linux-kernel - Re: workqueue thing

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Message-ID: <20091223065240.GA27225@gondor.apana.org.au>
Date:	Wed, 23 Dec 2009 14:52:40 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Tejun Heo <tj@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Andi Kleen <andi@...stfloor.org>, awalls@...ix.net,
	linux-kernel@...r.kernel.org, jeff@...zik.org, mingo@...e.hu,
	akpm@...ux-foundation.org, rusty@...tcorp.com.au,
	cl@...ux-foundation.org, dhowells@...hat.com, avi@...hat.com,
	johannes@...solutions.net, "David S. Miller" <davem@...emloft.net>,
	Steffen Klassert <steffen.klassert@...unet.com>
Subject: Re: workqueue thing

On Wed, Dec 23, 2009 at 12:37:32PM +0900, Tejun Heo wrote:
> 
> I wrote this before but if something is burning CPU cycles using MT
> workqueues, this can be easily supported by marking such workqueue as
> not concurrency-managed.  ie. Works queued for such workqueues
> wouldn't contribute to the perceived workqueue concurrency and will be
> left to be managed solely by the scheduler.  This will completely
> cover the crypto_wq case which uses MT workqueue with local cpu
> binding.

Right, the main use of workqueues in the crypto subsystem currently
is to perform operations in a process context, e.g., in order to
use SSE instructions on x86, so there is no real parallelism
involved.

However, Steffen Klassert has proposed a parallelisation mechanism
whereby extremely CPU-intensive operations such as encryption may
be split across CPUs.  Steffen, could you repost your padata patches
here?

Thanks,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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