On Tue, 2013-04-02 at 11:25 +0900, Joonsoo Kim wrote: > Hello, Preeti. > > On Mon, Apr 01, 2013 at 12:36:52PM +0530, Preeti U Murthy wrote: > > Hi Joonsoo, > > > > On 04/01/2013 09:38 AM, Joonsoo Kim wrote: > > > Hello, Preeti. > > > > > > > >> > > >> Ideally the children's cpu share must add upto the parent's share. > > >> > > > > > > I don't think so. > > > > > > We should schedule out the parent tg if 5ms is over. As we do so, we can > > > fairly distribute time slice to every tg within short term. If we add > > > the children's cpu share upto the parent's, the parent tg may have > > > large time slice, so it cannot be preempted easily. There may be a latency > > > problem if there are many tgs. > > > > In the case where the #running < sched_nr_latency, the children's > > sched_slices add up to the parent's. > > > > A rq with two tgs,each with 3 tasks. > > > > Each of these tasks have a sched slice of > > [(sysctl_sched_latency / 3) / 2] as of the present implementation. > > > > The sum of the above sched_slice of all tasks of a tg will lead to the > > sched_slice of its parent: sysctl_sched_latency / 2 > > > > This breaks when the nr_running on each tg > sched_nr_latency. However I > > don't know if this is a good thing or a bad thing. > > Ah.. Now I get your point. Yes, you are right and it may be good thing. > With that property, all tasks in the system can be scheduled at least once > in sysctl_sched_latency. sysctl_sched_latency is system-wide configuration, > so my patch may be wrong. With my patch, all tasks in the system cannot be > scheduled at least once in sysctl_sched_latency. Instead, it schedule > all tasks in cfs_rq at least once in sysctl_sched_latency if there is > no other tgs. > > I think that it is real problem that sysctl_sched_min_granularity is not > guaranteed for each task. > Instead of this patch, how about considering low bound? > > if (slice < sysctl_sched_min_granularity) > slice = sysctl_sched_min_granularity;
How many SCHED_IDLE or +nice tasks will fit in that? -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
