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authorStratos Karafotis <stratosk@semaphore.gr>2013-06-05 19:01:25 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-10-09 12:18:43 -0700
commitbed5396573366682b2e07d79a08aefde1c5a8f52 (patch)
tree74c2248427b58000d0fe24c4ce6cd2045e3e261c
parent35c239149f6e5794da2285f30bdeb3b4dd4df3b6 (diff)
cpufreq: ondemand: Change the calculation of target frequency
commit dfa5bb622555d9da0df21b50f46ebdeef390041b upstream. The ondemand governor calculates load in terms of frequency and increases it only if load_freq is greater than up_threshold multiplied by the current or average frequency. This appears to produce oscillations of frequency between min and max because, for example, a relatively small load can easily saturate minimum frequency and lead the CPU to the max. Then, it will decrease back to the min due to small load_freq. Change the calculation method of load and target frequency on the basis of the following two observations: - Load computation should not depend on the current or average measured frequency. For example, absolute load of 80% at 100MHz is not necessarily equivalent to 8% at 1000MHz in the next sampling interval. - It should be possible to increase the target frequency to any value present in the frequency table proportional to the absolute load, rather than to the max only, so that: Target frequency = C * load where we take C = policy->cpuinfo.max_freq / 100. Tested on Intel i7-3770 CPU @ 3.40GHz and on Quad core 1500MHz Krait. Phoronix benchmark of Linux Kernel Compilation 3.1 test shows an increase ~1.5% in performance. cpufreq_stats (time_in_state) shows that middle frequencies are used more, with this patch. Highest and lowest frequencies were used less by ~9%. [rjw: We have run multiple other tests on kernels with this change applied and in the vast majority of cases it turns out that the resulting performance improvement also leads to reduced consumption of energy. The change is additionally justified by the overall simplification of the code in question.] Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Mark Brown <broonie@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/cpufreq/cpufreq_governor.c10
-rw-r--r--drivers/cpufreq/cpufreq_governor.h1
-rw-r--r--drivers/cpufreq/cpufreq_ondemand.c39
3 files changed, 8 insertions, 42 deletions
diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index 28a0b32c73b3..27b0e2a295ea 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c
@@ -97,7 +97,7 @@ void dbs_check_cpu(struct dbs_data *dbs_data, int cpu)
policy = cdbs->cur_policy;
- /* Get Absolute Load (in terms of freq for ondemand gov) */
+ /* Get Absolute Load */
for_each_cpu(j, policy->cpus) {
struct cpu_dbs_common_info *j_cdbs;
u64 cur_wall_time, cur_idle_time;
@@ -148,14 +148,6 @@ void dbs_check_cpu(struct dbs_data *dbs_data, int cpu)
load = 100 * (wall_time - idle_time) / wall_time;
- if (dbs_data->cdata->governor == GOV_ONDEMAND) {
- int freq_avg = __cpufreq_driver_getavg(policy, j);
- if (freq_avg <= 0)
- freq_avg = policy->cur;
-
- load *= freq_avg;
- }
-
if (load > max_load)
max_load = load;
}
diff --git a/drivers/cpufreq/cpufreq_governor.h b/drivers/cpufreq/cpufreq_governor.h
index 0d9e6befe1d5..4a9058aeb57e 100644
--- a/drivers/cpufreq/cpufreq_governor.h
+++ b/drivers/cpufreq/cpufreq_governor.h
@@ -169,7 +169,6 @@ struct od_dbs_tuners {
unsigned int sampling_rate;
unsigned int sampling_down_factor;
unsigned int up_threshold;
- unsigned int adj_up_threshold;
unsigned int powersave_bias;
unsigned int io_is_busy;
};
diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index c087347d6688..25438bbf96bb 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -29,11 +29,9 @@
#include "cpufreq_governor.h"
/* On-demand governor macros */
-#define DEF_FREQUENCY_DOWN_DIFFERENTIAL (10)
#define DEF_FREQUENCY_UP_THRESHOLD (80)
#define DEF_SAMPLING_DOWN_FACTOR (1)
#define MAX_SAMPLING_DOWN_FACTOR (100000)
-#define MICRO_FREQUENCY_DOWN_DIFFERENTIAL (3)
#define MICRO_FREQUENCY_UP_THRESHOLD (95)
#define MICRO_FREQUENCY_MIN_SAMPLE_RATE (10000)
#define MIN_FREQUENCY_UP_THRESHOLD (11)
@@ -161,14 +159,10 @@ static void dbs_freq_increase(struct cpufreq_policy *p, unsigned int freq)
/*
* Every sampling_rate, we check, if current idle time is less than 20%
- * (default), then we try to increase frequency. Every sampling_rate, we look
- * for the lowest frequency which can sustain the load while keeping idle time
- * over 30%. If such a frequency exist, we try to decrease to this frequency.
- *
- * Any frequency increase takes it to the maximum frequency. Frequency reduction
- * happens at minimum steps of 5% (default) of current frequency
+ * (default), then we try to increase frequency. Else, we adjust the frequency
+ * proportional to load.
*/
-static void od_check_cpu(int cpu, unsigned int load_freq)
+static void od_check_cpu(int cpu, unsigned int load)
{
struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
struct cpufreq_policy *policy = dbs_info->cdbs.cur_policy;
@@ -178,29 +172,17 @@ static void od_check_cpu(int cpu, unsigned int load_freq)
dbs_info->freq_lo = 0;
/* Check for frequency increase */
- if (load_freq > od_tuners->up_threshold * policy->cur) {
+ if (load > od_tuners->up_threshold) {
/* 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);
return;
- }
-
- /* Check for frequency decrease */
- /* if we cannot reduce the frequency anymore, break out early */
- if (policy->cur == policy->min)
- return;
-
- /*
- * The optimal frequency is the frequency that is the lowest that can
- * support the current CPU usage without triggering the up policy. To be
- * safe, we focus 10 points under the threshold.
- */
- if (load_freq < od_tuners->adj_up_threshold
- * policy->cur) {
+ } else {
+ /* Calculate the next frequency proportional to load */
unsigned int freq_next;
- freq_next = load_freq / od_tuners->adj_up_threshold;
+ freq_next = load * policy->cpuinfo.max_freq / 100;
/* No longer fully busy, reset rate_mult */
dbs_info->rate_mult = 1;
@@ -374,9 +356,6 @@ static ssize_t store_up_threshold(struct dbs_data *dbs_data, const char *buf,
input < MIN_FREQUENCY_UP_THRESHOLD) {
return -EINVAL;
}
- /* Calculate the new adj_up_threshold */
- od_tuners->adj_up_threshold += input;
- od_tuners->adj_up_threshold -= od_tuners->up_threshold;
od_tuners->up_threshold = input;
return count;
@@ -525,8 +504,6 @@ static int od_init(struct dbs_data *dbs_data)
if (idle_time != -1ULL) {
/* Idle micro accounting is supported. Use finer thresholds */
tuners->up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
- tuners->adj_up_threshold = MICRO_FREQUENCY_UP_THRESHOLD -
- MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
/*
* In nohz/micro accounting case we set the minimum frequency
* not depending on HZ, but fixed (very low). The deferred
@@ -535,8 +512,6 @@ static int od_init(struct dbs_data *dbs_data)
dbs_data->min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
} else {
tuners->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;
- tuners->adj_up_threshold = DEF_FREQUENCY_UP_THRESHOLD -
- DEF_FREQUENCY_DOWN_DIFFERENTIAL;
/* For correct statistics, we need 10 ticks for each measure */
dbs_data->min_sampling_rate = MIN_SAMPLING_RATE_RATIO *