linux-kernel - Re: Why is kslowd accumulating so much CPU time?

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Message-ID: <AANLkTilqc0jpwnIwe3OIQvB9avaXXzrBK4Hz0huESygy@mail.gmail.com>
Date:	Sun, 13 Jun 2010 18:23:45 +1000
From:	Dave Airlie <airlied@...il.com>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	Dave Airlie <airlied@...hat.com>,
	David Howells <dhowells@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Why is kslowd accumulating so much CPU time?

On Thu, Jun 10, 2010 at 4:36 AM, Theodore Ts'o <tytso@....edu> wrote:
>
> My laptop is running 2.6.35-rc2 (plus a few patches) and after not quite
> four hours of beeing booted (3:45 to be precise), top shows that kslowd
> has accumulated as surprising amount of CPU time.  From top display:
>
>  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>  6173 root      15  -5     0    0    0 S    6  0.0  10:42.91 kslowd001
>  1219 root      15  -5     0    0    0 S    5  0.0  11:00.68 kslowd000
>  1765 root      15  -5     0    0    0 S    5  0.0  10:59.20 kslowd002
>  6784 root      15  -5     0    0    0 S    4  0.0  10:34.37 kslowd003
>  4946 root      20   0  144m  34m  17m S    3  0.9   2:24.62 Xorg
>
> This came up because I was trying to figure out why mouse response was
> being so jerky.  There aren't that many users of slow-work, and given
> that I'm not using cifs, fscache, gfs2, my suspicions are falling on
> drivers/gpu/drm/drm_crtc_helper.c (Would this be something that would be
> in use on a Lenovo T400 laptop?)
>
> Is there any way to easily see what is scheduling themselves to use the
> slow workqueue?

Its an output polling feature of KMS, however it shouldn't cause
disruption elsewhere, but we are holding a mutex in there that there
isn't a real need to hold, so I suspect I'll drop that.

What GPU is it?

Dave.
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