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Message-ID: <512F8C7C.2020101@semaphore.gr>
Date: Thu, 28 Feb 2013 18:57:32 +0200
From: Stratos Karafotis <stratosk@...aphore.gr>
To: Viresh Kumar <viresh.kumar@...aro.org>
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
Hi Viresh,
On 02/28/2013 08:58 AM, Viresh Kumar wrote:
> I have really spent some 10-15 minutes reviewing this patch as initially it
> looked to me like something is missing here and calculations are going wrong.
>
> But it was fine :)
Thanks for you review.
>> diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
>> index f3eb26c..46be2c4 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,
>> {
>
>> + /* we need to re-evaluate prev_cpu_idle */
>> + for_each_online_cpu(j) {
>> + struct od_cpu_dbs_info_s *dbs_info;
>> + dbs_info = &per_cpu(od_cpu_dbs_info, j);
>
> Probably squash above two lines and give a blank line after it.
>
>> + dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
>> + &dbs_info->cdbs.prev_cpu_wall, od_tuners.io_is_busy);
>> + }
>> return count;
>> }
>
> And after that add my:
>
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
>
Bellow V2 with your suggestion included.
Regards,
Stratos
----------------8<----------------------
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];
--
1.8.1.2
--
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