On Wed, Mar 30, 2016 at 05:17:29PM +0200, Sebastian Andrzej Siewior wrote: > 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? Dunno, but at least mention why it wouldn't matter. > 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. Sure, but that equally puts the whole defer thing into question, if we can put a hard cap on the max number (and WARN when exceeded) we're also good. > > 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. That wasn't in this changelog, therefore it wasn't read ;-) -- 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
