Subject: Re: Overview of concurrency managed workqueue
From: Andy Walls <awalls@md.metrocast.net>
To: Daniel Walker <dwalker@codeaurora.org>
Cc: Tejun Heo <tj@kernel.org>, mingo@elte.hu, linux-kernel@vger.kernel.org,
       jeff@garzik.org, akpm@linux-foundation.org, rusty@rustcorp.com.au,
       cl@linux-foundation.org, dhowells@redhat.com, arjan@linux.intel.com,
       johannes@sipsolutions.net, oleg@redhat.com, axboe@kernel.dk
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Date: Thu, 17 Jun 2010 08:01:06 -0400
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On Wed, 2010-06-16 at 07:05 -0700, Daniel Walker wrote:
> On Wed, 2010-06-16 at 15:45 +0200, Tejun Heo wrote:
> > On 06/16/2010 03:41 PM, Daniel Walker wrote:
> > > Any workqueue that has a thread which can be prioritized from userspace.
> > > As long as there is a thread it can usually be given a priority from
> > > userspace, so any _current_ workqueue which uses a single thread or
> > > multiple threads is an example of what I'm talking about.
> > 
> > Eh... what's the use case for that?  That's just so wrong.  What do
> > you do after a suspend/resume cycle?  Reprioritize all of them from
> > suspend/resume hooks?
> 
> The use case is any situation when the user wants to give higher
> priority to some set of work items, and there's nothing wrong with that.
> In fact there has been a lot of work in the RT kernel related to
> workqueue prioritization ..

I'm going to agree with Tejun, that tweaking worker thread priorities
seems like an odd thing, since they are meant to handle deferable
actions - things that can be put off until later.

If one needs to support Real Time deadlines on deferable actions,
wouldn't using dedicated kernel threads be more deterministic?
Would the user ever up the priority for a workqueue other than a
single-threaded workqueue?

Regards,
Andy

> Daniel


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