Messages in this thread Patch in this message | | | From | Abel Wu <> | Subject | [RFC PATCH 5/5] sched/fair: favor cpu capacity for idle tasks | Date | Thu, 17 Feb 2022 23:44:01 +0800 |
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Unlike select_idle_sibling() in which we need to find a not-so-bad candidate ASAP, the slowpath gives us more tolerance: ignore sched-idle cpus for idle tasks since they prefer cpu capacity rather than latency, and besides spreading out idle tasks also good for latency of normal tasks.
Signed-off-by: Abel Wu <wuyun.abel@bytedance.com> --- kernel/sched/fair.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1d8f396e6f41..57f1d8c43228 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6007,6 +6007,7 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu); static int find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) { + bool ignore_si = task_h_idle(p); unsigned long load, min_load = ULONG_MAX; unsigned int min_exit_latency = UINT_MAX; u64 latest_idle_timestamp = 0; @@ -6025,7 +6026,13 @@ find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this if (!sched_core_cookie_match(rq, p)) continue; - if (sched_idle_cpu(i)) + /* + * The idle tasks prefer cpu capacity rather than + * latency. Spreading out idle tasks also good for + * latency of normal tasks since they won't suffer + * high cpu wakeup delay. + */ + if (!ignore_si && sched_idle_cpu(i)) return i; if (available_idle_cpu(i)) { -- 2.11.0
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