LKML Archive on lore.kernel.org
 help / color / Atom feed
From: skannan@codeaurora.org
To: Quentin Perret <quentin.perret@arm.com>
Cc: peterz@infradead.org, rjw@rjwysocki.net,
	linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	gregkh@linuxfoundation.org, mingo@redhat.com,
	dietmar.eggemann@arm.com, morten.rasmussen@arm.com,
	chris.redpath@arm.com, patrick.bellasi@arm.com,
	valentin.schneider@arm.com, vincent.guittot@linaro.org,
	thara.gopinath@linaro.org, viresh.kumar@linaro.org,
	tkjos@google.com, joel@joelfernandes.org, smuckle@google.com,
	adharmap@quicinc.com, skannan@quicinc.com,
	pkondeti@codeaurora.org, juri.lelli@redhat.com,
	edubezval@gmail.com, srinivas.pandruvada@linux.intel.com,
	currojerez@riseup.net, javi.merino@kernel.org,
	linux-pm-owner@vger.kernel.org
Subject: Re: [PATCH v5 10/14] sched/cpufreq: Refactor the utilization aggregation method
Date: Mon, 30 Jul 2018 12:35:27 -0700
Message-ID: <331552975e858911db66bc78c2c8e720@codeaurora.org> (raw)
In-Reply-To: <20180724122521.22109-11-quentin.perret@arm.com>

On 2018-07-24 05:25, Quentin Perret wrote:
> Schedutil aggregates the PELT signals of CFS, RT, DL and IRQ in order
> to decide which frequency to request. Energy Aware Scheduling (EAS)
> needs to be able to predict those requests to assess the energy impact
> of scheduling decisions. However, the PELT signals aggregation is only
> done in schedutil for now, hence making it hard to synchronize it with
> EAS.
> 
> To address this issue, introduce schedutil_freq_util() to perform the
> aforementioned aggregation and make it available to other parts of the
> scheduler. Since frequency selection and energy estimation still need
> to deal with RT and DL signals slightly differently, 
> schedutil_freq_util()
> is called with a different 'type' parameter in those two contexts, and
> returns an aggregated utilization signal accordingly.
> 
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Quentin Perret <quentin.perret@arm.com>
> ---
>  kernel/sched/cpufreq_schedutil.c | 86 +++++++++++++++++++++-----------
>  kernel/sched/sched.h             | 14 ++++++
>  2 files changed, 72 insertions(+), 28 deletions(-)
> 
> diff --git a/kernel/sched/cpufreq_schedutil.c 
> b/kernel/sched/cpufreq_schedutil.c
> index 810193c8e4cd..af86050edcf5 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -198,15 +198,15 @@ static unsigned int get_next_freq(struct
> sugov_policy *sg_policy,
>   * based on the task model parameters and gives the minimal 
> utilization
>   * required to meet deadlines.
>   */
> -static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
> +unsigned long schedutil_freq_util(int cpu, unsigned long util_cfs,
> +				  enum schedutil_type type)
>  {
> -	struct rq *rq = cpu_rq(sg_cpu->cpu);
> +	struct rq *rq = cpu_rq(cpu);
>  	unsigned long util, irq, max;
> 
> -	sg_cpu->max = max = arch_scale_cpu_capacity(NULL, sg_cpu->cpu);
> -	sg_cpu->bw_dl = cpu_bw_dl(rq);
> +	max = arch_scale_cpu_capacity(NULL, cpu);
> 
> -	if (rt_rq_is_runnable(&rq->rt))
> +	if (type == frequency_util && rt_rq_is_runnable(&rq->rt))
>  		return max;
> 
>  	/*
> @@ -224,20 +224,33 @@ static unsigned long sugov_get_util(struct
> sugov_cpu *sg_cpu)
>  	 * utilization (PELT windows are synchronized) we can directly add 
> them
>  	 * to obtain the CPU's actual utilization.
>  	 */
> -	util = cpu_util_cfs(rq);
> +	util = util_cfs;
>  	util += cpu_util_rt(rq);
> 
> -	/*
> -	 * 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 + cpu_util_dl(rq)) >= max)
> -		return max;
> +	if (type == frequency_util) {
> +		/*
> +		 * 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 + cpu_util_dl(rq)) >= max)
> +			return max;
> +	} else {
> +		/*
> +		 * OTOH, for energy computation we need the estimated
> +		 * running time, so include util_dl and ignore dl_bw.
> +		 */
> +		util += cpu_util_dl(rq);
> +		if (util >= max)
> +			return max;
> +	}

If it's going to be a different aggregation from what's done for 
frequency guidance, I don't see the point of having this inside 
schedutil. Why not keep it inside the scheduler files? Also, it seems 
weird to use a governor's code when it might not actually be in use. 
What if someone is using ondemand, conservative, performance, etc?

> 
>  	/*
>  	 * There is still idle time; further improve the number by using the
> @@ -252,17 +265,34 @@ static unsigned long sugov_get_util(struct
> sugov_cpu *sg_cpu)
>  	util /= 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.
> -	 */
> -	return min(max, util + sg_cpu->bw_dl);
> +	if (type == frequency_util) {
> +		/*
> +		 * 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.
> +		 */
> +		util += cpu_bw_dl(rq);
> +	}

Instead of all this indentation, can't you just return early without 
doing the code inside the if?

> +
> +	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);
> +
> +	sg_cpu->max = arch_scale_cpu_capacity(NULL, sg_cpu->cpu);
> +	sg_cpu->bw_dl = cpu_bw_dl(rq);
> +
> +	return schedutil_freq_util(sg_cpu->cpu, util, frequency_util);
>  }
> 
>  /**
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 6d08ccd1e7a4..51e7f113ee23 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2185,7 +2185,15 @@ static inline void cpufreq_update_util(struct
> rq *rq, unsigned int flags) {}
>  # define arch_scale_freq_invariant()	false
>  #endif
> 
> +enum schedutil_type {
> +	frequency_util,
> +	energy_util,
> +};

Please don't use lower case for enums. It's extremely confusing.

Thanks,
Saravana

  reply index

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-24 12:25 [PATCH v5 00/14] Energy Aware Scheduling Quentin Perret
2018-07-24 12:25 ` [PATCH v5 01/14] sched: Relocate arch_scale_cpu_capacity Quentin Perret
2018-07-24 12:25 ` [PATCH v5 02/14] sched/cpufreq: Factor out utilization to frequency mapping Quentin Perret
2018-07-24 12:25 ` [PATCH v5 03/14] PM: Introduce an Energy Model management framework Quentin Perret
2018-08-09 21:52   ` Rafael J. Wysocki
2018-08-10  8:15     ` Quentin Perret
2018-08-10  8:41       ` Rafael J. Wysocki
2018-08-10  9:12         ` Quentin Perret
2018-08-10 11:13           ` Rafael J. Wysocki
2018-08-10 12:30             ` Quentin Perret
2018-08-12  9:49               ` Rafael J. Wysocki
2018-07-24 12:25 ` [PATCH v5 04/14] PM / EM: Expose the Energy Model in sysfs Quentin Perret
2018-07-24 12:25 ` [PATCH v5 05/14] sched/topology: Reference the Energy Model of CPUs when available Quentin Perret
2018-07-24 12:25 ` [PATCH v5 06/14] sched/topology: Lowest energy aware balancing sched_domain level pointer Quentin Perret
2018-07-26 16:00   ` Valentin Schneider
2018-07-26 17:01     ` Quentin Perret
2018-07-24 12:25 ` [PATCH v5 07/14] sched/topology: Introduce sched_energy_present static key Quentin Perret
2018-07-24 12:25 ` [PATCH v5 08/14] sched/fair: Clean-up update_sg_lb_stats parameters Quentin Perret
2018-07-24 12:25 ` [PATCH v5 09/14] sched: Add over-utilization/tipping point indicator Quentin Perret
2018-08-02 12:26   ` Peter Zijlstra
2018-08-02 13:03     ` Quentin Perret
2018-08-02 13:08       ` Peter Zijlstra
2018-08-02 13:18         ` Quentin Perret
2018-08-02 13:48           ` Vincent Guittot
2018-08-02 14:14             ` Quentin Perret
2018-08-02 15:14               ` Vincent Guittot
2018-08-02 15:30                 ` Quentin Perret
2018-08-02 15:55                   ` Vincent Guittot
2018-08-02 16:00                     ` Quentin Perret
2018-08-02 16:07                       ` Vincent Guittot
2018-08-02 16:10                         ` Quentin Perret
2018-08-02 16:38                           ` Vincent Guittot
2018-08-02 16:59                             ` Quentin Perret
2018-08-03  7:48                               ` Vincent Guittot
2018-08-03  8:18                                 ` Quentin Perret
2018-08-03 13:49                                   ` Vincent Guittot
2018-08-03 14:21                                     ` Vincent Guittot
2018-08-03 15:55                                     ` Quentin Perret
2018-08-06  8:40                                       ` Vincent Guittot
2018-08-06  9:43                                         ` Quentin Perret
2018-08-06 10:45                                           ` Vincent Guittot
2018-08-06 11:02                                             ` Quentin Perret
2018-08-06 10:08                                         ` Dietmar Eggemann
2018-08-06 10:33                                           ` Vincent Guittot
2018-08-06 12:29                                             ` Dietmar Eggemann
2018-08-06 12:37                                               ` Vincent Guittot
2018-08-06 13:20                                                 ` Dietmar Eggemann
2018-08-09  9:30   ` Vincent Guittot
2018-08-09  9:38     ` Quentin Perret
2018-07-24 12:25 ` [PATCH v5 10/14] sched/cpufreq: Refactor the utilization aggregation method Quentin Perret
2018-07-30 19:35   ` skannan [this message]
2018-07-31  7:59     ` Quentin Perret
2018-07-31 19:31       ` skannan
2018-08-01  7:32         ` Rafael J. Wysocki
2018-08-01  8:23           ` Quentin Perret
2018-08-01  8:35             ` Rafael J. Wysocki
2018-08-01  9:23               ` Quentin Perret
2018-08-01  9:40                 ` Rafael J. Wysocki
2018-08-02 13:04                 ` Peter Zijlstra
2018-08-02 15:39                   ` Quentin Perret
2018-08-03 13:04                     ` Quentin Perret
2018-08-02 12:33     ` Peter Zijlstra
2018-08-02 12:45       ` Peter Zijlstra
2018-08-02 15:21         ` Quentin Perret
2018-08-02 17:36           ` Peter Zijlstra
2018-08-03 12:42             ` Quentin Perret
2018-07-24 12:25 ` [PATCH v5 11/14] sched/fair: Introduce an energy estimation helper function Quentin Perret
2018-07-24 12:25 ` [PATCH v5 12/14] sched/fair: Select an energy-efficient CPU on task wake-up Quentin Perret
2018-08-02 13:54   ` Peter Zijlstra
2018-08-02 16:21     ` Quentin Perret
2018-07-24 12:25 ` [PATCH v5 13/14] OPTIONAL: arch_topology: Start Energy Aware Scheduling Quentin Perret
2018-07-24 12:25 ` [PATCH v5 14/14] OPTIONAL: cpufreq: dt: Register an Energy Model Quentin Perret

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=331552975e858911db66bc78c2c8e720@codeaurora.org \
    --to=skannan@codeaurora.org \
    --cc=adharmap@quicinc.com \
    --cc=chris.redpath@arm.com \
    --cc=currojerez@riseup.net \
    --cc=dietmar.eggemann@arm.com \
    --cc=edubezval@gmail.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=javi.merino@kernel.org \
    --cc=joel@joelfernandes.org \
    --cc=juri.lelli@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pm-owner@vger.kernel.org \
    --cc=linux-pm@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=morten.rasmussen@arm.com \
    --cc=patrick.bellasi@arm.com \
    --cc=peterz@infradead.org \
    --cc=pkondeti@codeaurora.org \
    --cc=quentin.perret@arm.com \
    --cc=rjw@rjwysocki.net \
    --cc=skannan@quicinc.com \
    --cc=smuckle@google.com \
    --cc=srinivas.pandruvada@linux.intel.com \
    --cc=thara.gopinath@linaro.org \
    --cc=tkjos@google.com \
    --cc=valentin.schneider@arm.com \
    --cc=vincent.guittot@linaro.org \
    --cc=viresh.kumar@linaro.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org linux-kernel@archiver.kernel.org
	public-inbox-index lkml


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox