Date: Sat, 19 Jun 2010 11:08:51 +0200
From: Andi Kleen <andi@firstfloor.org>
To: Tejun Heo <tj@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>, Andy Walls <awalls@md.metrocast.net>,
       Daniel Walker <dwalker@codeaurora.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
Subject: Re: Overview of concurrency managed workqueue
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> 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@linux.intel.com -- Speaking for myself only.
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