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Date: Fri, 22 Mar 2013 00:54:58 +0100
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Stratos Karafotis <stratosk@...aphore.gr>, 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 Friday, March 01, 2013 09:18:08 AM Viresh Kumar wrote:
> 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>
Applied to linux-pm.git/bleeding-edge and will be moved to linux-next if there
are no build problems in the bleeding-edge branch.
Thanks,
Rafael
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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