From: peterz@infradead.org (Peter Zijlstra)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v7 5/7] sched: get CPU's usage statistic
Date: Thu, 9 Oct 2014 13:36:14 +0200 [thread overview]
Message-ID: <20141009113614.GP4750@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <1412684017-16595-6-git-send-email-vincent.guittot@linaro.org>
On Tue, Oct 07, 2014 at 02:13:35PM +0200, Vincent Guittot wrote:
> Monitor the usage level of each group of each sched_domain level. The usage is
> the amount of cpu_capacity that is currently used on a CPU or group of CPUs.
> We use the utilization_load_avg to evaluate the usage level of each group.
>
> The utilization_avg_contrib only takes into account the running time but not
> the uArch so the utilization_load_avg is in the range [0..SCHED_LOAD_SCALE]
> to reflect the running load on the CPU. We have to scale the utilization with
> the capacity of the CPU to get the usage of the latter. The usage can then be
> compared with the available capacity.
You say cpu_capacity, but in actual fact you use capacity_orig and fail
to justify/clarify this.
> The frequency scaling invariance is not taken into account in this patchset,
> it will be solved in another patchset
Maybe explain what the specific invariance issue is that is skipped over
for now.
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> ---
> kernel/sched/fair.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index d3e9067..7364ed4 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4551,6 +4551,17 @@ static int select_idle_sibling(struct task_struct *p, int target)
> return target;
> }
>
> +static int get_cpu_usage(int cpu)
> +{
> + unsigned long usage = cpu_rq(cpu)->cfs.utilization_load_avg;
> + unsigned long capacity = capacity_orig_of(cpu);
> +
> + if (usage >= SCHED_LOAD_SCALE)
> + return capacity + 1;
Like Morten I'm confused by that +1 thing.
> +
> + return (usage * capacity) >> SCHED_LOAD_SHIFT;
> +}
A comment with that function that it returns capacity units might
clarify shift confusion Morten raised the other day.
next prev parent reply other threads:[~2014-10-09 11:36 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-07 12:13 [PATCH v7 0/7] sched: consolidation of cpu_capacity Vincent Guittot
2014-10-07 12:13 ` [PATCH v7 1/7] sched: add per rq cpu_capacity_orig Vincent Guittot
2014-10-07 12:13 ` [PATCH v7 2/7] sched: move cfs task on a CPU with higher capacity Vincent Guittot
2014-10-09 11:23 ` Peter Zijlstra
2014-10-09 14:59 ` Vincent Guittot
2014-10-09 15:30 ` Peter Zijlstra
2014-10-10 7:46 ` Vincent Guittot
2014-10-07 12:13 ` [PATCH v7 3/7] sched: add utilization_avg_contrib Vincent Guittot
2014-10-08 17:04 ` Dietmar Eggemann
2014-10-07 12:13 ` [PATCH 4/7] sched: Track group sched_entity usage contributions Vincent Guittot
2014-10-07 20:15 ` bsegall at google.com
2014-10-08 7:16 ` Vincent Guittot
2014-10-08 11:13 ` Morten Rasmussen
2014-10-07 12:13 ` [PATCH v7 5/7] sched: get CPU's usage statistic Vincent Guittot
2014-10-09 11:36 ` Peter Zijlstra [this message]
2014-10-09 13:57 ` Vincent Guittot
2014-10-09 15:12 ` Peter Zijlstra
2014-10-10 14:38 ` Vincent Guittot
2014-10-07 12:13 ` [PATCH v7 6/7] sched: replace capacity_factor by usage Vincent Guittot
2014-10-09 12:16 ` Peter Zijlstra
2014-10-09 14:18 ` Vincent Guittot
2014-10-09 15:18 ` Peter Zijlstra
2014-10-10 7:17 ` Vincent Guittot
2014-10-10 7:18 ` Vincent Guittot
2014-11-23 1:03 ` Wanpeng Li
2014-11-24 10:16 ` Vincent Guittot
2014-10-09 14:16 ` Peter Zijlstra
2014-10-09 14:28 ` Vincent Guittot
2014-10-09 14:58 ` Peter Zijlstra
2014-10-21 7:38 ` Vincent Guittot
2014-10-07 12:13 ` [PATCH v7 7/7] sched: add SD_PREFER_SIBLING for SMT level Vincent Guittot
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