[CPUFREQ][6/6] cpufreq: Add idle microaccounting in ondemand governor
venkatesh.pallipadi@intel.com [Mon, 4 Aug 2008 18:59:12 +0000 (11:59 -0700)]
Use get_cpu_idle_time_us() to get micro-accounted idle information.
This enables ondemand to get more accurate idle and busy timings
than the jiffy based calculation. As a result, we can decrease
the ondemand safety gaurd band from 80-10 to 95-3.

Results in more aggressive power savings.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>

drivers/cpufreq/cpufreq_ondemand.c

index 3f89860..39253d6 100644 (file)
@@ -18,6 +18,9 @@
 #include <linux/jiffies.h>
 #include <linux/kernel_stat.h>
 #include <linux/mutex.h>
+#include <linux/hrtimer.h>
+#include <linux/tick.h>
+#include <linux/ktime.h>
 
 /*
  * dbs is used in this file as a shortform for demandbased switching
@@ -26,6 +29,8 @@
 
 #define DEF_FREQUENCY_DOWN_DIFFERENTIAL                (10)
 #define DEF_FREQUENCY_UP_THRESHOLD             (80)
+#define MICRO_FREQUENCY_DOWN_DIFFERENTIAL      (3)
+#define MICRO_FREQUENCY_UP_THRESHOLD           (95)
 #define MIN_FREQUENCY_UP_THRESHOLD             (11)
 #define MAX_FREQUENCY_UP_THRESHOLD             (100)
 
@@ -58,6 +63,7 @@ enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};
 struct cpu_dbs_info_s {
        cputime64_t prev_cpu_idle;
        cputime64_t prev_cpu_wall;
+       cputime64_t prev_cpu_nice;
        struct cpufreq_policy *cur_policy;
        struct delayed_work work;
        struct cpufreq_frequency_table *freq_table;
@@ -97,7 +103,8 @@ static struct dbs_tuners {
        .powersave_bias = 0,
 };
 
-static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
+static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu,
+                                                       cputime64_t *wall)
 {
        cputime64_t idle_time;
        cputime64_t cur_wall_time;
@@ -123,6 +130,33 @@ static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
        return idle_time;
 }
 
+static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
+{
+       u64 idle_time = get_cpu_idle_time_us(cpu, wall);
+
+       if (idle_time == -1ULL)
+               return get_cpu_idle_time_jiffy(cpu, wall);
+
+       if (dbs_tuners_ins.ignore_nice) {
+               cputime64_t cur_nice;
+               unsigned long cur_nice_jiffies;
+               struct cpu_dbs_info_s *dbs_info;
+
+               dbs_info = &per_cpu(cpu_dbs_info, cpu);
+               cur_nice = cputime64_sub(kstat_cpu(cpu).cpustat.nice,
+                                        dbs_info->prev_cpu_nice);
+               /*
+                * Assumption: nice time between sampling periods will be
+                * less than 2^32 jiffies for 32 bit sys
+                */
+               cur_nice_jiffies = (unsigned long)
+                                       cputime64_to_jiffies64(cur_nice);
+               dbs_info->prev_cpu_nice = kstat_cpu(cpu).cpustat.nice;
+               return idle_time + jiffies_to_usecs(cur_nice_jiffies);
+       }
+       return idle_time;
+}
+
 /*
  * Find right freq to be set now with powersave_bias on.
  * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
@@ -603,6 +637,15 @@ EXPORT_SYMBOL(cpufreq_gov_ondemand);
 static int __init cpufreq_gov_dbs_init(void)
 {
        int err;
+       cputime64_t wall;
+       u64 idle_time = get_cpu_idle_time_us(smp_processor_id(), &wall);
+
+       if (idle_time != -1ULL) {
+               /* Idle micro accounting is supported. Use finer thresholds */
+               dbs_tuners_ins.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
+               dbs_tuners_ins.down_differential =
+                                       MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
+       }
 
        kondemand_wq = create_workqueue("kondemand");
        if (!kondemand_wq) {