[PATCH v2] sched/uclamp: Fix overzealous type replacement

[PATCH v2] sched/uclamp: Fix overzealous type replacement

[Valentin Schneider]

Some uclamp helpers had their return type changed from 'unsigned int' to
'enum uclamp_id' by commit

  0413d7f33e60 ("sched/uclamp: Always use 'enum uclamp_id' for clamp_id values")

but it happens that some do return a value in the [0, SCHED_CAPACITY_SCALE]
range, which should really be unsigned int. The affected helpers are
uclamp_none(), uclamp_rq_max_value() and uclamp_eff_value(). Fix those up.

Note that this doesn't lead to any obj diff using a relatively recent
aarch64 compiler (8.3-2019.03). The current code of e.g. uclamp_eff_value()
properly returns an 11 bit value (bits_per(1024)) and doesn't seem to do
anything funny. I'm still marking this as fixing the above commit to be on
the safe side.

Fixes: 0413d7f33e60 ("sched/uclamp: Always use 'enum uclamp_id' for clamp_id values")
Reviewed-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
---
v2 changes:
o Also fix uclamp_none() (Vincent)
o Collect reviewed-by
o Slightly reword changelog
---
 kernel/sched/core.c  | 6 +++---
 kernel/sched/sched.h | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 513a4794ff36..3ceff1c93ef1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -810,7 +810,7 @@ static inline unsigned int uclamp_bucket_base_value(unsigned int clamp_value)
 	return UCLAMP_BUCKET_DELTA * uclamp_bucket_id(clamp_value);
 }
 
-static inline enum uclamp_id uclamp_none(enum uclamp_id clamp_id)
+static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
 {
 	if (clamp_id == UCLAMP_MIN)
 		return 0;
@@ -853,7 +853,7 @@ static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
 }
 
 static inline
-enum uclamp_id uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
+unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
 				   unsigned int clamp_value)
 {
 	struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket;
@@ -918,7 +918,7 @@ uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
 	return uc_req;
 }
 
-enum uclamp_id uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
+unsigned int uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
 {
 	struct uclamp_se uc_eff;
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 05c282775f21..280a3c735935 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2300,7 +2300,7 @@ static inline void cpufreq_update_util(struct rq *rq, unsigned int flags) {}
 #endif /* CONFIG_CPU_FREQ */
 
 #ifdef CONFIG_UCLAMP_TASK
-enum uclamp_id uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id);
+unsigned int uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id);
 
 static __always_inline
 unsigned int uclamp_util_with(struct rq *rq, unsigned int util,
-- 
2.22.0

Re: [PATCH v2] sched/uclamp: Fix overzealous type replacement

[Vincent Guittot]

On Fri, 15 Nov 2019 at 11:39, Valentin Schneider
<valentin.schneider@arm.com> wrote:
>
> Some uclamp helpers had their return type changed from 'unsigned int' to
> 'enum uclamp_id' by commit
>
>   0413d7f33e60 ("sched/uclamp: Always use 'enum uclamp_id' for clamp_id values")
>
> but it happens that some do return a value in the [0, SCHED_CAPACITY_SCALE]
> range, which should really be unsigned int. The affected helpers are
> uclamp_none(), uclamp_rq_max_value() and uclamp_eff_value(). Fix those up.
>
> Note that this doesn't lead to any obj diff using a relatively recent
> aarch64 compiler (8.3-2019.03). The current code of e.g. uclamp_eff_value()
> properly returns an 11 bit value (bits_per(1024)) and doesn't seem to do
> anything funny. I'm still marking this as fixing the above commit to be on
> the safe side.
>
> Fixes: 0413d7f33e60 ("sched/uclamp: Always use 'enum uclamp_id' for clamp_id values")
> Reviewed-by: Qais Yousef <qais.yousef@arm.com>
> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
> ---
> v2 changes:
> o Also fix uclamp_none() (Vincent)
> o Collect reviewed-by
> o Slightly reword changelog
> ---
>  kernel/sched/core.c  | 6 +++---
>  kernel/sched/sched.h | 2 +-
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 513a4794ff36..3ceff1c93ef1 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -810,7 +810,7 @@ static inline unsigned int uclamp_bucket_base_value(unsigned int clamp_value)
>         return UCLAMP_BUCKET_DELTA * uclamp_bucket_id(clamp_value);
>  }
>
> -static inline enum uclamp_id uclamp_none(enum uclamp_id clamp_id)
> +static inline unsigned int uclamp_none(enum uclamp_id clamp_id)

Out of curiosity why uclamp decided to use unsigned int to manipulate
utilization instead of unsigned long which is the type of util_avg ?

>  {
>         if (clamp_id == UCLAMP_MIN)
>                 return 0;
> @@ -853,7 +853,7 @@ static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
>  }
>
>  static inline
> -enum uclamp_id uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
> +unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
>                                    unsigned int clamp_value)
>  {
>         struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket;
> @@ -918,7 +918,7 @@ uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
>         return uc_req;
>  }
>
> -enum uclamp_id uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
> +unsigned int uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
>  {
>         struct uclamp_se uc_eff;
>
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 05c282775f21..280a3c735935 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2300,7 +2300,7 @@ static inline void cpufreq_update_util(struct rq *rq, unsigned int flags) {}
>  #endif /* CONFIG_CPU_FREQ */
>
>  #ifdef CONFIG_UCLAMP_TASK
> -enum uclamp_id uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id);
> +unsigned int uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id);
>
>  static __always_inline
>  unsigned int uclamp_util_with(struct rq *rq, unsigned int util,
> --
> 2.22.0
>

Re: [PATCH v2] sched/uclamp: Fix overzealous type replacement

[Valentin Schneider]

On 15/11/2019 14:07, Vincent Guittot wrote:
>> -static inline enum uclamp_id uclamp_none(enum uclamp_id clamp_id)
>> +static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
> 
> Out of curiosity why uclamp decided to use unsigned int to manipulate
> utilization instead of unsigned long which is the type of util_avg ?
> 

I didn't stare at the discussion much, but I think it stems from the
design choices behind struct uclamp_se: everything is crammed in an unsigned
int bitfield. Let me see if I can find some relevant mails.

Re: [PATCH v2] sched/uclamp: Fix overzealous type replacement

[Valentin Schneider]

On 15/11/2019 14:29, Valentin Schneider wrote:
> On 15/11/2019 14:07, Vincent Guittot wrote:
>>> -static inline enum uclamp_id uclamp_none(enum uclamp_id clamp_id)
>>> +static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
>>
>> Out of curiosity why uclamp decided to use unsigned int to manipulate
>> utilization instead of unsigned long which is the type of util_avg ?
>>
> 
> I didn't stare at the discussion much, but I think it stems from the
> design choices behind struct uclamp_se: everything is crammed in an unsigned
> int bitfield. Let me see if I can find some relevant mails.
> 

So I think a relevant mail is:

https://lore.kernel.org/lkml/20180912174236.GB24106@hirez.programming.kicks-ass.net/

Other than that, the uclamp_se.value field was 'int' in v1 and has been
'unsigned int' for all following versions. uclamp_bucket.value is a bitfield
of an 'unsigned long' just because we want more headroom for the tasks count,
AFAICT.

Re: [PATCH v2] sched/uclamp: Fix overzealous type replacement

[Vincent Guittot]

On Fri, 15 Nov 2019 at 18:10, Valentin Schneider
<valentin.schneider@arm.com> wrote:
>
> On 15/11/2019 14:29, Valentin Schneider wrote:
> > On 15/11/2019 14:07, Vincent Guittot wrote:
> >>> -static inline enum uclamp_id uclamp_none(enum uclamp_id clamp_id)
> >>> +static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
> >>
> >> Out of curiosity why uclamp decided to use unsigned int to manipulate
> >> utilization instead of unsigned long which is the type of util_avg ?
> >>
> >
> > I didn't stare at the discussion much, but I think it stems from the
> > design choices behind struct uclamp_se: everything is crammed in an unsigned
> > int bitfield. Let me see if I can find some relevant mails.
> >
>
> So I think a relevant mail is:
>
> https://lore.kernel.org/lkml/20180912174236.GB24106@hirez.programming.kicks-ass.net/
>
> Other than that, the uclamp_se.value field was 'int' in v1 and has been
> 'unsigned int' for all following versions. uclamp_bucket.value is a bitfield
> of an 'unsigned long' just because we want more headroom for the tasks count,
> AFAICT.

Thanks for the pointer and deep diving in the email threads

Re: [PATCH v2] sched/uclamp: Fix overzealous type replacement

[Vincent Guittot]

On Fri, 15 Nov 2019 at 11:39, Valentin Schneider
<valentin.schneider@arm.com> wrote:
>
> Some uclamp helpers had their return type changed from 'unsigned int' to
> 'enum uclamp_id' by commit
>
>   0413d7f33e60 ("sched/uclamp: Always use 'enum uclamp_id' for clamp_id values")
>
> but it happens that some do return a value in the [0, SCHED_CAPACITY_SCALE]
> range, which should really be unsigned int. The affected helpers are
> uclamp_none(), uclamp_rq_max_value() and uclamp_eff_value(). Fix those up.
>
> Note that this doesn't lead to any obj diff using a relatively recent
> aarch64 compiler (8.3-2019.03). The current code of e.g. uclamp_eff_value()
> properly returns an 11 bit value (bits_per(1024)) and doesn't seem to do
> anything funny. I'm still marking this as fixing the above commit to be on
> the safe side.
>
> Fixes: 0413d7f33e60 ("sched/uclamp: Always use 'enum uclamp_id' for clamp_id values")
> Reviewed-by: Qais Yousef <qais.yousef@arm.com>
> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>

Acked-by: Vincent Guittot <vincent.guittot@linaro.org>

> ---
> v2 changes:
> o Also fix uclamp_none() (Vincent)
> o Collect reviewed-by
> o Slightly reword changelog
> ---
>  kernel/sched/core.c  | 6 +++---
>  kernel/sched/sched.h | 2 +-
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 513a4794ff36..3ceff1c93ef1 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -810,7 +810,7 @@ static inline unsigned int uclamp_bucket_base_value(unsigned int clamp_value)
>         return UCLAMP_BUCKET_DELTA * uclamp_bucket_id(clamp_value);
>  }
>
> -static inline enum uclamp_id uclamp_none(enum uclamp_id clamp_id)
> +static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
>  {
>         if (clamp_id == UCLAMP_MIN)
>                 return 0;
> @@ -853,7 +853,7 @@ static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
>  }
>
>  static inline
> -enum uclamp_id uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
> +unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
>                                    unsigned int clamp_value)
>  {
>         struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket;
> @@ -918,7 +918,7 @@ uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
>         return uc_req;
>  }
>
> -enum uclamp_id uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
> +unsigned int uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
>  {
>         struct uclamp_se uc_eff;
>
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 05c282775f21..280a3c735935 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2300,7 +2300,7 @@ static inline void cpufreq_update_util(struct rq *rq, unsigned int flags) {}
>  #endif /* CONFIG_CPU_FREQ */
>
>  #ifdef CONFIG_UCLAMP_TASK
> -enum uclamp_id uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id);
> +unsigned int uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id);
>
>  static __always_inline
>  unsigned int uclamp_util_with(struct rq *rq, unsigned int util,
> --
> 2.22.0
>

Re: [PATCH v2] sched/uclamp: Fix overzealous type replacement

[Peter Zijlstra]

On Fri, Nov 15, 2019 at 06:34:19PM +0100, Vincent Guittot wrote:
> On Fri, 15 Nov 2019 at 18:10, Valentin Schneider
> <valentin.schneider@arm.com> wrote:
> >
> > On 15/11/2019 14:29, Valentin Schneider wrote:
> > > On 15/11/2019 14:07, Vincent Guittot wrote:
> > >>> -static inline enum uclamp_id uclamp_none(enum uclamp_id clamp_id)
> > >>> +static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
> > >>
> > >> Out of curiosity why uclamp decided to use unsigned int to manipulate
> > >> utilization instead of unsigned long which is the type of util_avg ?
> > >>
> > >
> > > I didn't stare at the discussion much, but I think it stems from the
> > > design choices behind struct uclamp_se: everything is crammed in an unsigned
> > > int bitfield. Let me see if I can find some relevant mails.
> > >
> >
> > So I think a relevant mail is:
> >
> > https://lore.kernel.org/lkml/20180912174236.GB24106@hirez.programming.kicks-ass.net/
> >
> > Other than that, the uclamp_se.value field was 'int' in v1 and has been
> > 'unsigned int' for all following versions. uclamp_bucket.value is a bitfield
> > of an 'unsigned long' just because we want more headroom for the tasks count,
> > AFAICT.
> 
> Thanks for the pointer and deep diving in the email threads

It was all in an effort to minimize the number of cachelines touched to
maintain this data.

[tip: sched/core] sched/uclamp: Fix overzealous type replacement

[tip-bot2 for Valentin Schneider]

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

Commit-ID:     7763baace1b738d65efa46d68326c9406311c6bf
Gitweb:        https://git.kernel.org/tip/7763baace1b738d65efa46d68326c9406311c6bf
Author:        Valentin Schneider <valentin.schneider@arm.com>
AuthorDate:    Fri, 15 Nov 2019 10:39:08 
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sun, 17 Nov 2019 10:46:05 +01:00

sched/uclamp: Fix overzealous type replacement

Some uclamp helpers had their return type changed from 'unsigned int' to
'enum uclamp_id' by commit

  0413d7f33e60 ("sched/uclamp: Always use 'enum uclamp_id' for clamp_id values")

but it happens that some do return a value in the [0, SCHED_CAPACITY_SCALE]
range, which should really be unsigned int. The affected helpers are
uclamp_none(), uclamp_rq_max_value() and uclamp_eff_value(). Fix those up.

Note that this doesn't lead to any obj diff using a relatively recent
aarch64 compiler (8.3-2019.03). The current code of e.g. uclamp_eff_value()
properly returns an 11 bit value (bits_per(1024)) and doesn't seem to do
anything funny. I'm still marking this as fixing the above commit to be on
the safe side.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Qais Yousef <qais.yousef@arm.com>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar.Eggemann@arm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: patrick.bellasi@matbug.net
Cc: qperret@google.com
Cc: surenb@google.com
Cc: tj@kernel.org
Fixes: 0413d7f33e60 ("sched/uclamp: Always use 'enum uclamp_id' for clamp_id values")
Link: https://lkml.kernel.org/r/20191115103908.27610-1-valentin.schneider@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/core.c  | 6 +++---
 kernel/sched/sched.h | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 513a479..3ceff1c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -810,7 +810,7 @@ static inline unsigned int uclamp_bucket_base_value(unsigned int clamp_value)
 	return UCLAMP_BUCKET_DELTA * uclamp_bucket_id(clamp_value);
 }
 
-static inline enum uclamp_id uclamp_none(enum uclamp_id clamp_id)
+static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
 {
 	if (clamp_id == UCLAMP_MIN)
 		return 0;
@@ -853,7 +853,7 @@ static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
 }
 
 static inline
-enum uclamp_id uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
+unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
 				   unsigned int clamp_value)
 {
 	struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket;
@@ -918,7 +918,7 @@ uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
 	return uc_req;
 }
 
-enum uclamp_id uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
+unsigned int uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
 {
 	struct uclamp_se uc_eff;
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 05c2827..280a3c7 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2300,7 +2300,7 @@ static inline void cpufreq_update_util(struct rq *rq, unsigned int flags) {}
 #endif /* CONFIG_CPU_FREQ */
 
 #ifdef CONFIG_UCLAMP_TASK
-enum uclamp_id uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id);
+unsigned int uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id);
 
 static __always_inline
 unsigned int uclamp_util_with(struct rq *rq, unsigned int util,