Messages in this thread | | | Date | Mon, 16 Jan 2023 14:56:19 +0000 | From | Dietmar Eggemann <> | Subject | Re: [PATCH v3] sched/fair: unlink misfit task from cpu overutilized |
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On 16/01/2023 12:23, Vincent Guittot wrote: > On Mon, 16 Jan 2023 at 10:07, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: >> >> On 13/01/2023 14:40, Vincent Guittot wrote:
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>>> @@ -6132,6 +6135,7 @@ static inline bool cpu_overutilized(int cpu) >>> unsigned long rq_util_min = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MIN); >>> unsigned long rq_util_max = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MAX); >>> >>> + /* Return true only if the utlization doesn't fit its capacity */ >> >> s/utlization/utilization >> s/its/CPU ? >> >>> return !util_fits_cpu(cpu_util_cfs(cpu), rq_util_min, rq_util_max, cpu); >>> } >> >> cpu_overutilized() is the only place where we now only test for >> !util_fits_cpu(). The new comment says we only care about utilization >> not fitting CPU capacity. >> >> Does this mean the rq uclamp values are not important here and we could >> go back to use fits_capacity()? >> >> Not sure since util_fits_cpu() is still coded differently: > > uclamp_min is not important but uclamp_max still cap the utilization
OK, makes sense.
I.e. we could pass in `rq_util_min = 0` to avoid fetching it unnecessary? In case `fits == 1` before the uclamp_min condition in util_fits_cpu() it doesn't matter if we switch to return `-1` when called from cpu_overutilized(). Detail though ...
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>>> @@ -6940,12 +6945,28 @@ select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target) >>> >>> if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu)) >>> continue; >>> - if (util_fits_cpu(task_util, util_min, util_max, cpu)) >>> + >>> + fits = util_fits_cpu(task_util, util_min, util_max, cpu); >>> + >>> + /* This CPU fits with all capacity and performance requirements */ >> >> In task_fits_cpu() `utilization and performance (better uclamp) >> requirements` term was used. I assume it's the same thing here? >> >>> + if (fits > 0) >>> return cpu; >>> + /* >>> + * Only the min performance (i.e. uclamp_min) doesn't fit. Look >>> + * for the CPU with highest performance capacity. >> ^^^^^^^^^^^^^^^^^^^^ >> >> Do we use a new CPU capacity value `performance capacity (1)` here? >> >> Which I guess is `capacity_orig_of(cpu) - thermal_load_avg(cpu_rq(cpu)`. >> >> I'm asking since util_fits_cpu() still uses: `capacity_orig_thermal (2) >> = capacity_orig - arch_scale_thermal_pressure()` when checking whether >> to return -1. Shouldn't (1) and (2) be the same? > > I'm all in favor of both being capacity_orig_of(cpu) - > thermal_load_avg(cpu_rq(cpu) like the capacity inversion detection
I think we need a handy name for this new capacity value, which seems to be `capacity_orig - capacity reduced by thermal`. And we should either use `thermal_load_avg` or `thermal pressure` for the latter part. And then we should use this consistently in all these places: util_fits_cpu(), feec(), sic().
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