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Message-ID: <CAKohponkj++4AkW__i7vWykURkAkgiHGLMX973KWMjQw9sTQYg@mail.gmail.com>
Date: Fri, 1 Mar 2013 09:18:08 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Stratos Karafotis <stratosk@...aphore.gr>
Cc: "Rafael J. Wysocki" <rjw@...k.pl>, cpufreq@...r.kernel.org,
linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 linux-next] cpufreq: governors: Calculate iowait time
only when necessary
On 28 February 2013 22:27, Stratos Karafotis <stratosk@...aphore.gr> wrote:
> Currently we always calculate the CPU iowait time and add it to idle time.
> If we are in ondemand and we use io_is_busy, we re-calculate iowait time
> and we subtract it from idle time.
>
> With this patch iowait time is calculated only when necessary avoiding
> the double call to get_cpu_iowait_time_us. We use a parameter in
> function get_cpu_idle_time to distinguish when the iowait time will be
> added to idle time or not, without the need of keeping the prev_io_wait.
>
> Signed-off-by: Stratos Karafotis <stratosk@...aphore.gr>
> ---
> drivers/cpufreq/cpufreq_conservative.c | 2 +-
> drivers/cpufreq/cpufreq_governor.c | 46 +++++++++++++---------------------
> drivers/cpufreq/cpufreq_governor.h | 3 +--
> drivers/cpufreq/cpufreq_ondemand.c | 11 +++++++-
> 4 files changed, 29 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c
> index 4fd0006..dfe652c 100644
> --- a/drivers/cpufreq/cpufreq_conservative.c
> +++ b/drivers/cpufreq/cpufreq_conservative.c
> @@ -242,7 +242,7 @@ static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
> struct cs_cpu_dbs_info_s *dbs_info;
> dbs_info = &per_cpu(cs_cpu_dbs_info, j);
> dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
> - &dbs_info->cdbs.prev_cpu_wall);
> + &dbs_info->cdbs.prev_cpu_wall, 0);
> if (cs_tuners.ignore_nice)
> dbs_info->cdbs.prev_cpu_nice =
> kcpustat_cpu(j).cpustat[CPUTIME_NICE];
> diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
> index 5a76086..a322bda 100644
> --- a/drivers/cpufreq/cpufreq_governor.c
> +++ b/drivers/cpufreq/cpufreq_governor.c
> @@ -50,13 +50,13 @@ static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
> return cputime_to_usecs(idle_time);
> }
>
> -u64 get_cpu_idle_time(unsigned int cpu, u64 *wall)
> +u64 get_cpu_idle_time(unsigned int cpu, u64 *wall, int io_busy)
> {
> u64 idle_time = get_cpu_idle_time_us(cpu, NULL);
>
> if (idle_time == -1ULL)
> return get_cpu_idle_time_jiffy(cpu, wall);
> - else
> + else if (!io_busy)
> idle_time += get_cpu_iowait_time_us(cpu, wall);
>
> return idle_time;
> @@ -83,13 +83,22 @@ void dbs_check_cpu(struct dbs_data *dbs_data, int cpu)
> /* Get Absolute Load (in terms of freq for ondemand gov) */
> for_each_cpu(j, policy->cpus) {
> struct cpu_dbs_common_info *j_cdbs;
> - u64 cur_wall_time, cur_idle_time, cur_iowait_time;
> - unsigned int idle_time, wall_time, iowait_time;
> + u64 cur_wall_time, cur_idle_time;
> + unsigned int idle_time, wall_time;
> unsigned int load;
> + int io_busy = 0;
>
> j_cdbs = dbs_data->get_cpu_cdbs(j);
>
> - cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
> + /*
> + * For the purpose of ondemand, waiting for disk IO is
> + * an indication that you're performance critical, and
> + * not that the system is actually idle. So do not add
> + * the iowait time to the cpu idle time.
> + */
> + if (dbs_data->governor == GOV_ONDEMAND)
> + io_busy = od_tuners->io_is_busy;
> + cur_idle_time = get_cpu_idle_time(j, &cur_wall_time, io_busy);
>
> wall_time = (unsigned int)
> (cur_wall_time - j_cdbs->prev_cpu_wall);
> @@ -117,29 +126,6 @@ void dbs_check_cpu(struct dbs_data *dbs_data, int cpu)
> idle_time += jiffies_to_usecs(cur_nice_jiffies);
> }
>
> - if (dbs_data->governor == GOV_ONDEMAND) {
> - struct od_cpu_dbs_info_s *od_j_dbs_info =
> - dbs_data->get_cpu_dbs_info_s(cpu);
> -
> - cur_iowait_time = get_cpu_iowait_time_us(j,
> - &cur_wall_time);
> - if (cur_iowait_time == -1ULL)
> - cur_iowait_time = 0;
> -
> - iowait_time = (unsigned int) (cur_iowait_time -
> - od_j_dbs_info->prev_cpu_iowait);
> - od_j_dbs_info->prev_cpu_iowait = cur_iowait_time;
> -
> - /*
> - * For the purpose of ondemand, waiting for disk IO is
> - * an indication that you're performance critical, and
> - * not that the system is actually idle. So subtract the
> - * iowait time from the cpu idle time.
> - */
> - if (od_tuners->io_is_busy && idle_time >= iowait_time)
> - idle_time -= iowait_time;
> - }
> -
> if (unlikely(!wall_time || wall_time < idle_time))
> continue;
>
> @@ -207,6 +193,7 @@ int cpufreq_governor_dbs(struct dbs_data *dbs_data,
> struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
> struct cpu_dbs_common_info *cpu_cdbs;
> unsigned int *sampling_rate, latency, ignore_nice, j, cpu = policy->cpu;
> + int io_busy = 0;
> int rc;
>
> cpu_cdbs = dbs_data->get_cpu_cdbs(cpu);
> @@ -221,6 +208,7 @@ int cpufreq_governor_dbs(struct dbs_data *dbs_data,
> sampling_rate = &od_tuners->sampling_rate;
> ignore_nice = od_tuners->ignore_nice;
> od_ops = dbs_data->gov_ops;
> + io_busy = od_tuners->io_is_busy;
> }
>
> switch (event) {
> @@ -237,7 +225,7 @@ int cpufreq_governor_dbs(struct dbs_data *dbs_data,
> j_cdbs->cpu = j;
> j_cdbs->cur_policy = policy;
> j_cdbs->prev_cpu_idle = get_cpu_idle_time(j,
> - &j_cdbs->prev_cpu_wall);
> + &j_cdbs->prev_cpu_wall, io_busy);
> if (ignore_nice)
> j_cdbs->prev_cpu_nice =
> kcpustat_cpu(j).cpustat[CPUTIME_NICE];
> diff --git a/drivers/cpufreq/cpufreq_governor.h b/drivers/cpufreq/cpufreq_governor.h
> index d2ac911..534dfae 100644
> --- a/drivers/cpufreq/cpufreq_governor.h
> +++ b/drivers/cpufreq/cpufreq_governor.h
> @@ -87,7 +87,6 @@ struct cpu_dbs_common_info {
>
> struct od_cpu_dbs_info_s {
> struct cpu_dbs_common_info cdbs;
> - u64 prev_cpu_iowait;
> struct cpufreq_frequency_table *freq_table;
> unsigned int freq_lo;
> unsigned int freq_lo_jiffies;
> @@ -169,7 +168,7 @@ static inline int delay_for_sampling_rate(unsigned int sampling_rate)
> return delay;
> }
>
> -u64 get_cpu_idle_time(unsigned int cpu, u64 *wall);
> +u64 get_cpu_idle_time(unsigned int cpu, u64 *wall, int io_busy);
> void dbs_check_cpu(struct dbs_data *dbs_data, int cpu);
> bool need_load_eval(struct cpu_dbs_common_info *cdbs,
> unsigned int sampling_rate);
> diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
> index f3eb26c..74dd3ae 100644
> --- a/drivers/cpufreq/cpufreq_ondemand.c
> +++ b/drivers/cpufreq/cpufreq_ondemand.c
> @@ -339,11 +339,20 @@ static ssize_t store_io_is_busy(struct kobject *a, struct attribute *b,
> {
> unsigned int input;
> int ret;
> + unsigned int j;
>
> ret = sscanf(buf, "%u", &input);
> if (ret != 1)
> return -EINVAL;
> od_tuners.io_is_busy = !!input;
> +
> + /* we need to re-evaluate prev_cpu_idle */
> + for_each_online_cpu(j) {
> + struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
> + j);
> + dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
> + &dbs_info->cdbs.prev_cpu_wall, od_tuners.io_is_busy);
> + }
> return count;
> }
>
> @@ -411,7 +420,7 @@ static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
> struct od_cpu_dbs_info_s *dbs_info;
> dbs_info = &per_cpu(od_cpu_dbs_info, j);
> dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
> - &dbs_info->cdbs.prev_cpu_wall);
> + &dbs_info->cdbs.prev_cpu_wall, od_tuners.io_is_busy);
> if (od_tuners.ignore_nice)
> dbs_info->cdbs.prev_cpu_nice =
> kcpustat_cpu(j).cpustat[CPUTIME_NICE];
Acked-by: Viresh Kumar <viresh.kumar@...aro.,org>
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