Re: [PATCH] drm/radeon: Remove deprecated create_singlethread_workqueue

From	Tejun Heo <tj@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] drm/radeon: Remove deprecated create_singlethread_workqueue
Date	2016-07-12 20:00 +0200
Message-ID	<rUa8q-8da-11@gated-at.bofh.it> (permalink)
References	(4 earlier) <rRLxv-3L0-1@gated-at.bofh.it> <rRVnc-1pJ-19@gated-at.bofh.it> <rS8X8-1QG-3@gated-at.bofh.it> <rSwZr-Eo-3@gated-at.bofh.it> <rSwZr-Eo-1@gated-at.bofh.it>
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Hello,

On Fri, Jul 08, 2016 at 02:52:30PM +0900, Michel Dänzer wrote:
> On 07.07.2016 16:43, Christian König wrote:
> >>> Also, what kind of delays matter here?  Is it millisec range or micro?
> >> It can be the latter in theory, but normally rather the former.
> > 
> > Well to be precise with a typical 1920x1080@60 resolution you have about
> > 2.16ms time under ideal conditions for the flip.
> > 
> > So using the high priority queue still sounds like a good idea to me.
> 
> How did you arrive at 2.16ms?
> 
> Userspace can call the ioctl up to one full refresh cycle ahead of time,
> which is ~16ms at 60 Hz. On the other hand userspace can also call the
> ioctl arbitrarily close to the vertical blank period, in which case even
> a delay of just 1ms (or even significantly less) may cause the flip to
> be delayed by one refresh cycle.

If there's too long a delay, the outcome is missing the refresh cycle,
right?  Hmmm... yeah, WQ_HIGHPRI probably is the right answer here.
Bhaktipriya, can you please update the patch to use a dedicated
workqueue with WQ_HIGHPRI?

Thanks.

-- 
tejun

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Re: [PATCH] drm/radeon: Remove deprecated  create_singlethread_workqueue Tejun Heo <tj@kernel.org> - 2016-07-12 20:00 +0200
  [PATCH v2] drm/radeon: Remove deprecated  create_singlethread_workqueue Bhaktipriya Shridhar <bhaktipriya96@gmail.com> - 2016-07-16 13:40 +0200
    Re: [PATCH v2] drm/radeon: Remove deprecated  create_singlethread_workqueue Tejun Heo <tj@kernel.org> - 2016-07-19 02:50 +0200

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