Messages in this thread | | | From | Vincent Guittot <> | Date | Wed, 13 Jan 2021 17:49:58 +0100 | Subject | Re: [PATCH 3/5] sched/fair: Make select_idle_cpu() proportional to cores |
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On Mon, 11 Jan 2021 at 16:50, Mel Gorman <mgorman@techsingularity.net> wrote: > > From: Peter Zijlstra (Intel) <peterz@infradead.org> > > Instead of calculating how many (logical) CPUs to scan, compute how > many cores to scan. > > This changes behaviour for anything !SMT2. > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> > --- > kernel/sched/core.c | 19 ++++++++++++++----- > kernel/sched/fair.c | 12 ++++++++++-- > 2 files changed, 24 insertions(+), 7 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 15d2562118d1..7bfa73de6a8d 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -7444,11 +7444,20 @@ int sched_cpu_activate(unsigned int cpu) > balance_push_set(cpu, false); > > #ifdef CONFIG_SCHED_SMT > - /* > - * When going up, increment the number of cores with SMT present. > - */ > - if (cpumask_weight(cpu_smt_mask(cpu)) == 2) > - static_branch_inc_cpuslocked(&sched_smt_present); > + do { > + int weight = cpumask_weight(cpu_smt_mask(cpu)); > + extern int sched_smt_weight;
coding style problem
> + > + if (weight > sched_smt_weight) > + sched_smt_weight = weight; > + > + /* > + * When going up, increment the number of cores with SMT present. > + */ > + if (weight == 2) > + static_branch_inc_cpuslocked(&sched_smt_present); > + > + } while (0); > #endif > set_cpu_active(cpu, true); > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index c8d8e185cf3b..0811e2fe4f19 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6010,6 +6010,8 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p > DEFINE_STATIC_KEY_FALSE(sched_smt_present); > EXPORT_SYMBOL_GPL(sched_smt_present); > > +int sched_smt_weight __read_mostly = 1; > + > static inline void set_idle_cores(int cpu, int val) > { > struct sched_domain_shared *sds; > @@ -6124,6 +6126,8 @@ static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int t > > #else /* CONFIG_SCHED_SMT */ > > +#define sched_smt_weight 1 > + > static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target) > { > return -1; > @@ -6136,6 +6140,8 @@ static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd > > #endif /* CONFIG_SCHED_SMT */ > > +#define sis_min_cores 2 > + > /* > * Scan the LLC domain for idle CPUs; this is dynamically regulated by > * comparing the average scan cost (tracked in sd->avg_scan_cost) against the > @@ -6166,10 +6172,12 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t > avg_cost = this_sd->avg_scan_cost + 1; > > span_avg = sd->span_weight * avg_idle; > - if (span_avg > 4*avg_cost) > + if (span_avg > sis_min_cores*avg_cost) > nr = div_u64(span_avg, avg_cost); > else > - nr = 4; > + nr = sis_min_cores; > + > + nr *= sched_smt_weight;
Also, patch 5 will look at all CPUs of a core in select_idle_core so nr will decrement by 1 per core so i don't see the need to multiply by sched_smt_weight one patch 5 is applied
> > time = cpu_clock(this); > } > -- > 2.26.2 >
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