linux-kernel - Re: [PATCH] drm/radeon: Remove deprecated create_singlethread

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Date:	Thu, 7 Jul 2016 12:32:33 +0900
From:	Michel Dänzer <michel@...nzer.net>
To:	Tejun Heo <tj@...nel.org>
Cc:	Bhaktipriya Shridhar <bhaktipriya96@...il.com>,
	Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/radeon: Remove deprecated
 create_singlethread_workqueue

On 06.07.2016 22:45, Tejun Heo wrote:
> On Wed, Jul 06, 2016 at 12:12:52PM +0900, Michel Dänzer wrote:
> 
>> Not being very familiar with the workqueue APIs, I'll describe how it's
>> supposed to work from a driver POV, which will hopefully help you guys
>> decide on the most appropriate alloc_workqueue parameters.
>>
>> There is one flip work queue for each hardware CRTC. At most one
>> radeon_flip_work_func item can be queued for any of them at any time.
>> When a radeon_flip_work_func item is queued, it should be executed ASAP
>> (so WQ_HIGHPRI might be appropriate?).
> 
> Hmmm... the only time WQ_HIGHPRI should be used is when it'd otherwise
> require a kthread w/ nice value at -20.  Would that be the case here?
> What are the consequences of the work item getting delayed?

A page flip may be delayed to a later display refresh cycle.


> 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.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer



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