On 03/30/2016 05:07 PM, Peter Zijlstra wrote: > On Wed, Mar 30, 2016 at 04:53:05PM +0200, Daniel Wagner wrote: >> From: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx> >> >> Completions have no long lasting callbacks and therefore do not need >> the complex waitqueue variant. Use simple waitqueues which reduces >> the contention on the waitqueue lock. > > Changelog really should have talk about the determinism thing. The last > time you posted this the point was raised that we should wake the > highest prio waiter in the defer case, you did not address this. So we really want to go this road? I didn't find any numbers what the highest count of queued sleepers was in Daniel's complete_all() testing. As for the latest -RT I received only one report from Clark Williams with something like 3 to 9 sleepers waked up during one complete_all() and this happens in the resume code. Based on this, deferring wake-ups from IRQ-context and a RB-tree (or something like that for priority sorting) looks like a lot of complexity and it does not look like we gain much. > Also, you make no mention of the reduction of UINT_MAX to USHORT_MAX and > the implications of that. Wasn't this |To avoid a size increase of struct completion, I spitted the done |field into two half. later he mentions that we can't have 2M sleepers anymore. Sebastian -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
