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From: Tejun Heo <tj@kernel.org>
To: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: len.brown@intel.com, linux-pm@vger.kernel.org,
	gregkh@linuxfoundation.org, linux-nvdimm@lists.01.org,
	jiangshanlai@gmail.com, linux-kernel@vger.kernel.org,
	zwisler@kernel.org, pavel@ucw.cz, rafael@kernel.org,
	akpm@linux-foundation.org
Subject: Re: [RFC workqueue/driver-core PATCH 1/5] workqueue: Provide queue_work_near to queue work near a given NUMA node
Date: Mon, 1 Oct 2018 09:01:42 -0700	[thread overview]
Message-ID: <20181001160142.GE270328@devbig004.ftw2.facebook.com> (raw)
In-Reply-To: <ba72f007-84e2-6fe0-b128-d876dadef5f5@linux.intel.com>

Hello,

On Wed, Sep 26, 2018 at 03:19:21PM -0700, Alexander Duyck wrote:
> On 9/26/2018 3:09 PM, Tejun Heo wrote:
> I could just use queue_work_on probably, but is there any issue if I
> am passing CPU values that are not in the wq_unbound_cpumask? That

That should be fine.  If it can't find any available cpu, it'll fall
back to round-robin.  We probably can improve it so that it can
consider the numa distance when falling back.

> was mostly my concern. Also for an unbound queue do I need to worry
> about the hotplug lock? I wasn't sure if that was the case or not as

Issuers don't need to worry about them.

> I know it is called out as something to be concerned with using
> queue_work_on, but in __queue_work the value is just used to
> determine which node to grab a work queue from.

It might be better to leave queue_work_on() to be used for per-cpu
workqueues and introduce queue_work_near() as you suggseted.  I just
don't want it to duplicate the node selection code in it.  Would that
work?

> I forgot to address your question about the advantages. They are
> pretty significant. The test system I was working with was
> initializing 3TB of nvdimm memory per node. If the node is aligned
> it takes something like 24 seconds, whereas an unaligned core can
> take 36 seconds or more.

Oh yeah, sure, numa affinity matters quite a bit on memory heavy
workloads.  I was mistaken that you were adding adding numa affinity
to per-cpu workqueues.

Thanks.

-- 
tejun
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  reply	other threads:[~2018-10-01 16:01 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-26 21:51 [RFC workqueue/driver-core PATCH 0/5] Add NUMA aware async_schedule calls Alexander Duyck
2018-09-26 21:51 ` [RFC workqueue/driver-core PATCH 1/5] workqueue: Provide queue_work_near to queue work near a given NUMA node Alexander Duyck
2018-09-26 21:53   ` Tejun Heo
2018-09-26 22:05     ` Alexander Duyck
2018-09-26 22:09       ` Tejun Heo
2018-09-26 22:19         ` Alexander Duyck
2018-10-01 16:01           ` Tejun Heo [this message]
2018-10-01 21:54             ` Alexander Duyck
2018-10-02 17:41               ` Tejun Heo
2018-10-02 18:23                 ` Alexander Duyck
2018-10-02 18:41                   ` Tejun Heo
2018-10-02 20:49                     ` Alexander Duyck
2018-09-26 21:51 ` [RFC workqueue/driver-core PATCH 2/5] async: Add support for queueing on specific " Alexander Duyck
2018-09-27  0:31   ` Dan Williams
2018-09-27 15:16     ` Alexander Duyck
2018-09-27 19:48       ` Dan Williams
2018-09-27 20:03         ` Alexander Duyck
2018-09-26 21:51 ` [RFC workqueue/driver-core PATCH 3/5] driver core: Probe devices asynchronously instead of the driver Alexander Duyck
2018-09-27  0:48   ` Dan Williams
2018-09-27 15:27     ` Alexander Duyck
2018-09-28  2:48       ` Dan Williams
2018-09-26 21:51 ` [RFC workqueue/driver-core PATCH 4/5] driver core: Use new async_schedule_dev command Alexander Duyck
2018-09-28 17:42   ` Dan Williams
2018-09-26 21:52 ` [RFC workqueue/driver-core PATCH 5/5] nvdimm: Schedule device registration on node local to the device Alexander Duyck
2018-09-28 17:46   ` Dan Williams

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