Messages in this thread | | | Subject | Re: [PATCH v3 4/5] sched/pelt: Add a new runnable average signal | From | Valentin Schneider <> | Date | Thu, 20 Feb 2020 16:11:18 +0000 |
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On 20/02/2020 14:36, Vincent Guittot wrote: > I agree that setting by default to SCHED_CAPACITY_SCALE is too much > for little core. > The problem for little core can be fixed by using the cpu capacity instead >
So that's indeed better for big.LITTLE & co. Any reason however for not aligning with the initialization of util_avg ?
With the default MC imbalance_pct (117), it takes 875 utilization to make a single CPU group (with 1024 capacity) overloaded (group_is_overloaded()). For a completely idle CPU, that means forking at least 3 tasks (512 + 256 + 128 util_avg)
With your change, it only takes 2 tasks. I know I'm being nitpicky here, but I feel like those should be aligned, unless we have a proper argument against it - in which case this should also appear in the changelog with so far only mentions issues with util_avg migration, not the fork time initialization.
> @@ -796,6 +794,8 @@ void post_init_entity_util_avg(struct task_struct *p) > } > } > > + sa->runnable_avg = cpu_scale; > + > if (p->sched_class != &fair_sched_class) { > /* > * For !fair tasks do: >> >>> sa->load_avg = scale_load_down(se->load.weight); >>> + } >>> >>> /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */ >>> }
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