linux-kernel - Re: udevd high cpu hogging in kernel-2.6.34 git8 to git-13

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Message-ID: <4C1A4B70.2010402@gmail.com>
Date:	Thu, 17 Jun 2010 09:21:04 -0700
From:	JD <jd1008@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: udevd high cpu hogging in kernel-2.6.34   git8 to git-13



On 05/27/2010 11:10 PM, Jiri Slaby wrote:
> Added lkml back to CC.
>
> On 05/28/2010 08:06 AM, JD wrote:
>    
>> But here goes:
>> I have seen this behaviour in all the git releases from git8
>> to the current 2.6.34-git13
>>
>> I have some of the analysis based on strace, and kernel stack
>> trace.
>> Instead of backing out the whole code for the new udevd, perhaps
>> it (udevd) should sleep for some time before polling the same fd
>> again.
>>      
> So if you see in the strace output the poll to return immediately with
> out fd being an anon_inode (check /proc/pid_of_udev/fd/), it is the
> issue. AFAIK, it was not fixed upstream yet.
>
> So could you try to revert a7cf4145b?
>
>    
As promised, I tested the patch submitted by Eric Paris
(See http://marc.info/?l=linux-kernel&m=127479018618584&w=2).
I patched kernel-2.6.34-git13 with it, without reverting a7cf4145b.
The thing is it works and works extremely well.
The behaviour is back to what it used to be: Only 3 udevd
threads, as in before git8, and they do not consume any
cpu bandwidth that I can see. It is well below the threshold
of 1% .

Also, it seems that it has been picked up by upstream. Compiled
and booted 2.6.34-git16 and all is well.

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