From: Mel Gorman mgorman@techsingularity.net
mainline inclusion from mainline-5.12-rc1 commit e6e0dc2d5497f7f3ed970052917e2923c6f453f4 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I41A4K CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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SIS_AVG_CPU was introduced as a means of avoiding a search when the average search cost indicated that the search would likely fail. It was a blunt instrument and disabled by commit 4c77b18cf8b7 ("sched/fair: Make select_idle_cpu() more aggressive") and later replaced with a proportional search depth by commit 1ad3aaf3fcd2 ("sched/core: Implement new approach to scale select_idle_cpu()").
While there are corner cases where SIS_AVG_CPU is better, it has now been disabled for almost three years. As the intent of SIS_PROP is to reduce the time complexity of select_idle_cpu(), lets drop SIS_AVG_CPU and focus on SIS_PROP as a throttling mechanism.
Signed-off-by: Mel Gorman mgorman@techsingularity.net Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Vincent Guittot vincent.guittot@linaro.org Link: https://lkml.kernel.org/r/20210125085909.4600-2-mgorman@techsingularity.net Signed-off-by: Zheng Zucheng zhengzucheng@huawei.com Reviewed-by: Chen Hui judy.chenhui@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- kernel/sched/fair.c | 20 +++++++++----------- kernel/sched/features.h | 1 - 2 files changed, 9 insertions(+), 12 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a7d34016b6be..be1d3bcb6e11 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6170,7 +6170,6 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t { struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask); struct sched_domain *this_sd; - u64 avg_cost, avg_idle; u64 time; int this = smp_processor_id(); int cpu, nr = INT_MAX; @@ -6179,18 +6178,17 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t if (!this_sd) return -1;
- /* - * Due to large variance we need a large fuzz factor; hackbench in - * particularly is sensitive here. - */ - avg_idle = this_rq()->avg_idle / 512; - avg_cost = this_sd->avg_scan_cost + 1; + if (sched_feat(SIS_PROP)) { + u64 avg_cost, avg_idle, span_avg;
- if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost) - return -1; + /* + * Due to large variance we need a large fuzz factor; + * hackbench in particularly is sensitive here. + */ + avg_idle = this_rq()->avg_idle / 512; + avg_cost = this_sd->avg_scan_cost + 1;
- if (sched_feat(SIS_PROP)) { - u64 span_avg = sd->span_weight * avg_idle; + span_avg = sd->span_weight * avg_idle; if (span_avg > 4*avg_cost) nr = div_u64(span_avg, avg_cost); else diff --git a/kernel/sched/features.h b/kernel/sched/features.h index f1bf5e12d889..129ca8f50cf5 100644 --- a/kernel/sched/features.h +++ b/kernel/sched/features.h @@ -54,7 +54,6 @@ SCHED_FEAT(TTWU_QUEUE, true) /* * When doing wakeups, attempt to limit superfluous scans of the LLC domain. */ -SCHED_FEAT(SIS_AVG_CPU, false) SCHED_FEAT(SIS_PROP, true)
/*