On 2019/6/6 AM 4:06, [email protected] wrote:
> When a cfs_rq sleeps and returns its quota, we delay for 5ms before
> waking any throttled cfs_rqs to coalesce with other cfs_rqs going to
> sleep, as this has has to be done outside of the rq lock we hold.
two "has".
>
> The current code waits for 5ms without any sleeps, instead of waiting
> for 5ms from the first sleep, which can delay the unthrottle more than
> we want. Switch this around so that we can't push this forward forever.
>
> This requires an extra flag rather than using hrtimer_active, since we
> need to start a new timer if the current one is in the process of
> finishing.
>
> Signed-off-by: Ben Segall <[email protected]>
> ---
We've also suffered from this performance issue recently:
Reviewed-by: Xunlei Pang <[email protected]>
> kernel/sched/fair.c | 7 +++++++
> kernel/sched/sched.h | 1 +
> 2 files changed, 8 insertions(+)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 8213ff6e365d..2ead252cfa32 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4729,6 +4729,11 @@ static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
> if (runtime_refresh_within(cfs_b, min_left))
> return;
>
> + /* don't push forwards an existing deferred unthrottle */
> + if (cfs_b->slack_started)
> + return;
> + cfs_b->slack_started = true;
> +
> hrtimer_start(&cfs_b->slack_timer,
> ns_to_ktime(cfs_bandwidth_slack_period),
> HRTIMER_MODE_REL);
> @@ -4782,6 +4787,7 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
>
> /* confirm we're still not at a refresh boundary */
> raw_spin_lock_irqsave(&cfs_b->lock, flags);
> + cfs_b->slack_started = false;
> if (cfs_b->distribute_running) {
> raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
> return;
> @@ -4920,6 +4926,7 @@ void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
> hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> cfs_b->slack_timer.function = sched_cfs_slack_timer;
> cfs_b->distribute_running = 0;
> + cfs_b->slack_started = false;
> }
>
> static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index efa686eeff26..60219acda94b 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -356,6 +356,7 @@ struct cfs_bandwidth {
> u64 throttled_time;
>
> bool distribute_running;
> + bool slack_started;
> #endif
> };
>
>
When a cfs_rq sleeps and returns its quota, we delay for 5ms before
waking any throttled cfs_rqs to coalesce with other cfs_rqs going to
sleep, as this has to be done outside of the rq lock we hold.
The current code waits for 5ms without any sleeps, instead of waiting
for 5ms from the first sleep, which can delay the unthrottle more than
we want. Switch this around so that we can't push this forward forever.
This requires an extra flag rather than using hrtimer_active, since we
need to start a new timer if the current one is in the process of
finishing.
Signed-off-by: Ben Segall <[email protected]>
Reviewed-by: Xunlei Pang <[email protected]>
---
kernel/sched/fair.c | 7 +++++++
kernel/sched/sched.h | 1 +
2 files changed, 8 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8213ff6e365d..2ead252cfa32 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4729,6 +4729,11 @@ static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
if (runtime_refresh_within(cfs_b, min_left))
return;
+ /* don't push forwards an existing deferred unthrottle */
+ if (cfs_b->slack_started)
+ return;
+ cfs_b->slack_started = true;
+
hrtimer_start(&cfs_b->slack_timer,
ns_to_ktime(cfs_bandwidth_slack_period),
HRTIMER_MODE_REL);
@@ -4782,6 +4787,7 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
/* confirm we're still not at a refresh boundary */
raw_spin_lock_irqsave(&cfs_b->lock, flags);
+ cfs_b->slack_started = false;
if (cfs_b->distribute_running) {
raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
return;
@@ -4920,6 +4926,7 @@ void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
cfs_b->slack_timer.function = sched_cfs_slack_timer;
cfs_b->distribute_running = 0;
+ cfs_b->slack_started = false;
}
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index efa686eeff26..60219acda94b 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -356,6 +356,7 @@ struct cfs_bandwidth {
u64 throttled_time;
bool distribute_running;
+ bool slack_started;
#endif
};
--
2.22.0.rc1.257.g3120a18244-goog
On Thu, Jun 06, 2019 at 10:21:01AM -0700 [email protected] wrote:
> When a cfs_rq sleeps and returns its quota, we delay for 5ms before
> waking any throttled cfs_rqs to coalesce with other cfs_rqs going to
> sleep, as this has to be done outside of the rq lock we hold.
>
> The current code waits for 5ms without any sleeps, instead of waiting
> for 5ms from the first sleep, which can delay the unthrottle more than
> we want. Switch this around so that we can't push this forward forever.
>
> This requires an extra flag rather than using hrtimer_active, since we
> need to start a new timer if the current one is in the process of
> finishing.
>
> Signed-off-by: Ben Segall <[email protected]>
> Reviewed-by: Xunlei Pang <[email protected]>
> ---
> kernel/sched/fair.c | 7 +++++++
> kernel/sched/sched.h | 1 +
> 2 files changed, 8 insertions(+)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 8213ff6e365d..2ead252cfa32 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4729,6 +4729,11 @@ static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
> if (runtime_refresh_within(cfs_b, min_left))
> return;
>
> + /* don't push forwards an existing deferred unthrottle */
> + if (cfs_b->slack_started)
> + return;
> + cfs_b->slack_started = true;
> +
> hrtimer_start(&cfs_b->slack_timer,
> ns_to_ktime(cfs_bandwidth_slack_period),
> HRTIMER_MODE_REL);
> @@ -4782,6 +4787,7 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
>
> /* confirm we're still not at a refresh boundary */
> raw_spin_lock_irqsave(&cfs_b->lock, flags);
> + cfs_b->slack_started = false;
> if (cfs_b->distribute_running) {
> raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
> return;
> @@ -4920,6 +4926,7 @@ void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
> hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> cfs_b->slack_timer.function = sched_cfs_slack_timer;
> cfs_b->distribute_running = 0;
> + cfs_b->slack_started = false;
> }
>
> static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index efa686eeff26..60219acda94b 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -356,6 +356,7 @@ struct cfs_bandwidth {
> u64 throttled_time;
>
> bool distribute_running;
> + bool slack_started;
> #endif
> };
>
> --
> 2.22.0.rc1.257.g3120a18244-goog
>
I think this looks good. I like not delaying that further even if it
does not fix Dave's use case.
It does make it glaring that I should have used false/true for setting
distribute_running though :)
Acked-by: Phil Auld <[email protected]>
--
On Tue, Jun 11, 2019 at 09:04:17AM -0400, Phil Auld wrote:
> On Thu, Jun 06, 2019 at 10:21:01AM -0700 [email protected] wrote:
> > When a cfs_rq sleeps and returns its quota, we delay for 5ms before
> > waking any throttled cfs_rqs to coalesce with other cfs_rqs going to
> > sleep, as this has to be done outside of the rq lock we hold.
> >
> > The current code waits for 5ms without any sleeps, instead of waiting
> > for 5ms from the first sleep, which can delay the unthrottle more than
> > we want. Switch this around so that we can't push this forward forever.
> >
> > This requires an extra flag rather than using hrtimer_active, since we
> > need to start a new timer if the current one is in the process of
> > finishing.
> >
> > Signed-off-by: Ben Segall <[email protected]>
> > Reviewed-by: Xunlei Pang <[email protected]>
> > ---
> > kernel/sched/fair.c | 7 +++++++
> > kernel/sched/sched.h | 1 +
> > 2 files changed, 8 insertions(+)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 8213ff6e365d..2ead252cfa32 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -4729,6 +4729,11 @@ static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
> > if (runtime_refresh_within(cfs_b, min_left))
> > return;
> >
> > + /* don't push forwards an existing deferred unthrottle */
> > + if (cfs_b->slack_started)
> > + return;
> > + cfs_b->slack_started = true;
> > +
> > hrtimer_start(&cfs_b->slack_timer,
> > ns_to_ktime(cfs_bandwidth_slack_period),
> > HRTIMER_MODE_REL);
> > @@ -4782,6 +4787,7 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
> >
> > /* confirm we're still not at a refresh boundary */
> > raw_spin_lock_irqsave(&cfs_b->lock, flags);
> > + cfs_b->slack_started = false;
> > if (cfs_b->distribute_running) {
> > raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
> > return;
> > @@ -4920,6 +4926,7 @@ void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
> > hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> > cfs_b->slack_timer.function = sched_cfs_slack_timer;
> > cfs_b->distribute_running = 0;
> > + cfs_b->slack_started = false;
> > }
> >
> > static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
> > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> > index efa686eeff26..60219acda94b 100644
> > --- a/kernel/sched/sched.h
> > +++ b/kernel/sched/sched.h
> > @@ -356,6 +356,7 @@ struct cfs_bandwidth {
> > u64 throttled_time;
> >
> > bool distribute_running;
> > + bool slack_started;
> > #endif
> > };
> >
> > --
> > 2.22.0.rc1.257.g3120a18244-goog
> >
>
> I think this looks good. I like not delaying that further even if it
> does not fix Dave's use case.
>
> It does make it glaring that I should have used false/true for setting
> distribute_running though :)
>
>
> Acked-by: Phil Auld <[email protected]>
Thanks!
Should this patch have a Fixes: tag?
On Thu, Jun 06, 2019 at 10:21:01AM -0700, [email protected] wrote:
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index efa686eeff26..60219acda94b 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -356,6 +356,7 @@ struct cfs_bandwidth {
> u64 throttled_time;
>
> bool distribute_running;
> + bool slack_started;
> #endif
> };
I'm thinking we can this instead? afaict both idle and period_active are
already effecitively booleans and don't need the full 16 bits.
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -338,8 +338,10 @@ struct cfs_bandwidth {
u64 runtime_expires;
int expires_seq;
- short idle;
- short period_active;
+ u8 idle;
+ u8 period_active;
+ u8 distribute_running;
+ u8 slack_started;
struct hrtimer period_timer;
struct hrtimer slack_timer;
struct list_head throttled_cfs_rq;
@@ -348,9 +350,6 @@ struct cfs_bandwidth {
int nr_periods;
int nr_throttled;
u64 throttled_time;
-
- bool distribute_running;
- bool slack_started;
#endif
};
On Tue, Jun 11, 2019 at 03:53:25PM +0200 Peter Zijlstra wrote:
> On Thu, Jun 06, 2019 at 10:21:01AM -0700, [email protected] wrote:
> > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> > index efa686eeff26..60219acda94b 100644
> > --- a/kernel/sched/sched.h
> > +++ b/kernel/sched/sched.h
> > @@ -356,6 +356,7 @@ struct cfs_bandwidth {
> > u64 throttled_time;
> >
> > bool distribute_running;
> > + bool slack_started;
> > #endif
> > };
>
> I'm thinking we can this instead? afaict both idle and period_active are
> already effecitively booleans and don't need the full 16 bits.
>
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -338,8 +338,10 @@ struct cfs_bandwidth {
> u64 runtime_expires;
> int expires_seq;
>
> - short idle;
> - short period_active;
> + u8 idle;
> + u8 period_active;
> + u8 distribute_running;
> + u8 slack_started;
> struct hrtimer period_timer;
> struct hrtimer slack_timer;
> struct list_head throttled_cfs_rq;
> @@ -348,9 +350,6 @@ struct cfs_bandwidth {
> int nr_periods;
> int nr_throttled;
> u64 throttled_time;
> -
> - bool distribute_running;
> - bool slack_started;
> #endif
> };
>
That looks reasonable to me.
Out of curiosity, why not bool? Is sizeof bool architecture dependent?
--
On Tue, Jun 11, 2019 at 10:12:19AM -0400, Phil Auld wrote:
> That looks reasonable to me.
>
> Out of curiosity, why not bool? Is sizeof bool architecture dependent?
Yeah, sizeof(_Bool) is unspecified and depends on ABI. It is mostly 1,
but there are known cases where it is 4.
On Tue, Jun 11, 2019 at 04:24:43PM +0200 Peter Zijlstra wrote:
> On Tue, Jun 11, 2019 at 10:12:19AM -0400, Phil Auld wrote:
>
> > That looks reasonable to me.
> >
> > Out of curiosity, why not bool? Is sizeof bool architecture dependent?
>
> Yeah, sizeof(_Bool) is unspecified and depends on ABI. It is mostly 1,
> but there are known cases where it is 4.
Makes sense. Thanks!
--
Peter Zijlstra <[email protected]> writes:
> On Thu, Jun 06, 2019 at 10:21:01AM -0700, [email protected] wrote:
>> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
>> index efa686eeff26..60219acda94b 100644
>> --- a/kernel/sched/sched.h
>> +++ b/kernel/sched/sched.h
>> @@ -356,6 +356,7 @@ struct cfs_bandwidth {
>> u64 throttled_time;
>>
>> bool distribute_running;
>> + bool slack_started;
>> #endif
>> };
>
> I'm thinking we can this instead? afaict both idle and period_active are
> already effecitively booleans and don't need the full 16 bits.
>
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -338,8 +338,10 @@ struct cfs_bandwidth {
> u64 runtime_expires;
> int expires_seq;
>
> - short idle;
> - short period_active;
> + u8 idle;
> + u8 period_active;
> + u8 distribute_running;
> + u8 slack_started;
> struct hrtimer period_timer;
> struct hrtimer slack_timer;
> struct list_head throttled_cfs_rq;
> @@ -348,9 +350,6 @@ struct cfs_bandwidth {
> int nr_periods;
> int nr_throttled;
> u64 throttled_time;
> -
> - bool distribute_running;
> - bool slack_started;
> #endif
> };
>
Yeah, that makes sense to me, should I spin up another version of the
patch doing this too or do you have it from here?
Commit-ID: 66567fcbaecac455caa1b13643155d686b51ce63
Gitweb: https://git.kernel.org/tip/66567fcbaecac455caa1b13643155d686b51ce63
Author: [email protected] <[email protected]>
AuthorDate: Thu, 6 Jun 2019 10:21:01 -0700
Committer: Ingo Molnar <[email protected]>
CommitDate: Mon, 17 Jun 2019 12:16:01 +0200
sched/fair: Don't push cfs_bandwith slack timers forward
When a cfs_rq sleeps and returns its quota, we delay for 5ms before
waking any throttled cfs_rqs to coalesce with other cfs_rqs going to
sleep, as this has to be done outside of the rq lock we hold.
The current code waits for 5ms without any sleeps, instead of waiting
for 5ms from the first sleep, which can delay the unthrottle more than
we want. Switch this around so that we can't push this forward forever.
This requires an extra flag rather than using hrtimer_active, since we
need to start a new timer if the current one is in the process of
finishing.
Signed-off-by: Ben Segall <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Xunlei Pang <[email protected]>
Acked-by: Phil Auld <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/sched/fair.c | 7 +++++++
kernel/sched/sched.h | 8 ++++----
2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 4c8f45ed093c..3c11dcdedcbc 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4729,6 +4729,11 @@ static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
if (runtime_refresh_within(cfs_b, min_left))
return;
+ /* don't push forwards an existing deferred unthrottle */
+ if (cfs_b->slack_started)
+ return;
+ cfs_b->slack_started = true;
+
hrtimer_start(&cfs_b->slack_timer,
ns_to_ktime(cfs_bandwidth_slack_period),
HRTIMER_MODE_REL);
@@ -4782,6 +4787,7 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
/* confirm we're still not at a refresh boundary */
raw_spin_lock_irqsave(&cfs_b->lock, flags);
+ cfs_b->slack_started = false;
if (cfs_b->distribute_running) {
raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
return;
@@ -4945,6 +4951,7 @@ void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
cfs_b->slack_timer.function = sched_cfs_slack_timer;
cfs_b->distribute_running = 0;
+ cfs_b->slack_started = false;
}
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 607859a18b2a..b08dee29ef5e 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -338,8 +338,10 @@ struct cfs_bandwidth {
u64 runtime_expires;
int expires_seq;
- short idle;
- short period_active;
+ u8 idle;
+ u8 period_active;
+ u8 distribute_running;
+ u8 slack_started;
struct hrtimer period_timer;
struct hrtimer slack_timer;
struct list_head throttled_cfs_rq;
@@ -348,8 +350,6 @@ struct cfs_bandwidth {
int nr_periods;
int nr_throttled;
u64 throttled_time;
-
- bool distribute_running;
#endif
};