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

Michel Dänzer
2016-07-07T04:16:50Z

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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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