2021-02-24 14:28:44

by Peter Zijlstra

Subject: [PATCH 4/6] sched: Optimize migration_cpu_stop()

When the purpose of migration_cpu_stop() is to migrate the task to
'any' valid CPU, don't migrate the task when it's already running on a
valid CPU.

Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
---
kernel/sched/core.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1936,14 +1936,25 @@ static int migration_cpu_stop(void *data
complete = true;
}

- if (dest_cpu < 0)
+ if (dest_cpu < 0) {
+ if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask))
+ goto out;
+
dest_cpu = cpumask_any_distribute(&p->cpus_mask);
+ }

if (task_on_rq_queued(p))
rq = __migrate_task(rq, &rf, p, dest_cpu);
else
p->wake_cpu = dest_cpu;

+ /*
+ * XXX __migrate_task() can fail, at which point we might end
+ * up running on a dodgy CPU, AFAICT this can only happen
+ * during CPU hotplug, at which point we'll get pushed out
+ * anyway, so it's probably not a big deal.
+ */
+
} else if (pending) {
/*
* This happens when we get migrated between migrate_enable()'s

2021-03-01 10:22:55

by tip-bot2 for Zqiang

Subject: [tip: sched/urgent] sched: Optimize migration_cpu_stop()

The following commit has been merged into the sched/urgent branch of tip:

Commit-ID: 9eca0f53b1c2f5acb85e84673e263bf996817a24
Gitweb: https://git.kernel.org/tip/9eca0f53b1c2f5acb85e84673e263bf996817a24
Author: Peter Zijlstra <[email protected]>
AuthorDate: Wed, 24 Feb 2021 11:21:35 +01:00
Committer: Peter Zijlstra <[email protected]>
CommitterDate: Mon, 01 Mar 2021 11:02:14 +01:00

sched: Optimize migration_cpu_stop()

When the purpose of migration_cpu_stop() is to migrate the task to
'any' valid CPU, don't migrate the task when it's already running on a
valid CPU.

Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: [email protected]
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Valentin Schneider <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
kernel/sched/core.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 84b657f..ac05afb 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1936,14 +1936,25 @@ static int migration_cpu_stop(void *data)
complete = true;
}

- if (dest_cpu < 0)
+ if (dest_cpu < 0) {
+ if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask))
+ goto out;
+
dest_cpu = cpumask_any_distribute(&p->cpus_mask);
+ }

if (task_on_rq_queued(p))
rq = __migrate_task(rq, &rf, p, dest_cpu);
else
p->wake_cpu = dest_cpu;

+ /*
+ * XXX __migrate_task() can fail, at which point we might end
+ * up running on a dodgy CPU, AFAICT this can only happen
+ * during CPU hotplug, at which point we'll get pushed out
+ * anyway, so it's probably not a big deal.
+ */
+
} else if (pending) {
/*
* This happens when we get migrated between migrate_enable()'s

2021-03-06 11:47:37

by tip-bot2 for Zqiang

Subject: [tip: sched/core] sched: Optimize migration_cpu_stop()

The following commit has been merged into the sched/core branch of tip:

Commit-ID: 3f1bc119cd7fc987c8ed25ffb717f99403bb308c
Gitweb: https://git.kernel.org/tip/3f1bc119cd7fc987c8ed25ffb717f99403bb308c
Author: Peter Zijlstra <[email protected]>
AuthorDate: Wed, 24 Feb 2021 11:21:35 +01:00
Committer: Ingo Molnar <[email protected]>
CommitterDate: Sat, 06 Mar 2021 12:40:21 +01:00

sched: Optimize migration_cpu_stop()

When the purpose of migration_cpu_stop() is to migrate the task to
'any' valid CPU, don't migrate the task when it's already running on a
valid CPU.

Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: [email protected]
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Reviewed-by: Valentin Schneider <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
kernel/sched/core.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 84b657f..ac05afb 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1936,14 +1936,25 @@ static int migration_cpu_stop(void *data)
complete = true;
}

- if (dest_cpu < 0)
+ if (dest_cpu < 0) {
+ if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask))
+ goto out;
+
dest_cpu = cpumask_any_distribute(&p->cpus_mask);
+ }

if (task_on_rq_queued(p))
rq = __migrate_task(rq, &rf, p, dest_cpu);
else
p->wake_cpu = dest_cpu;

+ /*
+ * XXX __migrate_task() can fail, at which point we might end
+ * up running on a dodgy CPU, AFAICT this can only happen
+ * during CPU hotplug, at which point we'll get pushed out
+ * anyway, so it's probably not a big deal.
+ */
+
} else if (pending) {
/*
* This happens when we get migrated between migrate_enable()'s