linux-kernel - Re: Overview of concurrency managed workqueue

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Message-ID: <4C1C8263.9040404@kernel.org>
Date:	Sat, 19 Jun 2010 10:40:03 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Andy Walls <awalls@...metrocast.net>,
	Daniel Walker <dwalker@...eaurora.org>, mingo@...e.hu,
	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 06/19/2010 10:38 AM, Andi Kleen wrote:
> Andy Walls <awalls@...metrocast.net> writes:
>>
>> 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?
> 
> One exceptional case here are things like high priority error handling
> which is rare.
> 
> For example you get an MCE that tells you some of your
> memory got corrupted and you should handle it ASAP.
> Better give it high priority then.
> 
> But it's still a rare event so you don't want dedicated
> threads hanging around for it all time
> (that's what we currently have and it causes all sorts
> of problems)
> 
> So yes I think having a priority mechanism for work items
> is useful.

Wouldn't that be better served by cpu_stop?

Thanks.

-- 
tejun
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