linux-kernel - Re: Work queue questions

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Message-ID: <CAHCeSFpYZRVasw26q01HO7fj9972wdNiTV0mikiNUuDMi9M0sw@mail.gmail.com>
Date:	Mon, 24 Sep 2012 21:52:14 +0100
From:	Deepawali Verma <dverma249@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Chinmay V S <cvs268@...il.com>,
	Daniel Taylor <Daniel.Taylor@....com>,
	anish singh <anish198519851985@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Work queue questions

Hi Tejun,

I do not have ordering as requirement. I can use system work queue as
well. what is max_active by default for system wq per cpu?

Regards,
Deepa

On Mon, Sep 24, 2012 at 9:08 PM, Tejun Heo <tj@...nel.org> wrote:
> Hello,
>
> On Mon, Sep 24, 2012 at 08:57:40PM +0100, Deepawali Verma wrote:
>> May be I misunderstood, I read in the documentation about max_active.
>> In this case, max_active is 1, but I created three workqueues, do you
>
> I see.  Why are you doing that?  Is there ordering requirement?  Why
> not just use system_unbound_wq?
>
>> mean to say for this case, single thread can process three requests
>> queued up in the three different workqueues.
>
> In the following execution log you posted,
>
>   kworker/u:1-21    [000]   110.964895: task_event: MYTASKJOB2381 XStarted
>   kworker/u:1-21    [000]   110.964909: task_event: MYTASKJOB2381 Xstopped
>   kworker/u:1-21    [000]   110.965137: task_event: MYTASKJOB2382 XStarted
>   kworker/u:1-21    [000]   110.965154: task_event: MYTASKJOB2382 Xstopped
>   kworker/u:5-3724  [000]   110.965311: task_event: MYTASKJOB2383 XStarted
>   kworker/u:5-3724  [000]   110.965325: task_event: MYTASKJOB2383 Xstopped
>
> The first two got executed on the same worker thread but the third one
> is on a different one.  It really looks like you just don't have large
> enough work for scheduler to interleave them or migrate workers to
> different CPUs.
>
> Thanks.
>
> --
> tejun
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