Messages in this thread Patch in this message | | | Date | Mon, 14 Dec 2020 17:48:24 +0100 | From | Peter Zijlstra <> | Subject | [RFC][PATCH 2/5] sched/fair: Make select_idle_cpu() proportional to cores |
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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> --- kernel/sched/core.c | 19 ++++++++++++++----- kernel/sched/fair.c | 12 ++++++++++-- 2 files changed, 24 insertions(+), 7 deletions(-)
--- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7454,11 +7454,20 @@ 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; + + 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); --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6010,6 +6010,8 @@ static inline int find_idlest_cpu(struct DEFINE_STATIC_KEY_FALSE(sched_smt_present); EXPORT_SYMBOL_GPL(sched_smt_present); +int sched_smt_weight = 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_s #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 #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_s 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; time = cpu_clock(this); }
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