linux-kernel - Re: Work queue questions

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Message-ID: <20120924200809.GC29689@google.com>
Date:	Mon, 24 Sep 2012 13:08:09 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Deepawali Verma <dverma249@...il.com>
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

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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