* [PATCH 0/2] sched: Spare IPI on single task renice
@ 2019-12-03 16:01 Frederic Weisbecker
2019-12-03 16:01 ` [PATCH 1/2] sched: Spare resched IPI when prio changes on a single fair task Frederic Weisbecker
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Frederic Weisbecker @ 2019-12-03 16:01 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra; +Cc: LKML, Frederic Weisbecker
A couple of patches to avoid disturbing nohz_full CPUs when a single
fair task get its priority changed. I should probably check other sched
policies as well...
Frederic Weisbecker (2):
sched: Spare resched IPI when prio changes on a single fair task
sched: Use fair:prio_changed() instead of ad-hoc implementation
kernel/sched/core.c | 16 ++++++++--------
kernel/sched/fair.c | 2 ++
2 files changed, 10 insertions(+), 8 deletions(-)
--
2.23.0
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH 1/2] sched: Spare resched IPI when prio changes on a single fair task 2019-12-03 16:01 [PATCH 0/2] sched: Spare IPI on single task renice Frederic Weisbecker @ 2019-12-03 16:01 ` Frederic Weisbecker 2019-12-17 12:39 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker 2019-12-03 16:01 ` [PATCH 2/2] sched: Use fair:prio_changed() instead of ad-hoc implementation Frederic Weisbecker 2019-12-04 12:20 ` [PATCH 0/2] sched: Spare IPI on single task renice Peter Zijlstra 2 siblings, 1 reply; 6+ messages in thread From: Frederic Weisbecker @ 2019-12-03 16:01 UTC (permalink / raw) To: Ingo Molnar, Peter Zijlstra; +Cc: LKML, Frederic Weisbecker The runqueue of a fair task being remotely reniced is going to get a resched IPI in order to reassess which task should be the current running on the CPU. However that evaluation is useless if the fair task is running alone, in which case we can spare that IPI, preventing nohz_full CPUs from being disturbed. Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> --- kernel/sched/fair.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 08a233e97a01..6d2560cb24f0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10322,6 +10322,8 @@ prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) if (!task_on_rq_queued(p)) return; + if (rq->cfs.nr_running == 1) + return; /* * Reschedule if we are currently running on this runqueue and * our priority decreased, or if we are not currently running on -- 2.23.0 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* [tip: sched/core] sched: Spare resched IPI when prio changes on a single fair task 2019-12-03 16:01 ` [PATCH 1/2] sched: Spare resched IPI when prio changes on a single fair task Frederic Weisbecker @ 2019-12-17 12:39 ` tip-bot2 for Frederic Weisbecker 0 siblings, 0 replies; 6+ messages in thread From: tip-bot2 for Frederic Weisbecker @ 2019-12-17 12:39 UTC (permalink / raw) To: linux-tip-commits Cc: Peter Zijlstra, Frederic Weisbecker, Ingo Molnar, x86, LKML The following commit has been merged into the sched/core branch of tip: Commit-ID: 7c2e8bbd87db661122e92d71a394dd7bb3ada4d3 Gitweb: https://git.kernel.org/tip/7c2e8bbd87db661122e92d71a394dd7bb3ada4d3 Author: Frederic Weisbecker <frederic@kernel.org> AuthorDate: Tue, 03 Dec 2019 17:01:05 +01:00 Committer: Peter Zijlstra <peterz@infradead.org> CommitterDate: Tue, 17 Dec 2019 13:32:50 +01:00 sched: Spare resched IPI when prio changes on a single fair task The runqueue of a fair task being remotely reniced is going to get a resched IPI in order to reassess which task should be the current running on the CPU. However that evaluation is useless if the fair task is running alone, in which case we can spare that IPI, preventing nohz_full CPUs from being disturbed. Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Link: https://lkml.kernel.org/r/20191203160106.18806-2-frederic@kernel.org --- kernel/sched/fair.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 08a233e..846f50b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10322,6 +10322,9 @@ prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) if (!task_on_rq_queued(p)) return; + if (rq->cfs.nr_running == 1) + return; + /* * Reschedule if we are currently running on this runqueue and * our priority decreased, or if we are not currently running on ^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 2/2] sched: Use fair:prio_changed() instead of ad-hoc implementation 2019-12-03 16:01 [PATCH 0/2] sched: Spare IPI on single task renice Frederic Weisbecker 2019-12-03 16:01 ` [PATCH 1/2] sched: Spare resched IPI when prio changes on a single fair task Frederic Weisbecker @ 2019-12-03 16:01 ` Frederic Weisbecker 2019-12-17 12:39 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker 2019-12-04 12:20 ` [PATCH 0/2] sched: Spare IPI on single task renice Peter Zijlstra 2 siblings, 1 reply; 6+ messages in thread From: Frederic Weisbecker @ 2019-12-03 16:01 UTC (permalink / raw) To: Ingo Molnar, Peter Zijlstra; +Cc: LKML, Frederic Weisbecker set_user_nice() implements its own version of fair::prio_changed() and therefore misses a specific optimization towards nohz_full CPUs that avoid sending an resched IPI to a reniced task running alone. Use the proper callback instead. Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> --- kernel/sched/core.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 90e4b00ace89..66d1af94455e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4540,17 +4540,17 @@ void set_user_nice(struct task_struct *p, long nice) p->prio = effective_prio(p); delta = p->prio - old_prio; - if (queued) { + if (queued) enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); - /* - * If the task increased its priority or is running and - * lowered its priority, then reschedule its CPU: - */ - if (delta < 0 || (delta > 0 && task_running(rq, p))) - resched_curr(rq); - } + if (running) set_next_task(rq, p); + /* + * If the task increased its priority or is running and + * lowered its priority, then reschedule its CPU: + */ + p->sched_class->prio_changed(rq, p, old_prio); + out_unlock: task_rq_unlock(rq, p, &rf); } -- 2.23.0 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* [tip: sched/core] sched: Use fair:prio_changed() instead of ad-hoc implementation 2019-12-03 16:01 ` [PATCH 2/2] sched: Use fair:prio_changed() instead of ad-hoc implementation Frederic Weisbecker @ 2019-12-17 12:39 ` tip-bot2 for Frederic Weisbecker 0 siblings, 0 replies; 6+ messages in thread From: tip-bot2 for Frederic Weisbecker @ 2019-12-17 12:39 UTC (permalink / raw) To: linux-tip-commits Cc: Peter Zijlstra, Frederic Weisbecker, Ingo Molnar, x86, LKML The following commit has been merged into the sched/core branch of tip: Commit-ID: 5443a0be6121d557e12951537e10159e4c61035d Gitweb: https://git.kernel.org/tip/5443a0be6121d557e12951537e10159e4c61035d Author: Frederic Weisbecker <frederic@kernel.org> AuthorDate: Tue, 03 Dec 2019 17:01:06 +01:00 Committer: Peter Zijlstra <peterz@infradead.org> CommitterDate: Tue, 17 Dec 2019 13:32:50 +01:00 sched: Use fair:prio_changed() instead of ad-hoc implementation set_user_nice() implements its own version of fair::prio_changed() and therefore misses a specific optimization towards nohz_full CPUs that avoid sending an resched IPI to a reniced task running alone. Use the proper callback instead. Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Link: https://lkml.kernel.org/r/20191203160106.18806-3-frederic@kernel.org --- kernel/sched/core.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 90e4b00..15508c2 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4540,17 +4540,17 @@ void set_user_nice(struct task_struct *p, long nice) p->prio = effective_prio(p); delta = p->prio - old_prio; - if (queued) { + if (queued) enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); - /* - * If the task increased its priority or is running and - * lowered its priority, then reschedule its CPU: - */ - if (delta < 0 || (delta > 0 && task_running(rq, p))) - resched_curr(rq); - } if (running) set_next_task(rq, p); + + /* + * If the task increased its priority or is running and + * lowered its priority, then reschedule its CPU: + */ + p->sched_class->prio_changed(rq, p, old_prio); + out_unlock: task_rq_unlock(rq, p, &rf); } ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH 0/2] sched: Spare IPI on single task renice 2019-12-03 16:01 [PATCH 0/2] sched: Spare IPI on single task renice Frederic Weisbecker 2019-12-03 16:01 ` [PATCH 1/2] sched: Spare resched IPI when prio changes on a single fair task Frederic Weisbecker 2019-12-03 16:01 ` [PATCH 2/2] sched: Use fair:prio_changed() instead of ad-hoc implementation Frederic Weisbecker @ 2019-12-04 12:20 ` Peter Zijlstra 2 siblings, 0 replies; 6+ messages in thread From: Peter Zijlstra @ 2019-12-04 12:20 UTC (permalink / raw) To: Frederic Weisbecker; +Cc: Ingo Molnar, LKML On Tue, Dec 03, 2019 at 05:01:04PM +0100, Frederic Weisbecker wrote: > A couple of patches to avoid disturbing nohz_full CPUs when a single > fair task get its priority changed. I should probably check other sched > policies as well... Yeah, auditing all that sounds like a good idea. > Frederic Weisbecker (2): > sched: Spare resched IPI when prio changes on a single fair task > sched: Use fair:prio_changed() instead of ad-hoc implementation These look good though, thanks! ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-12-17 12:40 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2019-12-03 16:01 [PATCH 0/2] sched: Spare IPI on single task renice Frederic Weisbecker 2019-12-03 16:01 ` [PATCH 1/2] sched: Spare resched IPI when prio changes on a single fair task Frederic Weisbecker 2019-12-17 12:39 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker 2019-12-03 16:01 ` [PATCH 2/2] sched: Use fair:prio_changed() instead of ad-hoc implementation Frederic Weisbecker 2019-12-17 12:39 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker 2019-12-04 12:20 ` [PATCH 0/2] sched: Spare IPI on single task renice Peter Zijlstra
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