_super+0x25/0x40
>  [<ffffffff8116fdd4>] ? grab_super_passive+0x24/0xa0
>  [<ffffffff8116ff99>] ? prune_super+0x149/0x1b0
>  [<ffffffff81131531>] ? shrink_slab+0xa1/0x2d0
>  [<ffffffff8113452d>] ? kswapd+0x66d/0xb60
>  [<ffffffff81133ec0>] ? try_to_free_pages+0x180/0x180
>  [<ffffffff810a2770>] ? kthread+0xc0/0xd0
>  [<ffffffff810a26b0>] ? kthread_create_on_node+0x130/0x130
>  [<ffffffff816a6c9c>] ? ret_from_fork+0x7c/0x90
>  [<ffffffff810a26b0>] ? kthread_create_on_node+0x130/0x130

I don't know what it is, I haven't finished bisecting it - but I can confirm that
I started seeing the same problem 2 or 3 weeks ago.  Note that said call
trace does *NOT* require a suspend - I don't do suspend on my laptop and
I'm seeing kswapd burn CPU with similar traces.

# cat /proc/31/stack
[<ffffffff81110306>] grab_super_passive+0x44/0x76
[<ffffffff81110372>] prune_super+0x3a/0x13c
[<ffffffff810dc52a>] shrink_slab+0x95/0x301
[<ffffffff810defb7>] kswapd+0x5c8/0x902
[<ffffffff8104eea4>] kthread+0x9d/0xa5
[<ffffffff815ccfac>] ret_from_fork+0x7c/0x90
[<ffffffffffffffff>] 0xffffffffffffffff
# cat /proc/31/stack
[<ffffffff8110f5af>] put_super+0x29/0x2d
[<ffffffff8110f637>] drop_super+0x1b/0x20
[<ffffffff81110462>] prune_super+0x12a/0x13c
[<ffffffff810dc52a>] shrink_slab+0x95/0x301
[<ffffffff810defb7>] kswapd+0x5c8/0x902
[<ffffffff8104eea4>] kthread+0x9d/0xa5
[<ffffffff815ccfac>] ret_from_fork+0x7c/0x90
[<ffffffffffffffff>] 0xffffffffffffffff

So at least we know we're not hallucinating. :)




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