Messages in this thread | | | Date | Mon, 13 Jul 2015 17:29:00 +0900 | From | Byungchul Park <> | Subject | Re: [PATCH v2] sched: let __sched_period() use rq's nr_running |
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On Mon, Jul 13, 2015 at 09:07:01AM +0200, Mike Galbraith wrote: > On Mon, 2015-07-13 at 09:56 +0900, Byungchul Park wrote: > > > and i agree with that it makes latency increase for non-grouped tasks. > > It's not only a latency hit for the root group, it's across the board. > > I suspect an overloaded group foo/bar/baz would prefer small slices over > a large wait as well. I certainly wouldn't want my root group taking the > potentially huge hits that come with stretching period to accommodate an > arbitrarily overloaded /foo/bar/baz.
hello, mike :)
ok, then, do you think that the period have to be stretched by the number of rq's sched entity(e.i. rq->cfs.nr_running)? if it is done with rq->cfs.nr_running, as you can guess, leaf sched entities(e.i. tasks) can have much smaller slice than sysctl_sched_min_granularity. and some code using sysctl_sched_min_granularity need to be fixed in addition.
anyway, current code looks broken since it stretching with local cfs's nr_running. IMHO, it should be stretched with rq->*cfs.nr_running* though leaf tasks can have very small slice, or it should be stretched with rq->*nr_running* to ensure that any task can have a slice which can be comparable to sysctl_sched_min_granularity.
what do you think about this concern?
thank you, byungchul
> > -Mike > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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