On Tue, 6 Apr 2021 at 06:11, Ricardo Neri <[email protected]> wrote: > > Introduce arch_sched_asym_prefer_early() so that architectures with SMT > can delay the decision to label a candidate busiest group as > group_asym_packing. > > When using asymmetric packing, high priority idle CPUs pull tasks from > scheduling groups with low priority CPUs. The decision on using asymmetric > packing for load balancing is done after collecting the statistics of a > candidate busiest group. However, this decision needs to consider the > state of SMT siblings of dst_cpu. > > Cc: Aubrey Li <[email protected]> > Cc: Ben Segall <[email protected]> > Cc: Daniel Bristot de Oliveira <[email protected]> > Cc: Dietmar Eggemann <[email protected]> > Cc: Joel Fernandes (Google) <[email protected]> > Cc: Mel Gorman <[email protected]> > Cc: Quentin Perret <[email protected]> > Cc: Srinivas Pandruvada <[email protected]> > Cc: Steven Rostedt <[email protected]> > Cc: Tim Chen <[email protected]> > Reviewed-by: Len Brown <[email protected]> > Signed-off-by: Ricardo Neri <[email protected]> > --- > include/linux/sched/topology.h | 1 + > kernel/sched/fair.c | 11 ++++++++++- > 2 files changed, 11 insertions(+), 1 deletion(-) > > diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h > index 8f0f778b7c91..663b98959305 100644 > --- a/include/linux/sched/topology.h > +++ b/include/linux/sched/topology.h > @@ -57,6 +57,7 @@ static inline int cpu_numa_flags(void) > #endif > > extern int arch_asym_cpu_priority(int cpu); > +extern bool arch_sched_asym_prefer_early(int a, int b); > > struct sched_domain_attr { > int relax_domain_level; > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 4ef3fa0d5e8d..e74da853b046 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -106,6 +106,15 @@ int __weak arch_asym_cpu_priority(int cpu) > return -cpu; > } > > +/* > + * For asym packing, early check if CPUs with higher priority should be > + * preferred. On some architectures, more data is needed to make a decision. > + */ > +bool __weak arch_sched_asym_prefer_early(int a, int b) > +{ > + return sched_asym_prefer(a, b); > +} > + > /* > * The margin used when comparing utilization with CPU capacity. > * > @@ -8458,7 +8467,7 @@ static inline void update_sg_lb_stats(struct lb_env > *env, > if (!local_group && env->sd->flags & SD_ASYM_PACKING && > env->idle != CPU_NOT_IDLE && > sgs->sum_h_nr_running && > - sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu)) { > + arch_sched_asym_prefer_early(env->dst_cpu, > group->asym_prefer_cpu)) {
If itmt set arch_sched_asym_prefer_early to true all groups will be set as group_asym_packing unconditionally which is wrong. The state has to be set only when we want asym packing migration > sgs->group_asym_packing = 1; > } > > -- > 2.17.1 >
