linux-kernel - Re: Overview of concurrency managed workqueue

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Date:	Sat, 19 Jun 2010 11:08:51 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Tejun Heo <tj@...nel.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	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

> I see.  The thing is that if you have "as soon as possible" + "high
> priority", you're basically required to have a dedicated worker or
> dedicated pool of them.  Making cmwq to support some level of priority
> definitely is possible (multiple prioritized queues or pushing work at
> the front at the simplest) but for such emergency works it doesn't
> make sense to share the usual worker pool, as resource pressure can
> easily make any work wait regardless of where they're in the queue.

I think it's reasonable to just put on front. The individual
items shouldn't take that long, right?

(in fact I have an older patch for work queues which implemented
that) 

> If there are multiple of such use cases, it would make sense to create
> a prioritized worker pools along with prioritized per-cpu queues but
> if there are only a few of them, I think it makes more sense to use
> dedicated threads for them.  Do those threads need to be per-cpu?

Not strictly, although it might be useful on a error flood when
a whole DIMM goes bad.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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