linux-kernel - Re: [PATCH v2] gpu: host1x: hw: intr_hw: Remove create

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Message-ID: <20160620151123.GY3262@mtj.duckdns.org>
Date:	Mon, 20 Jun 2016 11:11:23 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Bhaktipriya Shridhar <bhaktipriya96@...il.com>
Cc:	Thierry Reding <thierry.reding@...il.com>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, dri-devel@...ts.freedesktop.org,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] gpu: host1x: hw: intr_hw: Remove create_workqueue

On Sat, Jun 18, 2016 at 02:36:32PM +0530, Bhaktipriya Shridhar wrote:
> System workqueues have been able to handle high level of concurrency
> for a long time now and there's no reason to use dedicated workqueues
> just to gain concurrency. Since the workqueue host->intr_wq is involved
> in sync point interrupts, and sync point wait and is not being used on
> a memory reclaim path, dedicated host->intr_wq has been replaced with the
> use of system_wq.
> 
> Unlike a dedicated per-cpu workqueue created with create_workqueue(),
> system_wq allows multiple work items to overlap executions even on
> the same CPU; however, a per-cpu workqueue doesn't have any CPU
> locality or global ordering guarantees unless the target CPU is
> explicitly specified and thus the increase of local concurrency
> shouldn't make any difference.
> 
> cancel_work_sync() has been used  in _host1x_free_syncpt_irq() to ensure
> that no work is pending by the time exit path runs.

Alternatively, this could have used alloc_workqueue() w/o
WQ_MEM_RECLAIM and used it just as a flush domain.  Either way is
fine.

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun