linux-kernel - Re: [RFC PATCHSET] workqueue: implement concurrency managed workqueue

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Message-ID: <4AC5F5FB.9050202@s5r6.in-berlin.de>
Date:	Fri, 02 Oct 2009 14:45:47 +0200
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Tejun Heo <tj@...nel.org>
CC:	David Howells <dhowells@...hat.com>, jeff@...zik.org,
	mingo@...e.hu, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, jens.axboe@...cle.com,
	rusty@...tcorp.com.au, cl@...ux-foundation.org,
	arjan@...ux.intel.com
Subject: Re: [RFC PATCHSET] workqueue: implement concurrency managed workqueue

Tejun Heo wrote:
> David Howells wrote:
>> Sounds interesting as a replacement for slow-work.  Some thoughts for you:
>> 
>> The most important features of slow-work are:
>> 
>>  (1) Work items are not re-entered whilst they are executing.
>> 
>>  (2) The slow-work facility keeps references on its work items by asking the
>>      client to get and put on the client's refcount.
>> 
>>  (3) The slow-work facility can create a lot more threads than the number of
>>      CPUs on a system, and the system doesn't grind to a halt if they're all
>>      taken up with long term I/O (performing several mkdirs for example).
>> 
>> I think you have (1) and (3) covered, but I'm unsure about (2).
> 
> Given that slow-work isn't being used too extensively yet, I was
> thinking whether that part could be pushed down to the caller.  Or, we
> can also wrap work and export an interface which supports the get/put
> reference.

BTW, not only slow-work users need reference counting, many existing
regular workqueue users could use it as well.  (Well, I guess I stated
the obvious.)  Currently we have local wrappers for that like these ones:
http://lxr.linux.no/#linux+v2.6.31/drivers/firewire/core-card.c#L212
http://lxr.linux.no/#linux+v2.6.31/drivers/firewire/sbp2.c#L838
-- 
Stefan Richter
-=====-==--= =-=- ---=-
http://arcgraph.de/sr/
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