linux-kernel - Re: [patch] workqueue: schedule WORK_CPU_UNBOUND work on wq_unbound

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Date:	Wed, 22 Jul 2015 16:55:12 +0200
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Lai Jiangshan <jiangshanlai@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Rik van Riel <riel@...hat.com>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>
Subject: Re: [patch] workqueue: schedule WORK_CPU_UNBOUND work on
 wq_unbound_cpumask CPUs

On Wed, 2015-07-22 at 10:11 -0400, Tejun Heo wrote:
> On Wed, Jul 22, 2015 at 07:24:46AM +0200, Mike Galbraith wrote:
> > WORK_CPU_UNBOUND work items queued to a bound workqueue always run
> > locally.  This is a good thing normally, but not when the user has
> 
> The constant name used there is a bit misleading but you can't put
> work items which are queued w/ queue_work() on foreign cpus by
> default.  queue_work() has always guaranteed local execution.  The
> problem is that workqueue can't currently tell whether a queue_work()
> user expects cpu locality for correctness or optimization.  It'd be
> great if we introduce queue_work_on_local() or sth and replace
> correctness ones with it but that involves auditing each and every
> queue_work() usage.  If anybody is up for the task, I'd be happy to
> help.

Oh well.  That puts a big dent in the utility of wq_unbound_cpumask, but
too bad.  If someone has a big enough HPC itch, they'll scratch it.

	-Mike

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