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Message-ID: <CAJZ5v0jcFNdYMXdaBDaTzyxCaPn9=q2YxUMqziEaprwiOm=5dA@mail.gmail.com>
Date: Thu, 19 May 2016 01:24:41 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Steve Muckle <steve.muckle@...aro.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
Morten Rasmussen <morten.rasmussen@....com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Juri Lelli <Juri.Lelli@....com>,
Patrick Bellasi <patrick.bellasi@....com>,
Michael Turquette <mturquette@...libre.com>,
Viresh Kumar <viresh.kumar@...aro.org>,
Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
Len Brown <lenb@...nel.org>
Subject: Re: [PATCH 2/5] cpufreq: schedutil: support scheduler cpufreq
callbacks on remote CPUs
On Mon, May 9, 2016 at 11:20 PM, Steve Muckle <steve.muckle@...aro.org> wrote:
> In preparation for the scheduler cpufreq callback happening on remote
> CPUs, add support for this in schedutil.
>
> Schedutil currently requires the callback occur on the CPU being
> updated in order to support fast frequency switches. Remove this
> limitation by checking for the current CPU being outside the target
> CPU's cpufreq policy and if this is the case, enqueuing an irq_work on
> the target CPU. The irq_work for schedutil is modified to carry out a
> fast frequency switch if that is enabled for the policy.
>
> If the callback occurs on a CPU within the target CPU's policy, the
> transition is carried out on the local CPU.
>
> Signed-off-by: Steve Muckle <smuckle@...aro.org>
> ---
> kernel/sched/cpufreq_schedutil.c | 86 ++++++++++++++++++++++++++++++----------
> 1 file changed, 65 insertions(+), 21 deletions(-)
>
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 154ae3a51e86..c81f9432f520 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -76,27 +76,61 @@ static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
> return delta_ns >= sg_policy->freq_update_delay_ns;
> }
>
> -static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
> +static void sugov_fast_switch(struct sugov_policy *sg_policy, int cpu,
> + unsigned int next_freq)
> +{
> + struct cpufreq_policy *policy = sg_policy->policy;
> +
> + next_freq = cpufreq_driver_fast_switch(policy, next_freq);
> + if (next_freq == CPUFREQ_ENTRY_INVALID)
> + return;
> +
> + policy->cur = next_freq;
> + trace_cpu_frequency(next_freq, cpu);
> +}
> +
> +#ifdef CONFIG_SMP
schedutil depends on CONFIG_SMP now, so that's not necessary at least
for the time being.
> +static inline bool sugov_queue_remote_callback(struct sugov_policy *sg_policy,
> + int cpu)
> +{
> + struct cpufreq_policy *policy = sg_policy->policy;
> +
> + if (!cpumask_test_cpu(smp_processor_id(), policy->cpus)) {
This check is overkill for policies that aren't shared (and we have a
special case for them already).
> + sg_policy->work_in_progress = true;
> + irq_work_queue_on(&sg_policy->irq_work, cpu);
> + return true;
> + }
> +
> + return false;
> +}
> +#else
> +static inline bool sugov_queue_remote_callback(struct sugov_policy *sg_policy,
> + int cpu)
> +{
> + return false;
> +}
> +#endif
> +
> +static void sugov_update_commit(struct sugov_cpu *sg_cpu, int cpu, u64 time,
It looks like you might pass hook here instead of the sg_cpu, cpu pair.
> unsigned int next_freq)
> {
> + struct sugov_policy *sg_policy = sg_cpu->sg_policy;
> struct cpufreq_policy *policy = sg_policy->policy;
>
> sg_policy->last_freq_update_time = time;
>
> + if (sg_policy->next_freq == next_freq) {
> + trace_cpu_frequency(policy->cur, cpu);
> + return;
> + }
There was a reason why I put the above under the fast_switch_enabled
branch and it was because this check/trace is not necessary otherwise.
> + sg_policy->next_freq = next_freq;
> +
> + if (sugov_queue_remote_callback(sg_policy, cpu))
> + return;
> +
> if (policy->fast_switch_enabled) {
> - if (sg_policy->next_freq == next_freq) {
> - trace_cpu_frequency(policy->cur, smp_processor_id());
> - return;
> - }
> - sg_policy->next_freq = next_freq;
> - next_freq = cpufreq_driver_fast_switch(policy, next_freq);
> - if (next_freq == CPUFREQ_ENTRY_INVALID)
> - return;
> -
> - policy->cur = next_freq;
> - trace_cpu_frequency(next_freq, smp_processor_id());
> - } else if (sg_policy->next_freq != next_freq) {
> - sg_policy->next_freq = next_freq;
> + sugov_fast_switch(sg_policy, cpu, next_freq);
> + } else {
> sg_policy->work_in_progress = true;
> irq_work_queue(&sg_policy->irq_work);
> }
> @@ -142,12 +176,13 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
>
> next_f = util == ULONG_MAX ? policy->cpuinfo.max_freq :
> get_next_freq(policy, util, max);
> - sugov_update_commit(sg_policy, time, next_f);
> + sugov_update_commit(sg_cpu, hook->cpu, time, next_f);
> }
>
> -static unsigned int sugov_next_freq_shared(struct sugov_policy *sg_policy,
> +static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu,
> unsigned long util, unsigned long max)
> {
> + struct sugov_policy *sg_policy = sg_cpu->sg_policy;
> struct cpufreq_policy *policy = sg_policy->policy;
> unsigned int max_f = policy->cpuinfo.max_freq;
> u64 last_freq_update_time = sg_policy->last_freq_update_time;
> @@ -161,10 +196,10 @@ static unsigned int sugov_next_freq_shared(struct sugov_policy *sg_policy,
> unsigned long j_util, j_max;
> s64 delta_ns;
>
> - if (j == smp_processor_id())
> + j_sg_cpu = &per_cpu(sugov_cpu, j);
> + if (j_sg_cpu == sg_cpu)
> continue;
>
> - j_sg_cpu = &per_cpu(sugov_cpu, j);
> /*
> * If the CPU utilization was last updated before the previous
> * frequency update and the time elapsed between the last update
> @@ -204,8 +239,8 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
> sg_cpu->last_update = time;
>
> if (sugov_should_update_freq(sg_policy, time)) {
> - next_f = sugov_next_freq_shared(sg_policy, util, max);
> - sugov_update_commit(sg_policy, time, next_f);
> + next_f = sugov_next_freq_shared(sg_cpu, util, max);
> + sugov_update_commit(sg_cpu, hook->cpu, time, next_f);
> }
>
> raw_spin_unlock(&sg_policy->update_lock);
> @@ -226,9 +261,18 @@ static void sugov_work(struct work_struct *work)
> static void sugov_irq_work(struct irq_work *irq_work)
> {
> struct sugov_policy *sg_policy;
> + struct cpufreq_policy *policy;
>
> sg_policy = container_of(irq_work, struct sugov_policy, irq_work);
> - schedule_work_on(smp_processor_id(), &sg_policy->work);
> + policy = sg_policy->policy;
> +
> + if (policy->fast_switch_enabled) {
> + sugov_fast_switch(sg_policy, smp_processor_id(),
> + sg_policy->next_freq);
> + sg_policy->work_in_progress = false;
> + } else {
> + schedule_work_on(smp_processor_id(), &sg_policy->work);
> + }
> }
>
> /************************** sysfs interface ************************/
> --
> 2.4.10
>
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