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authorStratos Karafotis <stratosk@semaphore.gr>2016-11-16 20:26:29 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-11-17 01:15:56 +0300
commit00bfe05889e91b5112893b001e4a47b0a0f8bdd7 (patch)
treeb847ae15c976553f630761b18588232fa26285b1 /drivers/cpufreq/cpufreq_governor.c
parentd5f905a93c321929ad8609c2478c1a5cd00aefdf (diff)
downloadlinux-00bfe05889e91b5112893b001e4a47b0a0f8bdd7.tar.xz
cpufreq: conservative: Decrease frequency faster for deferred updates
Conservative governor changes the CPU frequency in steps. That means that if a CPU runs at max frequency, it will need several sampling periods to return to min frequency when the workload is finished. If the update function that calculates the load and target frequency is deferred, the governor might need even more time to decrease the frequency. This may have impact to power consumption and after all conservative should decrease the frequency if there is no workload at every sampling rate. To resolve the above issue calculate the number of sampling periods that the update is deferred. Considering that for each sampling period conservative should drop the frequency by a freq_step because the CPU was idle apply the proper subtraction to requested frequency. Below, the kernel trace with and without this patch. First an intensive workload is applied on a specific CPU. Then the workload is removed and the CPU goes to idle. WITHOUT <idle>-0 [007] dN.. 620.329153: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-556 [007] .... 620.350857: cpu_frequency: state=1700000 cpu_id=7 kworker/7:2-556 [007] .... 620.370856: cpu_frequency: state=1900000 cpu_id=7 kworker/7:2-556 [007] .... 620.390854: cpu_frequency: state=2100000 cpu_id=7 kworker/7:2-556 [007] .... 620.411853: cpu_frequency: state=2200000 cpu_id=7 kworker/7:2-556 [007] .... 620.432854: cpu_frequency: state=2400000 cpu_id=7 kworker/7:2-556 [007] .... 620.453854: cpu_frequency: state=2600000 cpu_id=7 kworker/7:2-556 [007] .... 620.494856: cpu_frequency: state=2900000 cpu_id=7 kworker/7:2-556 [007] .... 620.515856: cpu_frequency: state=3100000 cpu_id=7 kworker/7:2-556 [007] .... 620.536858: cpu_frequency: state=3300000 cpu_id=7 kworker/7:2-556 [007] .... 620.557857: cpu_frequency: state=3401000 cpu_id=7 <idle>-0 [007] d... 669.591363: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 669.591939: cpu_idle: state=4294967295 cpu_id=7 <idle>-0 [007] d... 669.591980: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] dN.. 669.591989: cpu_idle: state=4294967295 cpu_id=7 ... <idle>-0 [007] d... 670.201224: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 670.221975: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-556 [007] .... 670.222016: cpu_frequency: state=3300000 cpu_id=7 <idle>-0 [007] d... 670.222026: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 670.234964: cpu_idle: state=4294967295 cpu_id=7 ... <idle>-0 [007] d... 670.801251: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 671.236046: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-556 [007] .... 671.236073: cpu_frequency: state=3100000 cpu_id=7 <idle>-0 [007] d... 671.236112: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 671.393437: cpu_idle: state=4294967295 cpu_id=7 ... <idle>-0 [007] d... 671.401277: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 671.404083: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-556 [007] .... 671.404111: cpu_frequency: state=2900000 cpu_id=7 <idle>-0 [007] d... 671.404125: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 671.404974: cpu_idle: state=4294967295 cpu_id=7 ... <idle>-0 [007] d... 671.501180: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 671.995414: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-556 [007] .... 671.995459: cpu_frequency: state=2800000 cpu_id=7 <idle>-0 [007] d... 671.995469: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 671.996287: cpu_idle: state=4294967295 cpu_id=7 ... <idle>-0 [007] d... 672.001305: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 672.078374: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-556 [007] .... 672.078410: cpu_frequency: state=2600000 cpu_id=7 <idle>-0 [007] d... 672.078419: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 672.158020: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-556 [007] .... 672.158040: cpu_frequency: state=2400000 cpu_id=7 <idle>-0 [007] d... 672.158044: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 672.160038: cpu_idle: state=4294967295 cpu_id=7 ... <idle>-0 [007] d... 672.234557: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 672.237121: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-556 [007] .... 672.237174: cpu_frequency: state=2100000 cpu_id=7 <idle>-0 [007] d... 672.237186: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 672.237778: cpu_idle: state=4294967295 cpu_id=7 ... <idle>-0 [007] d... 672.267902: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 672.269860: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-556 [007] .... 672.269906: cpu_frequency: state=1900000 cpu_id=7 <idle>-0 [007] d... 672.269914: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 672.271902: cpu_idle: state=4294967295 cpu_id=7 ... <idle>-0 [007] d... 672.751342: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 672.823056: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-556 [007] .... 672.823095: cpu_frequency: state=1600000 cpu_id=7 WITH <idle>-0 [007] dN.. 4380.928009: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-399 [007] .... 4380.949767: cpu_frequency: state=2000000 cpu_id=7 kworker/7:2-399 [007] .... 4380.969765: cpu_frequency: state=2200000 cpu_id=7 kworker/7:2-399 [007] .... 4381.009766: cpu_frequency: state=2500000 cpu_id=7 kworker/7:2-399 [007] .... 4381.029767: cpu_frequency: state=2600000 cpu_id=7 kworker/7:2-399 [007] .... 4381.049769: cpu_frequency: state=2800000 cpu_id=7 kworker/7:2-399 [007] .... 4381.069769: cpu_frequency: state=3000000 cpu_id=7 kworker/7:2-399 [007] .... 4381.089771: cpu_frequency: state=3100000 cpu_id=7 kworker/7:2-399 [007] .... 4381.109772: cpu_frequency: state=3400000 cpu_id=7 kworker/7:2-399 [007] .... 4381.129773: cpu_frequency: state=3401000 cpu_id=7 <idle>-0 [007] d... 4428.226159: cpu_idle: state=1 cpu_id=7 <idle>-0 [007] d... 4428.226176: cpu_idle: state=4294967295 cpu_id=7 <idle>-0 [007] d... 4428.226181: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 4428.227177: cpu_idle: state=4294967295 cpu_id=7 ... <idle>-0 [007] d... 4428.551640: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 4428.649239: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-399 [007] .... 4428.649268: cpu_frequency: state=2800000 cpu_id=7 <idle>-0 [007] d... 4428.649278: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 4428.689856: cpu_idle: state=4294967295 cpu_id=7 ... <idle>-0 [007] d... 4428.799542: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 4428.801683: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-399 [007] .... 4428.801748: cpu_frequency: state=1700000 cpu_id=7 <idle>-0 [007] d... 4428.801761: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 4428.806545: cpu_idle: state=4294967295 cpu_id=7 ... <idle>-0 [007] d... 4429.051880: cpu_idle: state=4 cpu_id=7 <idle>-0 [007] d... 4429.086240: cpu_idle: state=4294967295 cpu_id=7 kworker/7:2-399 [007] .... 4429.086293: cpu_frequency: state=1600000 cpu_id=7 Without the patch the CPU dropped to min frequency after 3.2s With the patch applied the CPU dropped to min frequency after 0.86s 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>
Diffstat (limited to 'drivers/cpufreq/cpufreq_governor.c')
-rw-r--r--drivers/cpufreq/cpufreq_governor.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index 372947416b75..0196467280bd 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c
@@ -117,7 +117,7 @@ unsigned int dbs_update(struct cpufreq_policy *policy)
struct policy_dbs_info *policy_dbs = policy->governor_data;
struct dbs_data *dbs_data = policy_dbs->dbs_data;
unsigned int ignore_nice = dbs_data->ignore_nice_load;
- unsigned int max_load = 0;
+ unsigned int max_load = 0, idle_periods = UINT_MAX;
unsigned int sampling_rate, io_busy, j;
/*
@@ -215,9 +215,19 @@ unsigned int dbs_update(struct cpufreq_policy *policy)
j_cdbs->prev_load = load;
}
+ if (time_elapsed > 2 * sampling_rate) {
+ unsigned int periods = time_elapsed / sampling_rate;
+
+ if (periods < idle_periods)
+ idle_periods = periods;
+ }
+
if (load > max_load)
max_load = load;
}
+
+ policy_dbs->idle_periods = idle_periods;
+
return max_load;
}
EXPORT_SYMBOL_GPL(dbs_update);