[V2,1/2] sched/core: Rename and move schedutil_cpu_util() to core.c

Commit Message

Viresh Kumar Oct. 23, 2020, 10:20 a.m. UTC

There is nothing schedutil specific in schedutil_cpu_util(), move it to
core.c and rename it to sched_cpu_util(), so it can be used from other
parts of the kernel as well.

The cpufreq_cooling stuff will make use of this in a later commit.

Signed-off-by: Viresh Kumar <[e-mail]>
---
 include/linux/sched.h            |  19 +++++
 kernel/sched/core.c              | 113 ++++++++++++++++++++++++++++++
 kernel/sched/cpufreq_schedutil.c | 116 +------------------------------
 kernel/sched/fair.c              |   6 +-
 kernel/sched/sched.h             |  29 +-------
 5 files changed, 140 insertions(+), 143 deletions(-)

Comments

Peter Zijlstra Oct. 23, 2020, 10:34 a.m. UTC | #1

On Fri, Oct 23, 2020 at 03:50:20PM +0530, Viresh Kumar wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index d2003a7d5ab5..369ff54d11d4 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5117,6 +5117,119 @@ struct task_struct *idle_task(int cpu)
>  	return cpu_rq(cpu)->idle;
>  }
>  
> +/*
> + * This function computes an effective utilization for the given CPU, to be
> + * used for frequency selection given the linear relation: f = u * f_max.
> + *
> + * The scheduler tracks the following metrics:
> + *
> + *   cpu_util_{cfs,rt,dl,irq}()
> + *   cpu_bw_dl()
> + *
> + * Where the cfs,rt and dl util numbers are tracked with the same metric and
> + * synchronized windows and are thus directly comparable.
> + *
> + * The cfs,rt,dl utilization are the running times measured with rq->clock_task
> + * which excludes things like IRQ and steal-time. These latter are then accrued
> + * in the irq utilization.
> + *
> + * The DL bandwidth number otoh is not a measured metric but a value computed
> + * based on the task model parameters and gives the minimal utilization
> + * required to meet deadlines.
> + */
> +unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
> +				 unsigned long max, enum cpu_util_type type,
> +				 struct task_struct *p)
> +{
	...
> +}
> +
> +unsigned long sched_cpu_util(int cpu, enum cpu_util_type type,
> +			     unsigned long max)
> +{
> +	return effective_cpu_util(cpu, cpu_util_cfs(cpu_rq(cpu)), max, type,
> +				  NULL);
> +}

Shouldn't all that be: #ifdef CONFIG_SMP ?

Vincent Guittot Oct. 23, 2020, 10:43 a.m. UTC | #2

On Fri, 23 Oct 2020 at 12:20, Viresh Kumar <[e-mail]> wrote:
>
> There is nothing schedutil specific in schedutil_cpu_util(), move it to
> core.c and rename it to sched_cpu_util(), so it can be used from other

I wonder if pelt.c would be a better place for this than core.c ?

> parts of the kernel as well.
>
> The cpufreq_cooling stuff will make use of this in a later commit.
>
> Signed-off-by: Viresh Kumar <[e-mail]>
> ---
>  include/linux/sched.h            |  19 +++++
>  kernel/sched/core.c              | 113 ++++++++++++++++++++++++++++++
>  kernel/sched/cpufreq_schedutil.c | 116 +------------------------------
>  kernel/sched/fair.c              |   6 +-
>  kernel/sched/sched.h             |  29 +-------
>  5 files changed, 140 insertions(+), 143 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 393db0690101..3c27c10141cb 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1930,6 +1930,25 @@ extern long sched_getaffinity(pid_t pid, struct cpumask *mask);
>  #define TASK_SIZE_OF(tsk)      TASK_SIZE
>  #endif
>
> +/**
> + * enum cpu_util_type - CPU utilization type
> + * @FREQUENCY_UTIL:    Utilization used to select frequency
> + * @ENERGY_UTIL:       Utilization used during energy calculation
> + *
> + * The utilization signals of all scheduling classes (CFS/RT/DL) and IRQ time
> + * need to be aggregated differently depending on the usage made of them. This
> + * enum is used within sched_cpu_util() to differentiate the types of
> + * utilization expected by the callers, and adjust the aggregation accordingly.
> + */
> +enum cpu_util_type {
> +       FREQUENCY_UTIL,
> +       ENERGY_UTIL,
> +};
> +
> +/* Returns effective CPU utilization, as seen by the scheduler */
> +unsigned long sched_cpu_util(int cpu, enum cpu_util_type type,
> +                            unsigned long max);
> +
>  #ifdef CONFIG_RSEQ
>
>  /*
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index d2003a7d5ab5..369ff54d11d4 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5117,6 +5117,119 @@ struct task_struct *idle_task(int cpu)
>         return cpu_rq(cpu)->idle;
>  }
>
> +/*
> + * This function computes an effective utilization for the given CPU, to be
> + * used for frequency selection given the linear relation: f = u * f_max.
> + *
> + * The scheduler tracks the following metrics:
> + *
> + *   cpu_util_{cfs,rt,dl,irq}()
> + *   cpu_bw_dl()
> + *
> + * Where the cfs,rt and dl util numbers are tracked with the same metric and
> + * synchronized windows and are thus directly comparable.
> + *
> + * The cfs,rt,dl utilization are the running times measured with rq->clock_task
> + * which excludes things like IRQ and steal-time. These latter are then accrued
> + * in the irq utilization.
> + *
> + * The DL bandwidth number otoh is not a measured metric but a value computed
> + * based on the task model parameters and gives the minimal utilization
> + * required to meet deadlines.
> + */
> +unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
> +                                unsigned long max, enum cpu_util_type type,
> +                                struct task_struct *p)
> +{
> +       unsigned long dl_util, util, irq;
> +       struct rq *rq = cpu_rq(cpu);
> +
> +       if (!uclamp_is_used() &&
> +           type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt)) {
> +               return max;
> +       }
> +
> +       /*
> +        * Early check to see if IRQ/steal time saturates the CPU, can be
> +        * because of inaccuracies in how we track these -- see
> +        * update_irq_load_avg().
> +        */
> +       irq = cpu_util_irq(rq);
> +       if (unlikely(irq >= max))
> +               return max;
> +
> +       /*
> +        * Because the time spend on RT/DL tasks is visible as 'lost' time to
> +        * CFS tasks and we use the same metric to track the effective
> +        * utilization (PELT windows are synchronized) we can directly add them
> +        * to obtain the CPU's actual utilization.
> +        *
> +        * CFS and RT utilization can be boosted or capped, depending on
> +        * utilization clamp constraints requested by currently RUNNABLE
> +        * tasks.
> +        * When there are no CFS RUNNABLE tasks, clamps are released and
> +        * frequency will be gracefully reduced with the utilization decay.
> +        */
> +       util = util_cfs + cpu_util_rt(rq);
> +       if (type == FREQUENCY_UTIL)
> +               util = uclamp_rq_util_with(rq, util, p);
> +
> +       dl_util = cpu_util_dl(rq);
> +
> +       /*
> +        * For frequency selection we do not make cpu_util_dl() a permanent part
> +        * of this sum because we want to use cpu_bw_dl() later on, but we need
> +        * to check if the CFS+RT+DL sum is saturated (ie. no idle time) such
> +        * that we select f_max when there is no idle time.
> +        *
> +        * NOTE: numerical errors or stop class might cause us to not quite hit
> +        * saturation when we should -- something for later.
> +        */
> +       if (util + dl_util >= max)
> +               return max;
> +
> +       /*
> +        * OTOH, for energy computation we need the estimated running time, so
> +        * include util_dl and ignore dl_bw.
> +        */
> +       if (type == ENERGY_UTIL)
> +               util += dl_util;
> +
> +       /*
> +        * There is still idle time; further improve the number by using the
> +        * irq metric. Because IRQ/steal time is hidden from the task clock we
> +        * need to scale the task numbers:
> +        *
> +        *              max - irq
> +        *   U' = irq + --------- * U
> +        *                 max
> +        */
> +       util = scale_irq_capacity(util, irq, max);
> +       util += irq;
> +
> +       /*
> +        * Bandwidth required by DEADLINE must always be granted while, for
> +        * FAIR and RT, we use blocked utilization of IDLE CPUs as a mechanism
> +        * to gracefully reduce the frequency when no tasks show up for longer
> +        * periods of time.
> +        *
> +        * Ideally we would like to set bw_dl as min/guaranteed freq and util +
> +        * bw_dl as requested freq. However, cpufreq is not yet ready for such
> +        * an interface. So, we only do the latter for now.
> +        */
> +       if (type == FREQUENCY_UTIL)
> +               util += cpu_bw_dl(rq);
> +
> +       return min(max, util);
> +}
> +
> +unsigned long sched_cpu_util(int cpu, enum cpu_util_type type,
> +                            unsigned long max)
> +{
> +       return effective_cpu_util(cpu, cpu_util_cfs(cpu_rq(cpu)), max, type,
> +                                 NULL);
> +}
> +
>  /**
>   * find_process_by_pid - find a process with a matching PID value.
>   * @pid: the pid in question.
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 5ae7b4e6e8d6..0c5c61a095f6 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -169,122 +169,12 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy,
>         return cpufreq_driver_resolve_freq(policy, freq);
>  }
>
> -/*
> - * This function computes an effective utilization for the given CPU, to be
> - * used for frequency selection given the linear relation: f = u * f_max.
> - *
> - * The scheduler tracks the following metrics:
> - *
> - *   cpu_util_{cfs,rt,dl,irq}()
> - *   cpu_bw_dl()
> - *
> - * Where the cfs,rt and dl util numbers are tracked with the same metric and
> - * synchronized windows and are thus directly comparable.
> - *
> - * The cfs,rt,dl utilization are the running times measured with rq->clock_task
> - * which excludes things like IRQ and steal-time. These latter are then accrued
> - * in the irq utilization.
> - *
> - * The DL bandwidth number otoh is not a measured metric but a value computed
> - * based on the task model parameters and gives the minimal utilization
> - * required to meet deadlines.
> - */
> -unsigned long schedutil_cpu_util(int cpu, unsigned long util_cfs,
> -                                unsigned long max, enum schedutil_type type,
> -                                struct task_struct *p)
> -{
> -       unsigned long dl_util, util, irq;
> -       struct rq *rq = cpu_rq(cpu);
> -
> -       if (!uclamp_is_used() &&
> -           type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt)) {
> -               return max;
> -       }
> -
> -       /*
> -        * Early check to see if IRQ/steal time saturates the CPU, can be
> -        * because of inaccuracies in how we track these -- see
> -        * update_irq_load_avg().
> -        */
> -       irq = cpu_util_irq(rq);
> -       if (unlikely(irq >= max))
> -               return max;
> -
> -       /*
> -        * Because the time spend on RT/DL tasks is visible as 'lost' time to
> -        * CFS tasks and we use the same metric to track the effective
> -        * utilization (PELT windows are synchronized) we can directly add them
> -        * to obtain the CPU's actual utilization.
> -        *
> -        * CFS and RT utilization can be boosted or capped, depending on
> -        * utilization clamp constraints requested by currently RUNNABLE
> -        * tasks.
> -        * When there are no CFS RUNNABLE tasks, clamps are released and
> -        * frequency will be gracefully reduced with the utilization decay.
> -        */
> -       util = util_cfs + cpu_util_rt(rq);
> -       if (type == FREQUENCY_UTIL)
> -               util = uclamp_rq_util_with(rq, util, p);
> -
> -       dl_util = cpu_util_dl(rq);
> -
> -       /*
> -        * For frequency selection we do not make cpu_util_dl() a permanent part
> -        * of this sum because we want to use cpu_bw_dl() later on, but we need
> -        * to check if the CFS+RT+DL sum is saturated (ie. no idle time) such
> -        * that we select f_max when there is no idle time.
> -        *
> -        * NOTE: numerical errors or stop class might cause us to not quite hit
> -        * saturation when we should -- something for later.
> -        */
> -       if (util + dl_util >= max)
> -               return max;
> -
> -       /*
> -        * OTOH, for energy computation we need the estimated running time, so
> -        * include util_dl and ignore dl_bw.
> -        */
> -       if (type == ENERGY_UTIL)
> -               util += dl_util;
> -
> -       /*
> -        * There is still idle time; further improve the number by using the
> -        * irq metric. Because IRQ/steal time is hidden from the task clock we
> -        * need to scale the task numbers:
> -        *
> -        *              max - irq
> -        *   U' = irq + --------- * U
> -        *                 max
> -        */
> -       util = scale_irq_capacity(util, irq, max);
> -       util += irq;
> -
> -       /*
> -        * Bandwidth required by DEADLINE must always be granted while, for
> -        * FAIR and RT, we use blocked utilization of IDLE CPUs as a mechanism
> -        * to gracefully reduce the frequency when no tasks show up for longer
> -        * periods of time.
> -        *
> -        * Ideally we would like to set bw_dl as min/guaranteed freq and util +
> -        * bw_dl as requested freq. However, cpufreq is not yet ready for such
> -        * an interface. So, we only do the latter for now.
> -        */
> -       if (type == FREQUENCY_UTIL)
> -               util += cpu_bw_dl(rq);
> -
> -       return min(max, util);
> -}
> -
>  static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
>  {
> -       struct rq *rq = cpu_rq(sg_cpu->cpu);
> -       unsigned long util = cpu_util_cfs(rq);
> -       unsigned long max = arch_scale_cpu_capacity(sg_cpu->cpu);
> -
> -       sg_cpu->max = max;
> -       sg_cpu->bw_dl = cpu_bw_dl(rq);
> +       sg_cpu->max = arch_scale_cpu_capacity(sg_cpu->cpu);
> +       sg_cpu->bw_dl = cpu_bw_dl(cpu_rq(sg_cpu->cpu));
>
> -       return schedutil_cpu_util(sg_cpu->cpu, util, max, FREQUENCY_UTIL, NULL);
> +       return sched_cpu_util(sg_cpu->cpu, FREQUENCY_UTIL, sg_cpu->max);
>  }
>
>  /**
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index aa4c6227cd6d..52e2d866e875 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6499,7 +6499,7 @@ compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
>                  * is already enough to scale the EM reported power
>                  * consumption at the (eventually clamped) cpu_capacity.
>                  */
> -               sum_util += schedutil_cpu_util(cpu, util_cfs, cpu_cap,
> +               sum_util += effective_cpu_util(cpu, util_cfs, cpu_cap,
>                                                ENERGY_UTIL, NULL);
>
>                 /*
> @@ -6509,7 +6509,7 @@ compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
>                  * NOTE: in case RT tasks are running, by default the
>                  * FREQUENCY_UTIL's utilization can be max OPP.
>                  */
> -               cpu_util = schedutil_cpu_util(cpu, util_cfs, cpu_cap,
> +               cpu_util = effective_cpu_util(cpu, util_cfs, cpu_cap,
>                                               FREQUENCY_UTIL, tsk);
>                 max_util = max(max_util, cpu_util);
>         }
> @@ -6607,7 +6607,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
>                          * IOW, placing the task there would make the CPU
>                          * overutilized. Take uclamp into account to see how
>                          * much capacity we can get out of the CPU; this is
> -                        * aligned with schedutil_cpu_util().
> +                        * aligned with sched_cpu_util().
>                          */
>                         util = uclamp_rq_util_with(cpu_rq(cpu), util, p);
>                         if (!fits_capacity(util, cpu_cap))
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index df80bfcea92e..0f0439344eec 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2486,25 +2486,8 @@ static inline unsigned long capacity_orig_of(int cpu)
>  }
>  #endif
>
> -/**
> - * enum schedutil_type - CPU utilization type
> - * @FREQUENCY_UTIL:    Utilization used to select frequency
> - * @ENERGY_UTIL:       Utilization used during energy calculation
> - *
> - * The utilization signals of all scheduling classes (CFS/RT/DL) and IRQ time
> - * need to be aggregated differently depending on the usage made of them. This
> - * enum is used within schedutil_freq_util() to differentiate the types of
> - * utilization expected by the callers, and adjust the aggregation accordingly.
> - */
> -enum schedutil_type {
> -       FREQUENCY_UTIL,
> -       ENERGY_UTIL,
> -};
> -
> -#ifdef CONFIG_CPU_FREQ_GOV_SCHEDUTIL
> -
> -unsigned long schedutil_cpu_util(int cpu, unsigned long util_cfs,
> -                                unsigned long max, enum schedutil_type type,
> +unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
> +                                unsigned long max, enum cpu_util_type type,
>                                  struct task_struct *p);
>
>  static inline unsigned long cpu_bw_dl(struct rq *rq)
> @@ -2533,14 +2516,6 @@ static inline unsigned long cpu_util_rt(struct rq *rq)
>  {
>         return READ_ONCE(rq->avg_rt.util_avg);
>  }
> -#else /* CONFIG_CPU_FREQ_GOV_SCHEDUTIL */
> -static inline unsigned long schedutil_cpu_util(int cpu, unsigned long util_cfs,
> -                                unsigned long max, enum schedutil_type type,
> -                                struct task_struct *p)
> -{
> -       return 0;
> -}
> -#endif /* CONFIG_CPU_FREQ_GOV_SCHEDUTIL */
>
>  #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
>  static inline unsigned long cpu_util_irq(struct rq *rq)
> --
> 2.25.0.rc1.19.g042ed3e048af
>

Viresh Kumar Oct. 23, 2020, 10:54 a.m. UTC | #3

On 23-10-20, 12:34, Peter Zijlstra wrote:
> On Fri, Oct 23, 2020 at 03:50:20PM +0530, Viresh Kumar wrote:
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index d2003a7d5ab5..369ff54d11d4 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -5117,6 +5117,119 @@ struct task_struct *idle_task(int cpu)
> >  	return cpu_rq(cpu)->idle;
> >  }
> >  
> > +/*
> > + * This function computes an effective utilization for the given CPU, to be
> > + * used for frequency selection given the linear relation: f = u * f_max.
> > + *
> > + * The scheduler tracks the following metrics:
> > + *
> > + *   cpu_util_{cfs,rt,dl,irq}()
> > + *   cpu_bw_dl()
> > + *
> > + * Where the cfs,rt and dl util numbers are tracked with the same metric and
> > + * synchronized windows and are thus directly comparable.
> > + *
> > + * The cfs,rt,dl utilization are the running times measured with rq->clock_task
> > + * which excludes things like IRQ and steal-time. These latter are then accrued
> > + * in the irq utilization.
> > + *
> > + * The DL bandwidth number otoh is not a measured metric but a value computed
> > + * based on the task model parameters and gives the minimal utilization
> > + * required to meet deadlines.
> > + */
> > +unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
> > +				 unsigned long max, enum cpu_util_type type,
> > +				 struct task_struct *p)
> > +{
> 	...
> > +}
> > +
> > +unsigned long sched_cpu_util(int cpu, enum cpu_util_type type,
> > +			     unsigned long max)
> > +{
> > +	return effective_cpu_util(cpu, cpu_util_cfs(cpu_rq(cpu)), max, type,
> > +				  NULL);
> > +}
> 
> Shouldn't all that be: #ifdef CONFIG_SMP ?

I didn't realize that these matrices are only available in case of SMP
and that's why schedutil isn't available for !SMP. I wonder what we
should be doing in cpufreq_cooling now ? Make it depend on SMP ? Or
calculate load the traditional way (the stuff I just removed) for !SMP
case ?

:)

Viresh Kumar Oct. 23, 2020, 10:55 a.m. UTC | #4

On 23-10-20, 12:43, Vincent Guittot wrote:
> On Fri, 23 Oct 2020 at 12:20, Viresh Kumar <[e-mail]> wrote:
> >
> > There is nothing schedutil specific in schedutil_cpu_util(), move it to
> > core.c and rename it to sched_cpu_util(), so it can be used from other
> 
> I wonder if pelt.c would be a better place for this than core.c ?

Wherever you guys ask me to move it :)

Lukasz Luba Oct. 23, 2020, 11:08 a.m. UTC | #5

On 10/23/20 11:54 AM, Viresh Kumar wrote:
> On 23-10-20, 12:34, Peter Zijlstra wrote:
>> On Fri, Oct 23, 2020 at 03:50:20PM +0530, Viresh Kumar wrote:
>>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>>> index d2003a7d5ab5..369ff54d11d4 100644
>>> --- a/kernel/sched/core.c
>>> +++ b/kernel/sched/core.c
>>> @@ -5117,6 +5117,119 @@ struct task_struct *idle_task(int cpu)
>>>   	return cpu_rq(cpu)->idle;
>>>   }
>>>   
>>> +/*
>>> + * This function computes an effective utilization for the given CPU, to be
>>> + * used for frequency selection given the linear relation: f = u * f_max.
>>> + *
>>> + * The scheduler tracks the following metrics:
>>> + *
>>> + *   cpu_util_{cfs,rt,dl,irq}()
>>> + *   cpu_bw_dl()
>>> + *
>>> + * Where the cfs,rt and dl util numbers are tracked with the same metric and
>>> + * synchronized windows and are thus directly comparable.
>>> + *
>>> + * The cfs,rt,dl utilization are the running times measured with rq->clock_task
>>> + * which excludes things like IRQ and steal-time. These latter are then accrued
>>> + * in the irq utilization.
>>> + *
>>> + * The DL bandwidth number otoh is not a measured metric but a value computed
>>> + * based on the task model parameters and gives the minimal utilization
>>> + * required to meet deadlines.
>>> + */
>>> +unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
>>> +				 unsigned long max, enum cpu_util_type type,
>>> +				 struct task_struct *p)
>>> +{
>> 	...
>>> +}
>>> +
>>> +unsigned long sched_cpu_util(int cpu, enum cpu_util_type type,
>>> +			     unsigned long max)
>>> +{
>>> +	return effective_cpu_util(cpu, cpu_util_cfs(cpu_rq(cpu)), max, type,
>>> +				  NULL);
>>> +}
>>
>> Shouldn't all that be: #ifdef CONFIG_SMP ?
> 
> I didn't realize that these matrices are only available in case of SMP
> and that's why schedutil isn't available for !SMP. I wonder what we
> should be doing in cpufreq_cooling now ? Make it depend on SMP ? Or
> calculate load the traditional way (the stuff I just removed) for !SMP
> case ?

IMO the !SMP can leave with the old design, so keeping two
implementations under #ifdef CONFIG_SMP is fair I would say in this
case.

There are popular platforms !SMP (BeagleBone, RPi1, RPiZero) but I
haven't heard anyone was using IPA on them.

Regards,
Lukasz

> 
> :)
>

Vincent Guittot Oct. 23, 2020, 12:34 p.m. UTC | #6

On Fri, 23 Oct 2020 at 12:54, Viresh Kumar <[e-mail]> wrote:
>
> On 23-10-20, 12:34, Peter Zijlstra wrote:
> > On Fri, Oct 23, 2020 at 03:50:20PM +0530, Viresh Kumar wrote:
> > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > > index d2003a7d5ab5..369ff54d11d4 100644
> > > --- a/kernel/sched/core.c
> > > +++ b/kernel/sched/core.c
> > > @@ -5117,6 +5117,119 @@ struct task_struct *idle_task(int cpu)
> > >     return cpu_rq(cpu)->idle;
> > >  }
> > >
> > > +/*
> > > + * This function computes an effective utilization for the given CPU, to be
> > > + * used for frequency selection given the linear relation: f = u * f_max.
> > > + *
> > > + * The scheduler tracks the following metrics:
> > > + *
> > > + *   cpu_util_{cfs,rt,dl,irq}()
> > > + *   cpu_bw_dl()
> > > + *
> > > + * Where the cfs,rt and dl util numbers are tracked with the same metric and
> > > + * synchronized windows and are thus directly comparable.
> > > + *
> > > + * The cfs,rt,dl utilization are the running times measured with rq->clock_task
> > > + * which excludes things like IRQ and steal-time. These latter are then accrued
> > > + * in the irq utilization.
> > > + *
> > > + * The DL bandwidth number otoh is not a measured metric but a value computed
> > > + * based on the task model parameters and gives the minimal utilization
> > > + * required to meet deadlines.
> > > + */
> > > +unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
> > > +                            unsigned long max, enum cpu_util_type type,
> > > +                            struct task_struct *p)
> > > +{
> >       ...
> > > +}
> > > +
> > > +unsigned long sched_cpu_util(int cpu, enum cpu_util_type type,
> > > +                        unsigned long max)
> > > +{
> > > +   return effective_cpu_util(cpu, cpu_util_cfs(cpu_rq(cpu)), max, type,
> > > +                             NULL);
> > > +}
> >
> > Shouldn't all that be: #ifdef CONFIG_SMP ?
>
> I didn't realize that these matrices are only available in case of SMP
> and that's why schedutil isn't available for !SMP. I wonder what we

Maybe it's time to make sched_util and pelt available for !SMP too.

With util_est and uclamp, I can see some benefits for !SMP compare to ondemand

> should be doing in cpufreq_cooling now ? Make it depend on SMP ? Or
> calculate load the traditional way (the stuff I just removed) for !SMP
> case ?
>
> :)
>
> --
> viresh

Viresh Kumar Oct. 28, 2020, 5:49 a.m. UTC | #7

On 23-10-20, 14:34, Vincent Guittot wrote:
> Maybe it's time to make sched_util and pelt available for !SMP too.
> 
> With util_est and uclamp, I can see some benefits for !SMP compare to ondemand

That's a decision you guys (sched maintainers) need to make :)

Patch

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 393db0690101..3c27c10141cb 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1930,6 +1930,25 @@  extern long sched_getaffinity(pid_t pid, struct cpumask *mask);
 #define TASK_SIZE_OF(tsk)	TASK_SIZE
 #endif
 
+/**
+ * enum cpu_util_type - CPU utilization type
+ * @FREQUENCY_UTIL:	Utilization used to select frequency
+ * @ENERGY_UTIL:	Utilization used during energy calculation
+ *
+ * The utilization signals of all scheduling classes (CFS/RT/DL) and IRQ time
+ * need to be aggregated differently depending on the usage made of them. This
+ * enum is used within sched_cpu_util() to differentiate the types of
+ * utilization expected by the callers, and adjust the aggregation accordingly.
+ */
+enum cpu_util_type {
+	FREQUENCY_UTIL,
+	ENERGY_UTIL,
+};
+
+/* Returns effective CPU utilization, as seen by the scheduler */
+unsigned long sched_cpu_util(int cpu, enum cpu_util_type type,
+			     unsigned long max);
+
 #ifdef CONFIG_RSEQ
 
 /*
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d2003a7d5ab5..369ff54d11d4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5117,6 +5117,119 @@  struct task_struct *idle_task(int cpu)
 	return cpu_rq(cpu)->idle;
 }
 
+/*
+ * This function computes an effective utilization for the given CPU, to be
+ * used for frequency selection given the linear relation: f = u * f_max.
+ *
+ * The scheduler tracks the following metrics:
+ *
+ *   cpu_util_{cfs,rt,dl,irq}()
+ *   cpu_bw_dl()
+ *
+ * Where the cfs,rt and dl util numbers are tracked with the same metric and
+ * synchronized windows and are thus directly comparable.
+ *
+ * The cfs,rt,dl utilization are the running times measured with rq->clock_task
+ * which excludes things like IRQ and steal-time. These latter are then accrued
+ * in the irq utilization.
+ *
+ * The DL bandwidth number otoh is not a measured metric but a value computed
+ * based on the task model parameters and gives the minimal utilization
+ * required to meet deadlines.
+ */
+unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
+				 unsigned long max, enum cpu_util_type type,
+				 struct task_struct *p)
+{
+	unsigned long dl_util, util, irq;
+	struct rq *rq = cpu_rq(cpu);
+
+	if (!uclamp_is_used() &&
+	    type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt)) {
+		return max;
+	}
+
+	/*
+	 * Early check to see if IRQ/steal time saturates the CPU, can be
+	 * because of inaccuracies in how we track these -- see
+	 * update_irq_load_avg().
+	 */
+	irq = cpu_util_irq(rq);
+	if (unlikely(irq >= max))
+		return max;
+
+	/*
+	 * Because the time spend on RT/DL tasks is visible as 'lost' time to
+	 * CFS tasks and we use the same metric to track the effective
+	 * utilization (PELT windows are synchronized) we can directly add them
+	 * to obtain the CPU's actual utilization.
+	 *
+	 * CFS and RT utilization can be boosted or capped, depending on
+	 * utilization clamp constraints requested by currently RUNNABLE
+	 * tasks.
+	 * When there are no CFS RUNNABLE tasks, clamps are released and
+	 * frequency will be gracefully reduced with the utilization decay.
+	 */
+	util = util_cfs + cpu_util_rt(rq);
+	if (type == FREQUENCY_UTIL)
+		util = uclamp_rq_util_with(rq, util, p);
+
+	dl_util = cpu_util_dl(rq);
+
+	/*
+	 * For frequency selection we do not make cpu_util_dl() a permanent part
+	 * of this sum because we want to use cpu_bw_dl() later on, but we need
+	 * to check if the CFS+RT+DL sum is saturated (ie. no idle time) such
+	 * that we select f_max when there is no idle time.
+	 *
+	 * NOTE: numerical errors or stop class might cause us to not quite hit
+	 * saturation when we should -- something for later.
+	 */
+	if (util + dl_util >= max)
+		return max;
+
+	/*
+	 * OTOH, for energy computation we need the estimated running time, so
+	 * include util_dl and ignore dl_bw.
+	 */
+	if (type == ENERGY_UTIL)
+		util += dl_util;
+
+	/*
+	 * There is still idle time; further improve the number by using the
+	 * irq metric. Because IRQ/steal time is hidden from the task clock we
+	 * need to scale the task numbers:
+	 *
+	 *              max - irq
+	 *   U' = irq + --------- * U
+	 *                 max
+	 */
+	util = scale_irq_capacity(util, irq, max);
+	util += irq;
+
+	/*
+	 * Bandwidth required by DEADLINE must always be granted while, for
+	 * FAIR and RT, we use blocked utilization of IDLE CPUs as a mechanism
+	 * to gracefully reduce the frequency when no tasks show up for longer
+	 * periods of time.
+	 *
+	 * Ideally we would like to set bw_dl as min/guaranteed freq and util +
+	 * bw_dl as requested freq. However, cpufreq is not yet ready for such
+	 * an interface. So, we only do the latter for now.
+	 */
+	if (type == FREQUENCY_UTIL)
+		util += cpu_bw_dl(rq);
+
+	return min(max, util);
+}
+
+unsigned long sched_cpu_util(int cpu, enum cpu_util_type type,
+			     unsigned long max)
+{
+	return effective_cpu_util(cpu, cpu_util_cfs(cpu_rq(cpu)), max, type,
+				  NULL);
+}
+
 /**
  * find_process_by_pid - find a process with a matching PID value.
  * @pid: the pid in question.
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 5ae7b4e6e8d6..0c5c61a095f6 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -169,122 +169,12 @@  static unsigned int get_next_freq(struct sugov_policy *sg_policy,
 	return cpufreq_driver_resolve_freq(policy, freq);
 }
 
-/*
- * This function computes an effective utilization for the given CPU, to be
- * used for frequency selection given the linear relation: f = u * f_max.
- *
- * The scheduler tracks the following metrics:
- *
- *   cpu_util_{cfs,rt,dl,irq}()
- *   cpu_bw_dl()
- *
- * Where the cfs,rt and dl util numbers are tracked with the same metric and
- * synchronized windows and are thus directly comparable.
- *
- * The cfs,rt,dl utilization are the running times measured with rq->clock_task
- * which excludes things like IRQ and steal-time. These latter are then accrued
- * in the irq utilization.
- *
- * The DL bandwidth number otoh is not a measured metric but a value computed
- * based on the task model parameters and gives the minimal utilization
- * required to meet deadlines.
- */
-unsigned long schedutil_cpu_util(int cpu, unsigned long util_cfs,
-				 unsigned long max, enum schedutil_type type,
-				 struct task_struct *p)
-{
-	unsigned long dl_util, util, irq;
-	struct rq *rq = cpu_rq(cpu);
-
-	if (!uclamp_is_used() &&
-	    type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt)) {
-		return max;
-	}
-
-	/*
-	 * Early check to see if IRQ/steal time saturates the CPU, can be
-	 * because of inaccuracies in how we track these -- see
-	 * update_irq_load_avg().
-	 */
-	irq = cpu_util_irq(rq);
-	if (unlikely(irq >= max))
-		return max;
-
-	/*
-	 * Because the time spend on RT/DL tasks is visible as 'lost' time to
-	 * CFS tasks and we use the same metric to track the effective
-	 * utilization (PELT windows are synchronized) we can directly add them
-	 * to obtain the CPU's actual utilization.
-	 *
-	 * CFS and RT utilization can be boosted or capped, depending on
-	 * utilization clamp constraints requested by currently RUNNABLE
-	 * tasks.
-	 * When there are no CFS RUNNABLE tasks, clamps are released and
-	 * frequency will be gracefully reduced with the utilization decay.
-	 */
-	util = util_cfs + cpu_util_rt(rq);
-	if (type == FREQUENCY_UTIL)
-		util = uclamp_rq_util_with(rq, util, p);
-
-	dl_util = cpu_util_dl(rq);
-
-	/*
-	 * For frequency selection we do not make cpu_util_dl() a permanent part
-	 * of this sum because we want to use cpu_bw_dl() later on, but we need
-	 * to check if the CFS+RT+DL sum is saturated (ie. no idle time) such
-	 * that we select f_max when there is no idle time.
-	 *
-	 * NOTE: numerical errors or stop class might cause us to not quite hit
-	 * saturation when we should -- something for later.
-	 */
-	if (util + dl_util >= max)
-		return max;
-
-	/*
-	 * OTOH, for energy computation we need the estimated running time, so
-	 * include util_dl and ignore dl_bw.
-	 */
-	if (type == ENERGY_UTIL)
-		util += dl_util;
-
-	/*
-	 * There is still idle time; further improve the number by using the
-	 * irq metric. Because IRQ/steal time is hidden from the task clock we
-	 * need to scale the task numbers:
-	 *
-	 *              max - irq
-	 *   U' = irq + --------- * U
-	 *                 max
-	 */
-	util = scale_irq_capacity(util, irq, max);
-	util += irq;
-
-	/*
-	 * Bandwidth required by DEADLINE must always be granted while, for
-	 * FAIR and RT, we use blocked utilization of IDLE CPUs as a mechanism
-	 * to gracefully reduce the frequency when no tasks show up for longer
-	 * periods of time.
-	 *
-	 * Ideally we would like to set bw_dl as min/guaranteed freq and util +
-	 * bw_dl as requested freq. However, cpufreq is not yet ready for such
-	 * an interface. So, we only do the latter for now.
-	 */
-	if (type == FREQUENCY_UTIL)
-		util += cpu_bw_dl(rq);
-
-	return min(max, util);
-}
-
 static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
 {
-	struct rq *rq = cpu_rq(sg_cpu->cpu);
-	unsigned long util = cpu_util_cfs(rq);
-	unsigned long max = arch_scale_cpu_capacity(sg_cpu->cpu);
-
-	sg_cpu->max = max;
-	sg_cpu->bw_dl = cpu_bw_dl(rq);
+	sg_cpu->max = arch_scale_cpu_capacity(sg_cpu->cpu);
+	sg_cpu->bw_dl = cpu_bw_dl(cpu_rq(sg_cpu->cpu));
 
-	return schedutil_cpu_util(sg_cpu->cpu, util, max, FREQUENCY_UTIL, NULL);
+	return sched_cpu_util(sg_cpu->cpu, FREQUENCY_UTIL, sg_cpu->max);
 }
 
 /**
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index aa4c6227cd6d..52e2d866e875 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6499,7 +6499,7 @@  compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
 		 * is already enough to scale the EM reported power
 		 * consumption at the (eventually clamped) cpu_capacity.
 		 */
-		sum_util += schedutil_cpu_util(cpu, util_cfs, cpu_cap,
+		sum_util += effective_cpu_util(cpu, util_cfs, cpu_cap,
 					       ENERGY_UTIL, NULL);
 
 		/*
@@ -6509,7 +6509,7 @@  compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
 		 * NOTE: in case RT tasks are running, by default the
 		 * FREQUENCY_UTIL's utilization can be max OPP.
 		 */
-		cpu_util = schedutil_cpu_util(cpu, util_cfs, cpu_cap,
+		cpu_util = effective_cpu_util(cpu, util_cfs, cpu_cap,
 					      FREQUENCY_UTIL, tsk);
 		max_util = max(max_util, cpu_util);
 	}
@@ -6607,7 +6607,7 @@  static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 			 * IOW, placing the task there would make the CPU
 			 * overutilized. Take uclamp into account to see how
 			 * much capacity we can get out of the CPU; this is
-			 * aligned with schedutil_cpu_util().
+			 * aligned with sched_cpu_util().
 			 */
 			util = uclamp_rq_util_with(cpu_rq(cpu), util, p);
 			if (!fits_capacity(util, cpu_cap))
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index df80bfcea92e..0f0439344eec 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2486,25 +2486,8 @@  static inline unsigned long capacity_orig_of(int cpu)
 }
 #endif
 
-/**
- * enum schedutil_type - CPU utilization type
- * @FREQUENCY_UTIL:	Utilization used to select frequency
- * @ENERGY_UTIL:	Utilization used during energy calculation
- *
- * The utilization signals of all scheduling classes (CFS/RT/DL) and IRQ time
- * need to be aggregated differently depending on the usage made of them. This
- * enum is used within schedutil_freq_util() to differentiate the types of
- * utilization expected by the callers, and adjust the aggregation accordingly.
- */
-enum schedutil_type {
-	FREQUENCY_UTIL,
-	ENERGY_UTIL,
-};
-
-#ifdef CONFIG_CPU_FREQ_GOV_SCHEDUTIL
-
-unsigned long schedutil_cpu_util(int cpu, unsigned long util_cfs,
-				 unsigned long max, enum schedutil_type type,
+unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
+				 unsigned long max, enum cpu_util_type type,
 				 struct task_struct *p);
 
 static inline unsigned long cpu_bw_dl(struct rq *rq)
@@ -2533,14 +2516,6 @@  static inline unsigned long cpu_util_rt(struct rq *rq)
 {
 	return READ_ONCE(rq->avg_rt.util_avg);
 }
-#else /* CONFIG_CPU_FREQ_GOV_SCHEDUTIL */
-static inline unsigned long schedutil_cpu_util(int cpu, unsigned long util_cfs,
-				 unsigned long max, enum schedutil_type type,
-				 struct task_struct *p)
-{
-	return 0;
-}
-#endif /* CONFIG_CPU_FREQ_GOV_SCHEDUTIL */
 
 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
 static inline unsigned long cpu_util_irq(struct rq *rq)