linux-kernel - Re: excessive kworker activity when idle. (was Re: vma corruption in today's -git)

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Message-ID: <AANLkTikP5edK=YSRx7zuNqyfwez8qEHpFumYun6GOPxu@mail.gmail.com>
Date:	Wed, 30 Mar 2011 22:32:11 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Dave Jones <davej@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>
Subject: Re: excessive kworker activity when idle. (was Re: vma corruption in
 today's -git)

On Wed, Mar 30, 2011 at 8:55 PM, Dave Jones <davej@...hat.com> wrote:
>
> I tried that, and wasn't particularly enlightened.
>
> +      6.53%  kworker/1:2  [kernel.kallsyms]  [k] read_hpet
> +      4.83%  kworker/0:0  [kernel.kallsyms]  [k] read_hpet

Go into those, deeper into the callchain. That's how to see what the
upper-level problem is - by seeing who actually calls it. The leafs
themselves (where the time is obviously spent) don't tend to be very
informative, no.

>  > (Powertop can also do it, and is probably a better thing to use, I'm
>  > just used to "perf record" for other reasons, so..)
>
> Tried that too, here's what it said..

Hmm. Powertop is _supposed_ to be able to look into the kwork things
(it has special trace points for it), but as mentioned, the times I've
seen it I've used 'perf', so I haven't actually tried it myself.

                  Linus
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