Hello, Michel. On Wed, Jul 06, 2016 at 12:12:52PM +0900, Michel Dänzer wrote: > 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).
Oh I see. > 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? Also, what kind of delays matter here? Is it millisec range or micro? > 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? If the flip work doesn't require high priority kthread, both of them can be queued to system_wq and flushed individually on shutdown. The default workqueue now has high enough concurrency that it isn't necessary to worry about getting delayed by other work items. Thanks. -- tejun
