On Monday, July 27, 2015 05:58:11 PM Viresh Kumar wrote:
> Currently update_sampling_rate() runs over each online CPU and
> cancels/queues work on it. Its very inefficient for the case where a
> single policy manages multiple CPUs, as they can be processed together.
>
> Also drop the unnecessary cancel_delayed_work_sync() as we are doing a
> mod_delayed_work_on() in gov_queue_work(), which will take care of
> pending works for us.
>
> Signed-off-by: Viresh Kumar <viresh.ku...@linaro.org>
> ---
> drivers/cpufreq/cpufreq_ondemand.c | 31 ++++++++++++++++++-------------
> 1 file changed, 18 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq_ondemand.c
> b/drivers/cpufreq/cpufreq_ondemand.c
> index f1551fc7b4fd..a6f579e40ce2 100644
> --- a/drivers/cpufreq/cpufreq_ondemand.c
> +++ b/drivers/cpufreq/cpufreq_ondemand.c
> @@ -247,40 +247,45 @@ static void update_sampling_rate(struct dbs_data
> *dbs_data,
> unsigned int new_rate)
> {
> struct od_dbs_tuners *od_tuners = dbs_data->tuners;
> + struct cpufreq_policy *policy;
> + struct od_cpu_dbs_info_s *dbs_info;
> + unsigned long next_sampling, appointed_at;
> + struct cpumask cpumask;
> int cpu;
>
> + cpumask_copy(&cpumask, cpu_online_mask);
> +
> od_tuners->sampling_rate = new_rate = max(new_rate,
> dbs_data->min_sampling_rate);
>
> - for_each_online_cpu(cpu) {
> - struct cpufreq_policy *policy;
> - struct od_cpu_dbs_info_s *dbs_info;
> - unsigned long next_sampling, appointed_at;
> -
> + for_each_cpu(cpu, &cpumask) {
> policy = cpufreq_cpu_get(cpu);
> if (!policy)
> continue;
> +
> + /* clear all CPUs of this policy */
> + cpumask_andnot(&cpumask, &cpumask, policy->cpus);
Well, this is not exactly straightforward, but should work.
> +
> if (policy->governor != &cpufreq_gov_ondemand) {
> cpufreq_cpu_put(policy);
> continue;
> }
> +
> dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
> cpufreq_cpu_put(policy);
>
> - if (!delayed_work_pending(&dbs_info->cdbs.dwork))
> + /* Make sure the work is not canceled on policy->cpus */
I'm not sure what scenario can lead to that. Care to explain?
> + if (!dbs_info->cdbs.shared->policy)
> continue;
>
> next_sampling = jiffies + usecs_to_jiffies(new_rate);
> appointed_at = dbs_info->cdbs.dwork.timer.expires;
For that to work we always need to do stuff for policy->cpus in sync.
Do we?
> - if (time_before(next_sampling, appointed_at)) {
> - cancel_delayed_work_sync(&dbs_info->cdbs.dwork);
> -
> - gov_queue_work(dbs_data, policy,
> - usecs_to_jiffies(new_rate),
> - cpumask_of(cpu));
> + if (!time_before(next_sampling, appointed_at))
> + continue;
>
> - }
> + gov_queue_work(dbs_data, policy, usecs_to_jiffies(new_rate),
> + policy->cpus);
> }
> }
>
>
Thanks,
Rafael
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