Messages in this thread | | | Subject | Re: [RFC PATCH] check_preempt_tick should not compare vruntime with wall time | From | Mike Galbraith <> | Date | Tue, 14 Sep 2010 04:10:52 +0200 |
| |
On Mon, 2010-09-13 at 12:16 -0400, Mathieu Desnoyers wrote: > * Peter Zijlstra (peterz@infradead.org) wrote: > > On Mon, 2010-09-13 at 09:56 -0400, Mathieu Desnoyers wrote: > [...] > > > > static void > > > > check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) > > > > { > > > > - unsigned long ideal_runtime, delta_exec; > > > > + unsigned long slice = sched_slice(cfs_rq, curr); > > > > > > So you still compute the sched_slice(), based on sched_period(), based on > > > sysctl_sched_min_granularity *= nr_running when there are more than nr_latency > > > running threads. > > > > What's wrong with that? I keep asking you, you keep not giving an > > answer. Stop focussing on nr_latency, its an by produce not a > > fundamental entity. > > > > period := max(latency, min_gran * nr_running) > > > > See, no nr_latency -- the one and only purpose of nr_latency is avoiding > > that multiplication when possible. > > OK, the long IRC discussions we just had convinced me that the current scheme > takes things into account by adapting the granularity dynamically, but also got > me to notice that check_preempt seems to compare vruntime with wall time, which > is utterly incorrect. So maybe all my patch was doing was to expose this bug:
It's not wall time, it's just a distance. But I'm not attached to it by any means, if something else works better, do that :)
-Mike
| |