* [PATCH v2] sched/core: Reduce cost of sched_move_task when config autogroup
@ 2023-03-21 6:44 wuchi
2023-03-21 9:36 ` Peter Zijlstra
2023-03-22 9:22 ` [tip: sched/core] " tip-bot2 for wuchi
0 siblings, 2 replies; 4+ messages in thread
From: wuchi @ 2023-03-21 6:44 UTC (permalink / raw)
To: mingo, peterz, juri.lelli, vincent.guittot, dietmar.eggemann,
rostedt, bsegall, mgorman, bristot, vschneid
Cc: linux-kernel
Some sched_move_task calls are useless because that
task_struct->sched_task_group maybe not changed (equals task_group
of cpu_cgroup) when system enable autogroup. So do some checks in
sched_move_task.
sched_move_task eg:
task A belongs to cpu_cgroup0 and autogroup0, it will always belong
to cpu_cgroup0 when do_exit. So there is no need to do {de|en}queue.
The call graph is as follow.
do_exit
sched_autogroup_exit_task
sched_move_task
dequeue_task
sched_change_group
A.sched_task_group = sched_get_task_group (=cpu_cgroup0)
enqueue_task
Performance results:
===========================
1. env
cpu: bogomips=4600.00
kernel: 6.3.0-rc3
cpu_cgroup: 6:cpu,cpuacct:/user.slice
2. cmds
do_exit script:
```
for i in {0..10000}; do
sleep 0 &
done
wait
```
Run the above script, then use the following bpftrace cmd to get
the cost of sched_move_task:
bpftrace -e 'k:sched_move_task { @ts[tid] = nsecs; }
kr:sched_move_task /@ts[tid]/
{ @ns += nsecs - @ts[tid]; delete(@ts[tid]); }'
3. cost time(ns):
without patch: 43528033
with patch: 18541416
diff:-24986617 -57.4%
As the result show, the patch will save 57.4% in the scenario.
Signed-off-by: wuchi <wuchi.zero@gmail.com>
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/sched/core.c | 30 ++++++++++++++++++++++++++++--
1 file changed, 28 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a380f34789a2..1e7d6a8c3455 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10330,7 +10330,7 @@ void sched_release_group(struct task_group *tg)
spin_unlock_irqrestore(&task_group_lock, flags);
}
-static void sched_change_group(struct task_struct *tsk)
+static struct task_group *sched_get_task_group(struct task_struct *tsk)
{
struct task_group *tg;
@@ -10342,7 +10342,28 @@ static void sched_change_group(struct task_struct *tsk)
tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
struct task_group, css);
tg = autogroup_task_group(tsk, tg);
- tsk->sched_task_group = tg;
+
+ return tg;
+}
+
+static bool sched_task_group_changed(struct task_struct *tsk)
+{
+ /*
+ * Some sched_move_task calls are useless because that
+ * task_struct->sched_task_group maybe not changed (equals
+ * task_group of cpu_cgroup) when system enable autogroup.
+ * So do some checks in sched_move_task.
+ */
+#ifdef CONFIG_SCHED_AUTOGROUP
+ return sched_get_task_group(tsk) != tsk->sched_task_group;
+#else
+ return true;
+#endif /* CONFIG_SCHED_AUTOGROUP */
+}
+
+static void sched_change_group(struct task_struct *tsk)
+{
+ tsk->sched_task_group = sched_get_task_group(tsk);
#ifdef CONFIG_FAIR_GROUP_SCHED
if (tsk->sched_class->task_change_group)
@@ -10367,6 +10388,10 @@ void sched_move_task(struct task_struct *tsk)
struct rq *rq;
rq = task_rq_lock(tsk, &rf);
+
+ if (!sched_task_group_changed(tsk))
+ goto unlock;
+
update_rq_clock(rq);
running = task_current(rq, tsk);
@@ -10391,6 +10416,7 @@ void sched_move_task(struct task_struct *tsk)
resched_curr(rq);
}
+unlock:
task_rq_unlock(rq, tsk, &rf);
}
--
2.20.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] sched/core: Reduce cost of sched_move_task when config autogroup
2023-03-21 6:44 [PATCH v2] sched/core: Reduce cost of sched_move_task when config autogroup wuchi
@ 2023-03-21 9:36 ` Peter Zijlstra
2023-03-21 11:51 ` chi wu
2023-03-22 9:22 ` [tip: sched/core] " tip-bot2 for wuchi
1 sibling, 1 reply; 4+ messages in thread
From: Peter Zijlstra @ 2023-03-21 9:36 UTC (permalink / raw)
To: wuchi
Cc: mingo, juri.lelli, vincent.guittot, dietmar.eggemann, rostedt,
bsegall, mgorman, bristot, vschneid, linux-kernel
On Tue, Mar 21, 2023 at 02:44:59PM +0800, wuchi wrote:
> kernel/sched/core.c | 30 ++++++++++++++++++++++++++++--
> 1 file changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index a380f34789a2..1e7d6a8c3455 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -10330,7 +10330,7 @@ void sched_release_group(struct task_group *tg)
> spin_unlock_irqrestore(&task_group_lock, flags);
> }
>
> -static void sched_change_group(struct task_struct *tsk)
> +static struct task_group *sched_get_task_group(struct task_struct *tsk)
> {
> struct task_group *tg;
>
> @@ -10342,7 +10342,28 @@ static void sched_change_group(struct task_struct *tsk)
> tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
> struct task_group, css);
> tg = autogroup_task_group(tsk, tg);
> - tsk->sched_task_group = tg;
> +
> + return tg;
> +}
> +
> +static bool sched_task_group_changed(struct task_struct *tsk)
> +{
> + /*
> + * Some sched_move_task calls are useless because that
> + * task_struct->sched_task_group maybe not changed (equals
> + * task_group of cpu_cgroup) when system enable autogroup.
> + * So do some checks in sched_move_task.
> + */
> +#ifdef CONFIG_SCHED_AUTOGROUP
> + return sched_get_task_group(tsk) != tsk->sched_task_group;
> +#else
> + return true;
> +#endif /* CONFIG_SCHED_AUTOGROUP */
> +}
> +
> +static void sched_change_group(struct task_struct *tsk)
> +{
> + tsk->sched_task_group = sched_get_task_group(tsk);
>
> #ifdef CONFIG_FAIR_GROUP_SCHED
> if (tsk->sched_class->task_change_group)
> @@ -10367,6 +10388,10 @@ void sched_move_task(struct task_struct *tsk)
> struct rq *rq;
>
> rq = task_rq_lock(tsk, &rf);
> +
> + if (!sched_task_group_changed(tsk))
> + goto unlock;
> +
> update_rq_clock(rq);
>
> running = task_current(rq, tsk);
> @@ -10391,6 +10416,7 @@ void sched_move_task(struct task_struct *tsk)
> resched_curr(rq);
> }
>
> +unlock:
> task_rq_unlock(rq, tsk, &rf);
> }
Would you mind terribly if I change it like so?
---
Subject: sched/core: Reduce cost of sched_move_task when config autogroup
From: wuchi <wuchi.zero@gmail.com>
Date: Tue, 21 Mar 2023 14:44:59 +0800
From: wuchi <wuchi.zero@gmail.com>
Some sched_move_task calls are useless because that
task_struct->sched_task_group maybe not changed (equals task_group
of cpu_cgroup) when system enable autogroup. So do some checks in
sched_move_task.
sched_move_task eg:
task A belongs to cpu_cgroup0 and autogroup0, it will always belong
to cpu_cgroup0 when do_exit. So there is no need to do {de|en}queue.
The call graph is as follow.
do_exit
sched_autogroup_exit_task
sched_move_task
dequeue_task
sched_change_group
A.sched_task_group = sched_get_task_group (=cpu_cgroup0)
enqueue_task
Performance results:
===========================
1. env
cpu: bogomips=4600.00
kernel: 6.3.0-rc3
cpu_cgroup: 6:cpu,cpuacct:/user.slice
2. cmds
do_exit script:
for i in {0..10000}; do
sleep 0 &
done
wait
Run the above script, then use the following bpftrace cmd to get
the cost of sched_move_task:
bpftrace -e 'k:sched_move_task { @ts[tid] = nsecs; }
kr:sched_move_task /@ts[tid]/
{ @ns += nsecs - @ts[tid]; delete(@ts[tid]); }'
3. cost time(ns):
without patch: 43528033
with patch: 18541416
diff:-24986617 -57.4%
As the result show, the patch will save 57.4% in the scenario.
Signed-off-by: wuchi <wuchi.zero@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230321064459.39421-1-wuchi.zero@gmail.com
---
kernel/sched/core.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10351,7 +10351,7 @@ void sched_release_group(struct task_gro
spin_unlock_irqrestore(&task_group_lock, flags);
}
-static void sched_change_group(struct task_struct *tsk)
+static struct task_group *sched_get_task_group(struct task_struct *tsk)
{
struct task_group *tg;
@@ -10363,7 +10363,13 @@ static void sched_change_group(struct ta
tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
struct task_group, css);
tg = autogroup_task_group(tsk, tg);
- tsk->sched_task_group = tg;
+
+ return tg;
+}
+
+static void sched_change_group(struct task_struct *tsk, struct task_group *group)
+{
+ tsk->sched_task_group = group;
#ifdef CONFIG_FAIR_GROUP_SCHED
if (tsk->sched_class->task_change_group)
@@ -10384,10 +10390,19 @@ void sched_move_task(struct task_struct
{
int queued, running, queue_flags =
DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
+ struct task_group *group;
struct rq_flags rf;
struct rq *rq;
rq = task_rq_lock(tsk, &rf);
+ /*
+ * Esp. with SCHED_AUTOGROUP enabled it is possible to get superfluous
+ * group changes.
+ */
+ group = sched_get_task_group(tsk);
+ if (group == tsk->sched_task_group)
+ goto unlock;
+
update_rq_clock(rq);
running = task_current(rq, tsk);
@@ -10398,7 +10413,7 @@ void sched_move_task(struct task_struct
if (running)
put_prev_task(rq, tsk);
- sched_change_group(tsk);
+ sched_change_group(tsk, group);
if (queued)
enqueue_task(rq, tsk, queue_flags);
@@ -10412,6 +10427,7 @@ void sched_move_task(struct task_struct
resched_curr(rq);
}
+unlock:
task_rq_unlock(rq, tsk, &rf);
}
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] sched/core: Reduce cost of sched_move_task when config autogroup
2023-03-21 9:36 ` Peter Zijlstra
@ 2023-03-21 11:51 ` chi wu
0 siblings, 0 replies; 4+ messages in thread
From: chi wu @ 2023-03-21 11:51 UTC (permalink / raw)
To: Peter Zijlstra
Cc: mingo, juri.lelli, vincent.guittot, dietmar.eggemann, rostedt,
bsegall, mgorman, bristot, vschneid, linux-kernel
Peter Zijlstra <peterz@infradead.org> 于2023年3月21日周二 17:36写道:
>
> On Tue, Mar 21, 2023 at 02:44:59PM +0800, wuchi wrote:
>
> > kernel/sched/core.c | 30 ++++++++++++++++++++++++++++--
> > 1 file changed, 28 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index a380f34789a2..1e7d6a8c3455 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -10330,7 +10330,7 @@ void sched_release_group(struct task_group *tg)
> > spin_unlock_irqrestore(&task_group_lock, flags);
> > }
> >
> > -static void sched_change_group(struct task_struct *tsk)
> > +static struct task_group *sched_get_task_group(struct task_struct *tsk)
> > {
> > struct task_group *tg;
> >
> > @@ -10342,7 +10342,28 @@ static void sched_change_group(struct task_struct *tsk)
> > tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
> > struct task_group, css);
> > tg = autogroup_task_group(tsk, tg);
> > - tsk->sched_task_group = tg;
> > +
> > + return tg;
> > +}
> > +
> > +static bool sched_task_group_changed(struct task_struct *tsk)
> > +{
> > + /*
> > + * Some sched_move_task calls are useless because that
> > + * task_struct->sched_task_group maybe not changed (equals
> > + * task_group of cpu_cgroup) when system enable autogroup.
> > + * So do some checks in sched_move_task.
> > + */
> > +#ifdef CONFIG_SCHED_AUTOGROUP
> > + return sched_get_task_group(tsk) != tsk->sched_task_group;
> > +#else
> > + return true;
> > +#endif /* CONFIG_SCHED_AUTOGROUP */
> > +}
> > +
> > +static void sched_change_group(struct task_struct *tsk)
> > +{
> > + tsk->sched_task_group = sched_get_task_group(tsk);
> >
> > #ifdef CONFIG_FAIR_GROUP_SCHED
> > if (tsk->sched_class->task_change_group)
> > @@ -10367,6 +10388,10 @@ void sched_move_task(struct task_struct *tsk)
> > struct rq *rq;
> >
> > rq = task_rq_lock(tsk, &rf);
> > +
> > + if (!sched_task_group_changed(tsk))
> > + goto unlock;
> > +
> > update_rq_clock(rq);
> >
> > running = task_current(rq, tsk);
> > @@ -10391,6 +10416,7 @@ void sched_move_task(struct task_struct *tsk)
> > resched_curr(rq);
> > }
> >
> > +unlock:
> > task_rq_unlock(rq, tsk, &rf);
> > }
>
> Would you mind terribly if I change it like so?
>
> ---
> Subject: sched/core: Reduce cost of sched_move_task when config autogroup
> From: wuchi <wuchi.zero@gmail.com>
> Date: Tue, 21 Mar 2023 14:44:59 +0800
>
> From: wuchi <wuchi.zero@gmail.com>
>
> Some sched_move_task calls are useless because that
> task_struct->sched_task_group maybe not changed (equals task_group
> of cpu_cgroup) when system enable autogroup. So do some checks in
> sched_move_task.
>
> sched_move_task eg:
> task A belongs to cpu_cgroup0 and autogroup0, it will always belong
> to cpu_cgroup0 when do_exit. So there is no need to do {de|en}queue.
> The call graph is as follow.
>
> do_exit
> sched_autogroup_exit_task
> sched_move_task
> dequeue_task
> sched_change_group
> A.sched_task_group = sched_get_task_group (=cpu_cgroup0)
> enqueue_task
>
> Performance results:
> ===========================
> 1. env
> cpu: bogomips=4600.00
> kernel: 6.3.0-rc3
> cpu_cgroup: 6:cpu,cpuacct:/user.slice
>
> 2. cmds
> do_exit script:
>
> for i in {0..10000}; do
> sleep 0 &
> done
> wait
>
> Run the above script, then use the following bpftrace cmd to get
> the cost of sched_move_task:
>
> bpftrace -e 'k:sched_move_task { @ts[tid] = nsecs; }
> kr:sched_move_task /@ts[tid]/
> { @ns += nsecs - @ts[tid]; delete(@ts[tid]); }'
>
> 3. cost time(ns):
> without patch: 43528033
> with patch: 18541416
> diff:-24986617 -57.4%
>
> As the result show, the patch will save 57.4% in the scenario.
>
> Signed-off-by: wuchi <wuchi.zero@gmail.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Link: https://lkml.kernel.org/r/20230321064459.39421-1-wuchi.zero@gmail.com
> ---
> kernel/sched/core.c | 22 +++++++++++++++++++---
> 1 file changed, 19 insertions(+), 3 deletions(-)
>
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -10351,7 +10351,7 @@ void sched_release_group(struct task_gro
> spin_unlock_irqrestore(&task_group_lock, flags);
> }
>
> -static void sched_change_group(struct task_struct *tsk)
> +static struct task_group *sched_get_task_group(struct task_struct *tsk)
> {
> struct task_group *tg;
>
> @@ -10363,7 +10363,13 @@ static void sched_change_group(struct ta
> tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
> struct task_group, css);
> tg = autogroup_task_group(tsk, tg);
> - tsk->sched_task_group = tg;
> +
> + return tg;
> +}
> +
> +static void sched_change_group(struct task_struct *tsk, struct task_group *group)
> +{
> + tsk->sched_task_group = group;
>
> #ifdef CONFIG_FAIR_GROUP_SCHED
> if (tsk->sched_class->task_change_group)
> @@ -10384,10 +10390,19 @@ void sched_move_task(struct task_struct
> {
> int queued, running, queue_flags =
> DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
> + struct task_group *group;
> struct rq_flags rf;
> struct rq *rq;
>
> rq = task_rq_lock(tsk, &rf);
> + /*
> + * Esp. with SCHED_AUTOGROUP enabled it is possible to get superfluous
> + * group changes.
> + */
> + group = sched_get_task_group(tsk);
> + if (group == tsk->sched_task_group)
> + goto unlock;
> +
> update_rq_clock(rq);
>
> running = task_current(rq, tsk);
> @@ -10398,7 +10413,7 @@ void sched_move_task(struct task_struct
> if (running)
> put_prev_task(rq, tsk);
>
> - sched_change_group(tsk);
> + sched_change_group(tsk, group);
>
> if (queued)
> enqueue_task(rq, tsk, queue_flags);
> @@ -10412,6 +10427,7 @@ void sched_move_task(struct task_struct
> resched_curr(rq);
> }
>
> +unlock:
> task_rq_unlock(rq, tsk, &rf);
> }
>
It‘s more efficient and concise, I learn more from the code. Thanks!
^ permalink raw reply [flat|nested] 4+ messages in thread
* [tip: sched/core] sched/core: Reduce cost of sched_move_task when config autogroup
2023-03-21 6:44 [PATCH v2] sched/core: Reduce cost of sched_move_task when config autogroup wuchi
2023-03-21 9:36 ` Peter Zijlstra
@ 2023-03-22 9:22 ` tip-bot2 for wuchi
1 sibling, 0 replies; 4+ messages in thread
From: tip-bot2 for wuchi @ 2023-03-22 9:22 UTC (permalink / raw)
To: linux-tip-commits; +Cc: wuchi, Peter Zijlstra (Intel), x86, linux-kernel
The following commit has been merged into the sched/core branch of tip:
Commit-ID: eff6c8ce8d4d7faef75f66614dd20bb50595d261
Gitweb: https://git.kernel.org/tip/eff6c8ce8d4d7faef75f66614dd20bb50595d261
Author: wuchi <wuchi.zero@gmail.com>
AuthorDate: Tue, 21 Mar 2023 14:44:59 +08:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 22 Mar 2023 10:10:58 +01:00
sched/core: Reduce cost of sched_move_task when config autogroup
Some sched_move_task calls are useless because that
task_struct->sched_task_group maybe not changed (equals task_group
of cpu_cgroup) when system enable autogroup. So do some checks in
sched_move_task.
sched_move_task eg:
task A belongs to cpu_cgroup0 and autogroup0, it will always belong
to cpu_cgroup0 when do_exit. So there is no need to do {de|en}queue.
The call graph is as follow.
do_exit
sched_autogroup_exit_task
sched_move_task
dequeue_task
sched_change_group
A.sched_task_group = sched_get_task_group (=cpu_cgroup0)
enqueue_task
Performance results:
===========================
1. env
cpu: bogomips=4600.00
kernel: 6.3.0-rc3
cpu_cgroup: 6:cpu,cpuacct:/user.slice
2. cmds
do_exit script:
for i in {0..10000}; do
sleep 0 &
done
wait
Run the above script, then use the following bpftrace cmd to get
the cost of sched_move_task:
bpftrace -e 'k:sched_move_task { @ts[tid] = nsecs; }
kr:sched_move_task /@ts[tid]/
{ @ns += nsecs - @ts[tid]; delete(@ts[tid]); }'
3. cost time(ns):
without patch: 43528033
with patch: 18541416
diff:-24986617 -57.4%
As the result show, the patch will save 57.4% in the scenario.
Signed-off-by: wuchi <wuchi.zero@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230321064459.39421-1-wuchi.zero@gmail.com
---
kernel/sched/core.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9140a33..5ddd961 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10351,7 +10351,7 @@ void sched_release_group(struct task_group *tg)
spin_unlock_irqrestore(&task_group_lock, flags);
}
-static void sched_change_group(struct task_struct *tsk)
+static struct task_group *sched_get_task_group(struct task_struct *tsk)
{
struct task_group *tg;
@@ -10363,7 +10363,13 @@ static void sched_change_group(struct task_struct *tsk)
tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
struct task_group, css);
tg = autogroup_task_group(tsk, tg);
- tsk->sched_task_group = tg;
+
+ return tg;
+}
+
+static void sched_change_group(struct task_struct *tsk, struct task_group *group)
+{
+ tsk->sched_task_group = group;
#ifdef CONFIG_FAIR_GROUP_SCHED
if (tsk->sched_class->task_change_group)
@@ -10384,10 +10390,19 @@ void sched_move_task(struct task_struct *tsk)
{
int queued, running, queue_flags =
DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
+ struct task_group *group;
struct rq_flags rf;
struct rq *rq;
rq = task_rq_lock(tsk, &rf);
+ /*
+ * Esp. with SCHED_AUTOGROUP enabled it is possible to get superfluous
+ * group changes.
+ */
+ group = sched_get_task_group(tsk);
+ if (group == tsk->sched_task_group)
+ goto unlock;
+
update_rq_clock(rq);
running = task_current(rq, tsk);
@@ -10398,7 +10413,7 @@ void sched_move_task(struct task_struct *tsk)
if (running)
put_prev_task(rq, tsk);
- sched_change_group(tsk);
+ sched_change_group(tsk, group);
if (queued)
enqueue_task(rq, tsk, queue_flags);
@@ -10412,6 +10427,7 @@ void sched_move_task(struct task_struct *tsk)
resched_curr(rq);
}
+unlock:
task_rq_unlock(rq, tsk, &rf);
}
^ permalink raw reply related [flat|nested] 4+ messages in thread
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2023-03-21 6:44 [PATCH v2] sched/core: Reduce cost of sched_move_task when config autogroup wuchi
2023-03-21 9:36 ` Peter Zijlstra
2023-03-21 11:51 ` chi wu
2023-03-22 9:22 ` [tip: sched/core] " tip-bot2 for wuchi
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