[PATCH v2] sched/pelt: Keep UTIL_AVG_UNCHANGED flag in sync when calculating last_enqueued_diff

[PATCH v2] sched/pelt: Keep UTIL_AVG_UNCHANGED flag in sync when calculating last_enqueued_diff

[Xuewen Yan]

From: Xuewen Yan <xuewen.yan@unisoc.com>

Last_enqueued_diff's meaning: "diff = util_est.enqueued(p) - task_util(p)".
When calculating last_enqueued_diff, we add UTIL_AVG_UNCHANGED flag, which
is the LSB, for task_util, but don't add the flag for util_est.enqueued.
However the enqueued's flag had been cleared when the task util changed.
As a result, we add +1 to the diff, this is therefore reducing slightly
UTIL_EST_MARGIN.

Add the flag for util_est.enqueued to have a accurate computation.

Fixes: b89997aa88f0b sched/pelt: Fix task util_est update filtering

Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e5e457fa9dc8..94d77b4fa601 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3996,7 +3996,7 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
 	if (ue.enqueued & UTIL_AVG_UNCHANGED)
 		return;
 
-	last_enqueued_diff = ue.enqueued;
+	last_enqueued_diff = (ue.enqueued | UTIL_AVG_UNCHANGED);
 
 	/*
 	 * Reset EWMA on utilization increases, the moving average is used only
-- 
2.29.0

Re: [PATCH v2] sched/pelt: Keep UTIL_AVG_UNCHANGED flag in sync when calculating last_enqueued_diff

[Vincent Donnefort]

On Fri, May 07, 2021 at 07:20:31PM +0800, Xuewen Yan wrote:
> From: Xuewen Yan <xuewen.yan@unisoc.com>
> 
> Last_enqueued_diff's meaning: "diff = util_est.enqueued(p) - task_util(p)".
> When calculating last_enqueued_diff, we add UTIL_AVG_UNCHANGED flag, which
> is the LSB, for task_util, but don't add the flag for util_est.enqueued.
> However the enqueued's flag had been cleared when the task util changed.
> As a result, we add +1 to the diff, this is therefore reducing slightly
> UTIL_EST_MARGIN.

Unless I miss something it actually depends on the situation, doesn't it?

if ue.enqueued > task_util(), we remove 1 from the diff => UTIL_EST_MARGIN + 1

if ue.enqueued < task_util(), we add 1 to the diff => UTIL_EST_MARGIN -1

> 
> Add the flag for util_est.enqueued to have a accurate computation.
> 
> Fixes: b89997aa88f0b sched/pelt: Fix task util_est update filtering
> 
> Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
> ---
>  kernel/sched/fair.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index e5e457fa9dc8..94d77b4fa601 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3996,7 +3996,7 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
>  	if (ue.enqueued & UTIL_AVG_UNCHANGED)
>  		return;
>  
> -	last_enqueued_diff = ue.enqueued;
> +	last_enqueued_diff = (ue.enqueued | UTIL_AVG_UNCHANGED);
>  
>  	/*
>  	 * Reset EWMA on utilization increases, the moving average is used only
> -- 
> 2.29.0
>

Re: [PATCH v2] sched/pelt: Keep UTIL_AVG_UNCHANGED flag in sync when calculating last_enqueued_diff

[Dietmar Eggemann]

On 07/05/2021 14:35, Vincent Donnefort wrote:
> On Fri, May 07, 2021 at 07:20:31PM +0800, Xuewen Yan wrote:
>> From: Xuewen Yan <xuewen.yan@unisoc.com>
>>
>> Last_enqueued_diff's meaning: "diff = util_est.enqueued(p) - task_util(p)".
>> When calculating last_enqueued_diff, we add UTIL_AVG_UNCHANGED flag, which
>> is the LSB, for task_util, but don't add the flag for util_est.enqueued.
>> However the enqueued's flag had been cleared when the task util changed.
>> As a result, we add +1 to the diff, this is therefore reducing slightly
>> UTIL_EST_MARGIN.
> 
> Unless I miss something it actually depends on the situation, doesn't it?
> 
> if ue.enqueued > task_util(), we remove 1 from the diff => UTIL_EST_MARGIN + 1
> 
> if ue.enqueued < task_util(), we add 1 to the diff => UTIL_EST_MARGIN -1

I get:

ue.enqueued & UTIL_AVG_UNCHANGED = 0

last_enqueued_diff = ue.enqueued_old                    -  ue.enqueued_new

last_enqueued_diff = (ue.enqueued | UTIL_AVG_UNCHANGED) - (task_util(p) | UTIL_AVG_UNCHANGED)

                                   ^^^^^^^^^^^^^^^^^^^^
                                   added by patch


ue.enqueued_old didn't have the flag, otherwise would return earlier

task_util(p) could have the LSB set but we just set it to make sure it's set

So last_enqueued_diff is 1 larger.

But UTIL_EST_MARGIN stays `SCHED_CAPACITY_SCALE / 100` ?

Did I miss something here?

>>
>> Add the flag for util_est.enqueued to have a accurate computation.
>>
>> Fixes: b89997aa88f0b sched/pelt: Fix task util_est update filtering
>>
>> Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
>> ---
>>  kernel/sched/fair.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index e5e457fa9dc8..94d77b4fa601 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -3996,7 +3996,7 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
>>  	if (ue.enqueued & UTIL_AVG_UNCHANGED)
>>  		return;
>>  
>> -	last_enqueued_diff = ue.enqueued;
>> +	last_enqueued_diff = (ue.enqueued | UTIL_AVG_UNCHANGED);
>>  
>>  	/*
>>  	 * Reset EWMA on utilization increases, the moving average is used only
>> -- 
>> 2.29.0
>>

Re: [PATCH v2] sched/pelt: Keep UTIL_AVG_UNCHANGED flag in sync when calculating last_enqueued_diff

[Vincent Donnefort]

On Fri, May 07, 2021 at 03:36:47PM +0200, Dietmar Eggemann wrote:
> On 07/05/2021 14:35, Vincent Donnefort wrote:
> > On Fri, May 07, 2021 at 07:20:31PM +0800, Xuewen Yan wrote:
> >> From: Xuewen Yan <xuewen.yan@unisoc.com>
> >>
> >> Last_enqueued_diff's meaning: "diff = util_est.enqueued(p) - task_util(p)".
> >> When calculating last_enqueued_diff, we add UTIL_AVG_UNCHANGED flag, which
> >> is the LSB, for task_util, but don't add the flag for util_est.enqueued.
> >> However the enqueued's flag had been cleared when the task util changed.
> >> As a result, we add +1 to the diff, this is therefore reducing slightly
> >> UTIL_EST_MARGIN.
> > 
> > Unless I miss something it actually depends on the situation, doesn't it?
> > 
> > if ue.enqueued > task_util(), we remove 1 from the diff => UTIL_EST_MARGIN + 1
> > 
> > if ue.enqueued < task_util(), we add 1 to the diff => UTIL_EST_MARGIN -1
> 
> I get:
> 
> ue.enqueued & UTIL_AVG_UNCHANGED = 0
> 
> last_enqueued_diff = ue.enqueued_old                    -  ue.enqueued_new
> 
> last_enqueued_diff = (ue.enqueued | UTIL_AVG_UNCHANGED) - (task_util(p) | UTIL_AVG_UNCHANGED)
> 
>                                    ^^^^^^^^^^^^^^^^^^^^
>                                    added by patch
> 
> 
> ue.enqueued_old didn't have the flag, otherwise would return earlier
> 
> task_util(p) could have the LSB set but we just set it to make sure it's set
> 
> So last_enqueued_diff is 1 larger.

But we take the abs() of last_enqueued_diff.

If we consider the following examples:

   enqueued_old = 5, enqueued_new = 9
   diff = 5 - (9 + 1) => 5 - 10 => -5

   enqueued_old = 9, enqueued_new = 5
   diff = 9 - (5 + 1) => 9 - 6 => 3

In both cases the delta is supposed to be 4. But in the first case we end-up
with 5. In the second, we end-up with 3. That's why I meant the effect on the
diff depends on who's greater, ue.enqueued or task_util().

> 
> But UTIL_EST_MARGIN stays `SCHED_CAPACITY_SCALE / 100` ?
> 
> Did I miss something here?

But the only purpose of the diff is the comparison against the margin. So
+/-1 in the diff ends-up being the same as doing the opposite for the margin.

All in all, the missing flag ends-up by modifying UTIL_EST_MARGIN by -1 or +1.

-- 
Vincent

Re: [PATCH v2] sched/pelt: Keep UTIL_AVG_UNCHANGED flag in sync when calculating last_enqueued_diff

[Dietmar Eggemann]

On 07/05/2021 17:38, Vincent Donnefort wrote:
> On Fri, May 07, 2021 at 03:36:47PM +0200, Dietmar Eggemann wrote:
>> On 07/05/2021 14:35, Vincent Donnefort wrote:
>>> On Fri, May 07, 2021 at 07:20:31PM +0800, Xuewen Yan wrote:
>>>> From: Xuewen Yan <xuewen.yan@unisoc.com>
>>>>
>>>> Last_enqueued_diff's meaning: "diff = util_est.enqueued(p) - task_util(p)".
>>>> When calculating last_enqueued_diff, we add UTIL_AVG_UNCHANGED flag, which
>>>> is the LSB, for task_util, but don't add the flag for util_est.enqueued.
>>>> However the enqueued's flag had been cleared when the task util changed.
>>>> As a result, we add +1 to the diff, this is therefore reducing slightly
>>>> UTIL_EST_MARGIN.
>>>
>>> Unless I miss something it actually depends on the situation, doesn't it?
>>>
>>> if ue.enqueued > task_util(), we remove 1 from the diff => UTIL_EST_MARGIN + 1
>>>
>>> if ue.enqueued < task_util(), we add 1 to the diff => UTIL_EST_MARGIN -1
>>
>> I get:
>>
>> ue.enqueued & UTIL_AVG_UNCHANGED = 0
>>
>> last_enqueued_diff = ue.enqueued_old                    -  ue.enqueued_new
>>
>> last_enqueued_diff = (ue.enqueued | UTIL_AVG_UNCHANGED) - (task_util(p) | UTIL_AVG_UNCHANGED)
>>
>>                                    ^^^^^^^^^^^^^^^^^^^^
>>                                    added by patch
>>
>>
>> ue.enqueued_old didn't have the flag, otherwise would return earlier
>>
>> task_util(p) could have the LSB set but we just set it to make sure it's set
>>
>> So last_enqueued_diff is 1 larger.
> 
> But we take the abs() of last_enqueued_diff.
> 
> If we consider the following examples:
> 
>    enqueued_old = 5, enqueued_new = 9
>    diff = 5 - (9 + 1) => 5 - 10 => -5
> 
>    enqueued_old = 9, enqueued_new = 5
>    diff = 9 - (5 + 1) => 9 - 6 => 3
> 
> In both cases the delta is supposed to be 4. But in the first case we end-up
> with 5. In the second, we end-up with 3. That's why I meant the effect on the
> diff depends on who's greater, ue.enqueued or task_util().

Ah, OK, due to the abs() in within_margin(). But util's LSB is lost due
to the flag anyway. Hence I assume e.g. enqueued_new = 9 should be
(task_util() = 8) + 1 (| flag) in the example.

OTHA, implementing UTIL_AVG_UNCHANGED as LSB and making this visible on
the util_est 'API' has other issues too. The condition
`!task_util_est(p)` can never be true in find_energy_efficient_cpu()
because of UTIL_AVG_UNCHANGED.

So why not use `UTIL_AVG_UNCHANGED = 0x80000000` and just keep its use
internal (between cfs_se_util_change() and util_est_update()), i.e. not
exporting it (via _task_util_est()) and not eclipsing util_est's LSB
value?

--->8---

From: Dietmar Eggemann <dietmar.eggemann@arm.com>
Date: Fri, 5 Feb 2021 14:48:42 +0100
Subject: [PATCH] sched/fair: Fix util_est UTIL_AVG_UNCHANGED behaviour

The util_est internal UTIL_AVG_UNCHANGED flag which is used to prevent
unnecessary util_est updates uses the LSB of util_est.enqueued. It is
exposed via _task_util_est() (and task_util_est()).

Commit 92a801e5d5b7 ("sched/fair: Mask UTIL_AVG_UNCHANGED usages")
mentions that the LSB is lost for util_est resolution but
find_energy_efficient_cpu() checks if task_util_est() returns 0 to
return prev_cpu early.

Because of _task_util_est() returning the actual util est value or'ed w/
UTIL_AVG_UNCHANGED for a dequeued task this can never be true w/
SCHED_FEAT(UTIL_EST, true).

To fix this use the MSB of util_est.enqueued instead and keep the flag
util_est internal, i.e. don't export it via _task_util_est().

MSB of unsigned int util_est.enqueued shouldn't be used for a task
since the maximal possible util_avg value for a task is 1024.

As a caveat the code behind the util_est_se trace point has to filter
UTIL_AVG_UNCHANGED to see the real util_est.enqueued value which should
be easy to do.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
---
 kernel/sched/fair.c |  5 +++--
 kernel/sched/pelt.h | 11 ++++++-----
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1d75af1ecfb4..dd30e362c3cc 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3902,7 +3902,7 @@ static inline unsigned long _task_util_est(struct task_struct *p)
 {
 	struct util_est ue = READ_ONCE(p->se.avg.util_est);
 
-	return (max(ue.ewma, ue.enqueued) | UTIL_AVG_UNCHANGED);
+	return max(ue.ewma, (ue.enqueued & ~UTIL_AVG_UNCHANGED));
 }
 
 static inline unsigned long task_util_est(struct task_struct *p)
@@ -4002,7 +4002,7 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
 	 * Reset EWMA on utilization increases, the moving average is used only
 	 * to smooth utilization decreases.
 	 */
-	ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED);
+	ue.enqueued = task_util(p);
 	if (sched_feat(UTIL_EST_FASTUP)) {
 		if (ue.ewma < ue.enqueued) {
 			ue.ewma = ue.enqueued;
@@ -4051,6 +4051,7 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
 	ue.ewma  += last_ewma_diff;
 	ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
 done:
+	ue.enqueued |= UTIL_AVG_UNCHANGED;
 	WRITE_ONCE(p->se.avg.util_est, ue);
 
 	trace_sched_util_est_se_tp(&p->se);
diff --git a/kernel/sched/pelt.h b/kernel/sched/pelt.h
index 1462846d244e..476faf61f14a 100644
--- a/kernel/sched/pelt.h
+++ b/kernel/sched/pelt.h
@@ -43,13 +43,14 @@ static inline u32 get_pelt_divider(struct sched_avg *avg)
 }
 
 /*
- * When a task is dequeued, its estimated utilization should not be update if
- * its util_avg has not been updated at least once.
+ * When a task is dequeued, its estimated utilization should not be updated if
+ * its util_avg has not been updated in the meantime.
  * This flag is used to synchronize util_avg updates with util_est updates.
- * We map this information into the LSB bit of the utilization saved at
- * dequeue time (i.e. util_est.dequeued).
+ * We map this information into the MSB bit of util_est.enqueued at dequeue
+ * time. Since max value of util_est.enqueued for a task is 1024 (PELT
+ * util_avg for a task) it is safe to use MSB here.
  */
-#define UTIL_AVG_UNCHANGED 0x1
+#define UTIL_AVG_UNCHANGED 0x80000000
 
 static inline void cfs_se_util_change(struct sched_avg *avg)
 {
-- 
2.25.1

Re: [PATCH v2] sched/pelt: Keep UTIL_AVG_UNCHANGED flag in sync when calculating last_enqueued_diff

[Vincent Donnefort]

[...]

> > 
> > But we take the abs() of last_enqueued_diff.
> > 
> > If we consider the following examples:
> > 
> >    enqueued_old = 5, enqueued_new = 9
> >    diff = 5 - (9 + 1) => 5 - 10 => -5
> > 
> >    enqueued_old = 9, enqueued_new = 5
> >    diff = 9 - (5 + 1) => 9 - 6 => 3
> > 
> > In both cases the delta is supposed to be 4. But in the first case we end-up
> > with 5. In the second, we end-up with 3. That's why I meant the effect on the
> > diff depends on who's greater, ue.enqueued or task_util().
> 
> Ah, OK, due to the abs() in within_margin(). But util's LSB is lost due
> to the flag anyway. Hence I assume e.g. enqueued_new = 9 should be
> (task_util() = 8) + 1 (| flag) in the example.

Yeah, I should have used an even number for the demonstration :-) 

> 
> OTHA, implementing UTIL_AVG_UNCHANGED as LSB and making this visible on
> the util_est 'API' has other issues too. The condition
> `!task_util_est(p)` can never be true in find_energy_efficient_cpu()
> because of UTIL_AVG_UNCHANGED.
> 
> So why not use `UTIL_AVG_UNCHANGED = 0x80000000` and just keep its use
> internal (between cfs_se_util_change() and util_est_update()), i.e. not
> exporting it (via _task_util_est()) and not eclipsing util_est's LSB
> value?

As this would be fixing two issues at once, it's probably preferable.

[...]

>  kernel/sched/fair.c |  5 +++--
>  kernel/sched/pelt.h | 11 ++++++-----
>  2 files changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 1d75af1ecfb4..dd30e362c3cc 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3902,7 +3902,7 @@ static inline unsigned long _task_util_est(struct task_struct *p)
>  {
>  	struct util_est ue = READ_ONCE(p->se.avg.util_est);
>  
> -	return (max(ue.ewma, ue.enqueued) | UTIL_AVG_UNCHANGED);
> +	return max(ue.ewma, (ue.enqueued & ~UTIL_AVG_UNCHANGED));
>  }
>  
>  static inline unsigned long task_util_est(struct task_struct *p)
> @@ -4002,7 +4002,7 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
>  	 * Reset EWMA on utilization increases, the moving average is used only
>  	 * to smooth utilization decreases.
>  	 */

Needs to be updated to add:

 	last_enqueued_diff = ue.enqueued & ~UTIL_AVG_UNCHANGED;

> -	ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED);
> +	ue.enqueued = task_util(p);
>  	if (sched_feat(UTIL_EST_FASTUP)) {
>  		if (ue.ewma < ue.enqueued) {
>  			ue.ewma = ue.enqueued;
> @@ -4051,6 +4051,7 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
>  	ue.ewma  += last_ewma_diff;
>  	ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
>  done:
> +	ue.enqueued |= UTIL_AVG_UNCHANGED;
>  	WRITE_ONCE(p->se.avg.util_est, ue);
>  
>  	trace_sched_util_est_se_tp(&p->se);
> diff --git a/kernel/sched/pelt.h b/kernel/sched/pelt.h
> index 1462846d244e..476faf61f14a 100644

Re: [PATCH v2] sched/pelt: Keep UTIL_AVG_UNCHANGED flag in sync when calculating last_enqueued_diff

[Xuewen Yan]

On Sat, May 8, 2021 at 1:14 AM Vincent Donnefort
<vincent.donnefort@arm.com> wrote:
>
> [...]
>
> > >
> > > But we take the abs() of last_enqueued_diff.
> > >
> > > If we consider the following examples:
> > >
> > >    enqueued_old = 5, enqueued_new = 9
> > >    diff = 5 - (9 + 1) => 5 - 10 => -5
> > >
> > >    enqueued_old = 9, enqueued_new = 5
> > >    diff = 9 - (5 + 1) => 9 - 6 => 3
> > >
> > > In both cases the delta is supposed to be 4. But in the first case we end-up
> > > with 5. In the second, we end-up with 3. That's why I meant the effect on the
> > > diff depends on who's greater, ue.enqueued or task_util().
> >
> > Ah, OK, due to the abs() in within_margin(). But util's LSB is lost due
> > to the flag anyway. Hence I assume e.g. enqueued_new = 9 should be
> > (task_util() = 8) + 1 (| flag) in the example.
>
> Yeah, I should have used an even number for the demonstration :-)
>
> >
> > OTHA, implementing UTIL_AVG_UNCHANGED as LSB and making this visible on
> > the util_est 'API' has other issues too. The condition
> > `!task_util_est(p)` can never be true in find_energy_efficient_cpu()
> > because of UTIL_AVG_UNCHANGED.
> >
> > So why not use `UTIL_AVG_UNCHANGED = 0x80000000` and just keep its use
> > internal (between cfs_se_util_change() and util_est_update()), i.e. not
> > exporting it (via _task_util_est()) and not eclipsing util_est's LSB
> > value?
>
> As this would be fixing two issues at once, it's probably preferable.
>
> [...]
>
> >  kernel/sched/fair.c |  5 +++--
> >  kernel/sched/pelt.h | 11 ++++++-----
> >  2 files changed, 9 insertions(+), 7 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 1d75af1ecfb4..dd30e362c3cc 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -3902,7 +3902,7 @@ static inline unsigned long _task_util_est(struct task_struct *p)
> >  {
> >       struct util_est ue = READ_ONCE(p->se.avg.util_est);
> >
> > -     return (max(ue.ewma, ue.enqueued) | UTIL_AVG_UNCHANGED);
> > +     return max(ue.ewma, (ue.enqueued & ~UTIL_AVG_UNCHANGED));
> >  }
> >
> >  static inline unsigned long task_util_est(struct task_struct *p)
> > @@ -4002,7 +4002,7 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
> >        * Reset EWMA on utilization increases, the moving average is used only
> >        * to smooth utilization decreases.
> >        */
>
> Needs to be updated to add:
>
>         last_enqueued_diff = ue.enqueued & ~UTIL_AVG_UNCHANGED;

The flag had been cleared before, otherwise would return earlier, so
there is no need to clear this flag again.

>
> > -     ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED);
> > +     ue.enqueued = task_util(p);
> >       if (sched_feat(UTIL_EST_FASTUP)) {
> >               if (ue.ewma < ue.enqueued) {
> >                       ue.ewma = ue.enqueued;
> > @@ -4051,6 +4051,7 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
> >       ue.ewma  += last_ewma_diff;
> >       ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
> >  done:
> > +     ue.enqueued |= UTIL_AVG_UNCHANGED;
> >       WRITE_ONCE(p->se.avg.util_est, ue);
> >
> >       trace_sched_util_est_se_tp(&p->se);
> > diff --git a/kernel/sched/pelt.h b/kernel/sched/pelt.h
> > index 1462846d244e..476faf61f14a 100644

Re: [PATCH v2] sched/pelt: Keep UTIL_AVG_UNCHANGED flag in sync when calculating last_enqueued_diff

[Vincent Donnefort]

> > >
> > >  static inline unsigned long task_util_est(struct task_struct *p)
> > > @@ -4002,7 +4002,7 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
> > >        * Reset EWMA on utilization increases, the moving average is used only
> > >        * to smooth utilization decreases.
> > >        */
> >
> > Needs to be updated to add:
> >
> >         last_enqueued_diff = ue.enqueued & ~UTIL_AVG_UNCHANGED;
> 
> The flag had been cleared before, otherwise would return earlier, so
> there is no need to clear this flag again.

Indeed, my bad. All good then.

-- 
Vincent