From: Stratos Karafotis <stratosk@semaphore.gr>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>,
cpufreq@vger.kernel.org, linux-pm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 linux-next] cpufreq: governors: Calculate iowait time only when necessary
Date: Thu, 28 Feb 2013 18:57:32 +0200 [thread overview]
Message-ID: <512F8C7C.2020101@semaphore.gr> (raw)
In-Reply-To: <CAOh2x==vxM+qoebcUGNca50oeszwnqSfSzVPSEOyS6GKENudeg@mail.gmail.com>
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@linaro.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@semaphore.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
next prev parent reply other threads:[~2013-02-28 16:57 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-27 17:44 [PATCH linux-next] cpufreq: governors: Calculate iowait time only when necessary Stratos Karafotis
2013-02-28 6:58 ` Viresh Kumar
2013-02-28 16:57 ` Stratos Karafotis [this message]
2013-03-01 3:48 ` [PATCH v2 " Viresh Kumar
2013-03-21 23:54 ` Rafael J. Wysocki
2013-03-22 7:12 ` Stratos Karafotis
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=512F8C7C.2020101@semaphore.gr \
--to=stratosk@semaphore.gr \
--cc=cpufreq@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=rjw@sisk.pl \
--cc=viresh.kumar@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.