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To: Jiri Slaby <jslaby@suse.cz>
Cc: linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
        Jiri Slaby <jirislaby@gmail.com>
Subject: Re: kswapd0: wxcessive CPU usage
In-Reply-To: Your message of "Thu, 11 Oct 2012 10:52:28 +0200."
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From: Valdis.Kletnieks@vt.edu
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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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