diff options
| author | Srikar Dronamraju <srikar@linux.vnet.ibm.com> | 2019-12-06 22:54:22 +0530 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2020-01-28 21:37:08 +0100 |
| commit | bec2860a2bd6cd38ea34434d04f4033eb32f0f31 (patch) | |
| tree | 42f83c328e57464ba8e42eb731ced97f197ca168 /kernel/sched/fair.c | |
| parent | 918229cdd5abb50d8a2edfcd8dc6b6bc53afd765 (diff) | |
sched/fair: Optimize select_idle_core()
Currently we loop through all threads of a core to evaluate if the core is
idle or not. This is unnecessary. If a thread of a core is not idle, skip
evaluating other threads of a core. Also while clearing the cpumask, bits
of all CPUs of a core can be cleared in one-shot.
Collecting ticks on a Power 9 SMT 8 system around select_idle_core
while running schbench shows us
(units are in ticks, hence lesser is better)
Without patch
N Min Max Median Avg Stddev
x 130 151 1083 284 322.72308 144.41494
With patch
N Min Max Median Avg Stddev Improvement
x 164 88 610 201 225.79268 106.78943 30.03%
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Link: https://lkml.kernel.org/r/20191206172422.6578-1-srikar@linux.vnet.ibm.com
Diffstat (limited to 'kernel/sched/fair.c')
| -rw-r--r-- | kernel/sched/fair.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 25dffc03f0f6..1a0ce83e835a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5787,10 +5787,12 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int bool idle = true; for_each_cpu(cpu, cpu_smt_mask(core)) { - __cpumask_clear_cpu(cpu, cpus); - if (!available_idle_cpu(cpu)) + if (!available_idle_cpu(cpu)) { idle = false; + break; + } } + cpumask_andnot(cpus, cpus, cpu_smt_mask(core)); if (idle) return core; |