On 06.07.2016 06:06, Tejun Heo wrote: > On Mon, Jul 04, 2016 at 12:58:32PM +0900, Michel Dänzer wrote: >> On 02.07.2016 22:46, Tejun Heo wrote: >>> On Sat, Jul 02, 2016 at 04:33:50PM +0530, Bhaktipriya Shridhar wrote: >>>> alloc_workqueue replaces deprecated create_singlethread_workqueue(). >>>> >>>> A dedicated workqueue has been used since work items need to be flushed >>>> as a group rather than individually. > > There seem to be two work items involved, the flip one and unpin one. > Provided that there's no ordering requirement between the two, can't > we just flush them individually?
There is an ordering requirement between the two queues, but it's enforced by the driver (by only queuing the unpin work once a flip has completed, which only happens after the corresponding flip work has run). 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?). In contrast, the radeon_unpin_work_func items aren't particularly urgent, and it's okay for several of them to be queued up. So I guess it would actually make sense to use a different workqueue for them, maybe even the default one? >>>> Since there are only a fixed number of work items, explicit concurrency >>>> limit is unnecessary here. >>> >>> What are the involved work items? >> >> drivers/gpu/drm/radeon/radeon_display.c:radeon_flip_work_func() >> >>> Is it safe to run them concurrently? >> >> Concurrently with what exactly? > > The flip and unpin work items. Yes, it's safe to run those concurrently. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer
