Messages in this thread Patch in this message | | | From | subhra mazumdar <> | Subject | [PATCH 3/3] sched: limit cpu search and rotate search window for scalability | Date | Mon, 23 Apr 2018 17:41:16 -0700 |
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Lower the lower limit of idle cpu search in select_idle_cpu() and also put an upper limit. This helps in scalability of the search by restricting the search window. Also rotating the search window with help of next_cpu ensures any idle cpu is eventually found in case of high load.
Signed-off-by: subhra mazumdar <subhra.mazumdar@oracle.com> --- kernel/sched/fair.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index d1d4769..62d585b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6279,7 +6279,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t u64 avg_cost, avg_idle; u64 time, cost; s64 delta; - int cpu, nr = INT_MAX; + int cpu, target_tmp, nr = INT_MAX; this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); if (!this_sd) @@ -6297,15 +6297,24 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t if (sched_feat(SIS_PROP)) { u64 span_avg = sd->span_weight * avg_idle; - if (span_avg > 4*avg_cost) + if (span_avg > 2*avg_cost) { nr = div_u64(span_avg, avg_cost); - else - nr = 4; + if (nr > 4) + nr = 4; + } else { + nr = 2; + } } + if (per_cpu(next_cpu, target) != -1) + target_tmp = per_cpu(next_cpu, target); + else + target_tmp = target; + time = local_clock(); - for_each_cpu_wrap(cpu, sched_domain_span(sd), target) { + for_each_cpu_wrap(cpu, sched_domain_span(sd), target_tmp) { + per_cpu(next_cpu, target) = cpu; if (!--nr) return -1; if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) -- 2.9.3
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