Re: [Eas-dev] [PATCH V2] cpufreq: schedutil: Redefine the rate_limit_us tunable

On Tue, Feb 21, 2017 at 5:45 AM, Viresh Kumar viresh.kumar@linaro.org wrote:

The rate_limit_us tunable is intended to reduce the possible overhead from running the schedutil governor. However, that overhead can be divided into two separate parts: the governor computations and the invocation of the scaling driver to set the CPU frequency. The latter is where the real overhead comes from. The former is much less expensive in terms of execution time and running it every time the governor callback is invoked by the scheduler, after rate_limit_us interval has passed since the last frequency update, would not be a problem.

For this reason, redefine the rate_limit_us tunable so that it means the minimum time that has to pass between two consecutive invocations of the scaling driver by the schedutil governor (to set the CPU frequency).

Signed-off-by: Viresh Kumar viresh.kumar@linaro.org

I'd prefer this to spend some time in linux-next before it goes into the mainline, so I will queue it up for 4.12 if no one objects by the end of the next week.

Thanks, Rafael

---

V1->V2: Update $subject and commit log (Rafael)

kernel/sched/cpufreq_schedutil.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index fd4659313640..306d97e7b57c 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -92,14 +92,13 @@ static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time, { struct cpufreq_policy *policy = sg_policy->policy;

•   sg_policy->last_freq_update_time = time;
  

•   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;
  

•           sg_policy->last_freq_update_time = time;
            next_freq = cpufreq_driver_fast_switch(policy, next_freq);
            if (next_freq == CPUFREQ_ENTRY_INVALID)
                    return;
  

@@ -108,6 +107,7 @@ static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time, trace_cpu_frequency(next_freq, smp_processor_id()); } else if (sg_policy->next_freq != next_freq) { sg_policy->next_freq = next_freq;

•           sg_policy->last_freq_update_time = time;
            sg_policy->work_in_progress = true;
            irq_work_queue(&sg_policy->irq_work);
    }
  

-- 2.7.1.410.g6faf27b