Re: [PATCH v2 linux-next] cpufreq: ondemand: Calculate gradient ofCPU load to early increase frequency

From: Stratos Karafotis
Date: Thu Feb 21 2013 - 06:31:59 EST

Hi Viresh,

Thank you very much for your review and your suggestions.

On 02/21/2013 06:59 AM, Viresh Kumar wrote:
> Sorry for this but i already have a patchset which has changed these files
> to some extent. Can you please rebase over them? Actually my patchset
> is already accepted, its just that rafael didn't wanted to have them for 3.9.
>
> http://git.linaro.org/gitweb?p=people/vireshk/linux.git;a=shortlog;h=refs/heads/cpufreq-for-3.10

No problem. I rebased the patch over your tree.

> So, probably you just don't need this tunable: early_differential.
> Rather just increase the frequency without doing this calculation:
>
> if (load_freq > od_tuners.up_threshold * policy->cur) {

I agree with your suggestion. This is simpler approach. So, if the gradient is greater than
grad_up_threshold we increase frequency immediately. i.e.

if previous load was 10 and current load is 65 the gradient will be 55 (> grad_up_theshold)
and we increase frequency

>> + if (od_tuners.early_demand) {
>> + if (load_freq > dbs_info->prev_load_freq) {
>
> && (load_freq < od_tuners.up_threshold * policy->cur) ??

In my opinion this is not necessary. If load_freq is greater, then we have to increase
frequency in anyway.

>
>> +show_one(od, early_demand, early_demand);
>
> What about making other two tunables rw?
>

Of course. I added the grad_up_threshold.

Following patch v2.

Thanks again,
Stratos

------------------------8<----------------------------------------------
Instead of checking only the absolute value of CPU load_freq to increase
frequency, we detect forthcoming CPU load rise and increase frequency
earlier.

Every sampling rate, we calculate the gradient of load_freq. If it is
too steep we assume that the load most probably will go over
up_threshold in next iteration(s) and we increase frequency immediately.

New tuners are introduced:
- early_demand: to enable this functionality (disabled by default).
- grad_up_threshold: over this gradient of load we will increase
frequency immediately.

Signed-off-by: Stratos Karafotis <stratosk@xxxxxxxxxxxx>
---
drivers/cpufreq/cpufreq_governor.c | 1 +
drivers/cpufreq/cpufreq_governor.h | 6 +++-
drivers/cpufreq/cpufreq_ondemand.c | 72 ++++++++++++++++++++++++++++++++++----
3 files changed, 72 insertions(+), 7 deletions(-)

diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index 7722505..e737aa9 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c
@@ -322,6 +322,7 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy,
} else {
od_dbs_info->rate_mult = 1;
od_dbs_info->sample_type = OD_NORMAL_SAMPLE;
+ od_dbs_info->prev_load_freq = 0;
od_ops->powersave_bias_init_cpu(cpu);
}

diff --git a/drivers/cpufreq/cpufreq_governor.h b/drivers/cpufreq/cpufreq_governor.h
index 6301790..c9a237a 100644
--- a/drivers/cpufreq/cpufreq_governor.h
+++ b/drivers/cpufreq/cpufreq_governor.h
@@ -96,6 +96,7 @@ struct od_cpu_dbs_info_s {
unsigned int freq_hi_jiffies;
unsigned int rate_mult;
unsigned int sample_type:1;
+ unsigned int prev_load_freq;
};

struct cs_cpu_dbs_info_s {
@@ -114,6 +115,8 @@ struct od_dbs_tuners {
unsigned int adj_up_threshold;
unsigned int powersave_bias;
unsigned int io_is_busy;
+ unsigned int grad_up_threshold;
+ unsigned int early_demand;
};

struct cs_dbs_tuners {
@@ -160,7 +163,8 @@ struct od_ops {
void (*powersave_bias_init_cpu)(int cpu);
unsigned int (*powersave_bias_target)(struct cpufreq_policy *policy,
unsigned int freq_next, unsigned int relation);
- void (*freq_increase)(struct cpufreq_policy *p, unsigned int freq);
+ void (*freq_increase)(struct od_cpu_dbs_info_s *dbs_info,
+ struct cpufreq_policy *p, unsigned int freq);
};

struct cs_ops {
diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index c5fd794..4c948af 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -31,6 +31,7 @@
#define DEF_FREQUENCY_DOWN_DIFFERENTIAL (10)
#define DEF_FREQUENCY_UP_THRESHOLD (80)
#define DEF_SAMPLING_DOWN_FACTOR (1)
+#define DEF_GRAD_UP_THRESHOLD (50)
#define MAX_SAMPLING_DOWN_FACTOR (100000)
#define MICRO_FREQUENCY_DOWN_DIFFERENTIAL (3)
#define MICRO_FREQUENCY_UP_THRESHOLD (95)
@@ -139,11 +140,16 @@ static void ondemand_powersave_bias_init(void)
}
}

-static void dbs_freq_increase(struct cpufreq_policy *p, unsigned int freq)
+static void dbs_freq_increase(struct od_cpu_dbs_info_s *dbs_info,
+ struct cpufreq_policy *p, unsigned int freq)
{
struct dbs_data *dbs_data = p->governor_data;
struct od_dbs_tuners *od_tuners = dbs_data->tuners;

+ /* If switching to max speed, apply sampling_down_factor */
+ if (p->cur < p->max)
+ dbs_info->rate_mult = od_tuners->sampling_down_factor;
+
if (od_tuners->powersave_bias)
freq = powersave_bias_target(p, freq, CPUFREQ_RELATION_H);
else if (p->cur == p->max)
@@ -168,16 +174,29 @@ static void od_check_cpu(int cpu, unsigned int load_freq)
struct cpufreq_policy *policy = dbs_info->cdbs.cur_policy;
struct dbs_data *dbs_data = policy->governor_data;
struct od_dbs_tuners *od_tuners = dbs_data->tuners;
+ unsigned int prev_load_freq;

dbs_info->freq_lo = 0;

+ /*
+ * Calculate the gradient of load_freq. If it is too steep we assume
+ * that the load will go over up_threshold in next iteration(s) and
+ * we increase the frequency immediately
+ */
+ if (od_tuners->early_demand) {
+ prev_load_freq = dbs_info->prev_load_freq;
+ dbs_info->prev_load_freq = load_freq;
+
+ if (load_freq > prev_load_freq && (load_freq - prev_load_freq >
+ od_tuners->grad_up_threshold * policy->cur)) {
+ dbs_freq_increase(dbs_info, policy, policy->max);
+ return;
+ }
+ }
+
/* Check for frequency increase */
if (load_freq > od_tuners->up_threshold * policy->cur) {
- /* If switching to max speed, apply sampling_down_factor */
- if (policy->cur < policy->max)
- dbs_info->rate_mult =
- od_tuners->sampling_down_factor;
- dbs_freq_increase(policy, policy->max);
+ dbs_freq_increase(dbs_info, policy, policy->max);
return;
}

@@ -445,12 +464,47 @@ static ssize_t store_powersave_bias(struct cpufreq_policy *policy,
return count;
}

+static ssize_t store_grad_up_threshold(struct cpufreq_policy *policy,
+ const char *buf, size_t count)
+{
+ struct dbs_data *dbs_data = policy->governor_data;
+ struct od_dbs_tuners *od_tuners = dbs_data->tuners;
+ unsigned int input;
+ int ret;
+ ret = sscanf(buf, "%u", &input);
+
+ if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
+ input < MIN_FREQUENCY_UP_THRESHOLD) {
+ return -EINVAL;
+ }
+
+ od_tuners->grad_up_threshold = input;
+ return count;
+}
+
+static ssize_t store_early_demand(struct cpufreq_policy *policy,
+ const char *buf, size_t count)
+{
+ struct dbs_data *dbs_data = policy->governor_data;
+ struct od_dbs_tuners *od_tuners = dbs_data->tuners;
+ unsigned int input;
+ int ret;
+
+ ret = sscanf(buf, "%u", &input);
+ if (ret != 1)
+ return -EINVAL;
+ od_tuners->early_demand = !!input;
+ return count;
+}
+
show_one(od, sampling_rate, sampling_rate);
show_one(od, io_is_busy, io_is_busy);
show_one(od, up_threshold, up_threshold);
show_one(od, sampling_down_factor, sampling_down_factor);
show_one(od, ignore_nice, ignore_nice);
show_one(od, powersave_bias, powersave_bias);
+show_one(od, grad_up_threshold, grad_up_threshold);
+show_one(od, early_demand, early_demand);
declare_show_sampling_rate_min();

cpufreq_freq_attr_rw(sampling_rate);
@@ -459,6 +513,8 @@ cpufreq_freq_attr_rw(up_threshold);
cpufreq_freq_attr_rw(sampling_down_factor);
cpufreq_freq_attr_rw(ignore_nice);
cpufreq_freq_attr_rw(powersave_bias);
+cpufreq_freq_attr_rw(grad_up_threshold);
+cpufreq_freq_attr_rw(early_demand);
cpufreq_freq_attr_ro(sampling_rate_min);

static struct attribute *dbs_attributes[] = {
@@ -469,6 +525,8 @@ static struct attribute *dbs_attributes[] = {
&ignore_nice.attr,
&powersave_bias.attr,
&io_is_busy.attr,
+ &grad_up_threshold.attr,
+ &early_demand.attr,
NULL
};

@@ -516,9 +574,11 @@ static int od_init(struct dbs_data *dbs_data)
}

tuners->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
+ tuners->grad_up_threshold = DEF_GRAD_UP_THRESHOLD;
tuners->ignore_nice = 0;
tuners->powersave_bias = 0;
tuners->io_is_busy = should_io_be_busy();
+ tuners->early_demand = 0;

dbs_data->tuners = tuners;
mutex_init(&dbs_data->mutex);
--
1.8.1.2


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