Am 07.07.2016 um 05:32 schrieb Michel Dänzer:
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.
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.
Regards, Christian.