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 at 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.
