Messages in this thread | | | Date | Tue, 6 Dec 2022 18:22:41 +0100 | Subject | Re: [PATCH v2 1/7] sched/fair: Generalize asym_packing logic for SMT local sched group | From | Dietmar Eggemann <> |
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On 22/11/2022 21:35, Ricardo Neri wrote: > When balancing load between two physical cores, an idle destination CPU can > help another core only if all of its SMT siblings are also idle. Otherwise, > there is not increase in throughput. It does not matter whether the other > core is composed of SMT siblings. > > Simply check if there are any tasks running on the local group and the > other core has exactly one busy CPU before proceeding. Let > find_busiest_group() handle the case of more than one busy CPU. This is > true for SMT2, SMT4, SMT8, etc.
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> Changes since v1: > * Reworded commit message and inline comments for clarity. > * Stated that this changeset does not impact STM4 or SMT8. > --- > kernel/sched/fair.c | 29 +++++++++-------------------- > 1 file changed, 9 insertions(+), 20 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index e4a0b8bd941c..18c672ff39ef 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -8900,12 +8900,10 @@ static bool asym_smt_can_pull_tasks(int dst_cpu, struct sd_lb_stats *sds, > struct sched_group *sg)
I'm not sure why you change asym_smt_can_pull_tasks() together with removing SD_ASYM_PACKING from SMT level (patch 5/7)?
update_sg_lb_stats()
... && env->sd->flags & SD_ASYM_PACKING && .. && sched_asym() ^^^^^^^^^^^^ sched_asym()
if ((sds->local->flags & SD_SHARE_CPUCAPACITY) || (group->flags & SD_SHARE_CPUCAPACITY)) return asym_smt_can_pull_tasks() ^^^^^^^^^^^^^^^^^^^^^^^^^
So x86 won't have a sched domain with SD_SHARE_CPUCAPACITY and SD_ASYM_PACKING anymore. So sched_asym() would call sched_asym_prefer() directly on MC. What do I miss here?
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