Messages in this thread | | | From | Vincent Guittot <> | Date | Thu, 31 Oct 2019 17:31:39 +0100 | Subject | Re: [Patch v4 4/6] sched/fair: update cpu_capcity to reflect thermal pressure |
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On Thu, 31 Oct 2019 at 17:17, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: > > On 31.10.19 16:48, Vincent Guittot wrote: > > On Thu, 31 Oct 2019 at 16:38, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: > >> > >> On 31.10.19 11:53, Qais Yousef wrote: > >>> On 10/28/19 16:30, Peter Zijlstra wrote: > >>>> On Wed, Oct 23, 2019 at 01:28:40PM +0100, Qais Yousef wrote: > >>>>> On 10/22/19 16:34, Thara Gopinath wrote: > > [...] > > >>> To make sure I got this correctly - it's because avg_thermal.load_avg > >>> represents delta_capacity which is already a 'converted' form of load. So this > >>> makes avg_thermal.load_avg a util_avg really. Correct? > >>> > >>> If I managed to get it right somehow. It'd be nice if we can do inverse > >>> conversion on delta_capacity so that avg_thermal.{load_avg, util_avg} meaning > >>> is consistent across the board. But I don't feel strongly about it if this gets > >>> documented properly. > >> > >> So why can't we use rq->avg_thermal.util_avg here? Since capacity is > >> closer to util than to load? > >> > >> Is it because you want to use the influence of ___update_load_sum(..., > >> unsigned long load eq. per-cpu delta_capacity in your signal? > >> > >> Why not call it this way then? > > > > util_avg tracks a binary state with 2 fixed weights: running(1024) vs > > not running (0) > > In the case of thermal pressure, we want to track how much pressure is > > put on the CPU: capping to half the max frequency is not the same as > > capping only 10% > > load_avg is not boolean but you set the weight you want to apply and > > this weight reflects the amount of pressure. > > I see. This is what I meant by 'load (weight) eq. per-cpu delta_capacity > (pressure)'. > > > >> diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c > >> index 38210691c615..d3035457483f 100644 > >> --- a/kernel/sched/pelt.c > >> +++ b/kernel/sched/pelt.c > >> @@ -357,9 +357,9 @@ int update_thermal_load_avg(u64 now, struct rq *rq, > >> u64 capacity) > >> { > >> if (___update_load_sum(now, &rq->avg_thermal, > >> capacity, > >> - capacity, > >> - capacity)) { > >> - ___update_load_avg(&rq->avg_thermal, 1, 1); > >> + 0, > >> + 0)) { > >> + ___update_load_avg(&rq->avg_thermal, 1, 0); > >> return 1; > >> } > > So we could call it this way since we don't care about runnable_load or > util?
one way or the other is quite similar but the current solution is aligned with other irq, rt, dl signals which duplicates the same state in each fields
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