linux-kernel - Re: Overview of concurrency managed workqueue

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Message-ID: <4C18D1FD.9060804@kernel.org>
Date:	Wed, 16 Jun 2010 15:30:37 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Daniel Walker <dwalker@...eaurora.org>
CC:	mingo@...e.hu, awalls@...ix.net, linux-kernel@...r.kernel.org,
	jeff@...zik.org, akpm@...ux-foundation.org, rusty@...tcorp.com.au,
	cl@...ux-foundation.org, dhowells@...hat.com,
	arjan@...ux.intel.com, johannes@...solutions.net, oleg@...hat.com,
	axboe@...nel.dk
Subject: Re: Overview of concurrency managed workqueue

On 06/16/2010 03:27 PM, Daniel Walker wrote:
>> Yes, that is.  With new cmwq, a wq can't assume association with
>> specific kthread and thus can't use wq as simple frontend to kthreads,
>> but if somebody wants dedicated kthreads instead of shared ones in
>> units of work, [s]he should be using kthread.
> 
> I'm not talking about coders using workqueues when they should be using
> kthreads .. We're talking about currently existing workqueues. Aren't
> you converting all _current_ workqueues to your system?

Yes, sure I'm but which current users are you talking about?

>> wq does provide nicer tools for synchronization but in general I don't
>> think using kthread is too hard and there aren't too many cases
>> anyway.  If there are many users && kthread is difficult to use
>> directly, we can definitely write up a wrapping layer tho.  But I
>> really think using wq as wrapper around kthreads and manipulating
>> worker thread directly is an abusement.
> 
> It would be a hack the user would have to patch onto there kernel in
> order to get back functionality your taking away.
> 
> I think from your perspective workqueue threads are all used for
> "concurrency management" only, but I don't think that's true. Some will
> be user for prioritization (I'm talking about _current_ workqueues).
> 
> Could you address or ponder how the work items could be prioritized
> under your system?

Again, please give me some examples.

Thanks.

-- 
tejun
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