linux-kernel - Re: [PATCHSET wq/for-3.10] workqueue: NUMA affinity for unbound workqueues

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Message-ID: <20130324185506.GA4378@htj.dyndns.org>
Date:	Sun, 24 Mar 2013 11:55:06 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Lai Jiangshan <eag0628@...il.com>
Cc:	laijs@...fujitsu.com, axboe@...nel.dk, jack@...e.cz,
	fengguang.wu@...el.com, jmoyer@...hat.com, zab@...hat.com,
	linux-kernel@...r.kernel.org, herbert@...dor.apana.org.au,
	davem@...emloft.net, linux-crypto@...r.kernel.org
Subject: Re: [PATCHSET wq/for-3.10] workqueue: NUMA affinity for unbound
 workqueues

Hey, Lai.

On Mon, Mar 25, 2013 at 12:04:19AM +0800, Lai Jiangshan wrote:
> example:
> node0(cpu0,cpu1),node1(cpu2,cpu3),
> wq's cpumask: 1,3
> the pwq of this wq on the node1's cpumask: 3
> current online cpu: 0-2.
> so the cpumask of worker tasks of the pwq on node1 is actually cpu_all_mask.
> so the work scheduled from cpu2 can be executed on cpu0 or cpu2.
> we expect it is executed on cpu1 only.

Ah, right.  I was hoping to avoid doing pwq swaps on CPU hot[un]plugs
doing everything on possible mask.  Looks like we'll need some
massaging after all.

> It can be fixed by swapping pwqs(node's pwq <-> default pwq)
> when cpuhotplug. But could you reschedule this patchset to wq/for-3.11?

We're still only at -rc4 meaning we still have plenty of time to
resolve whatever issues which come up, so I think I'm still gonna
target 3.10.

> the whole patchset is more complicated than my brain.

It isn't that complex, is it?  I mean, the difficult part - using
multiple pwqs on unbound wq - already happened, and even that wasn't
too complex as it in most part synchronized the behaviors between
per-cpu and unbound workqueues.  All that NUMA support is doing is
mapping different pwqs to different issuing CPUs.

Thanks.

-- 
tejun
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