[CPUFREQ] Remove slowdown from ondemand sampling path.

Remove slowdown from ondemand sampling path. This reduces the code path length
in dbs_check_cpu() by half. slowdown was not used by ondemand by default.
If there are any user level tools that were using this tunable, they
may report error now.

Signed-off-by: Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 693e540481b4cb88095664c0d2b6f55979d17a10..a2add11e56f1c67941f7270f65135060c5336451 100644 (file)
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -56,16 +56,14 @@ static unsigned int def_sampling_rate;
 #define MIN_SAMPLING_RATE                      (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
 #define MAX_SAMPLING_RATE                      (500 * def_sampling_rate)
 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER   (1000)
-#define DEF_SAMPLING_DOWN_FACTOR               (1)
-#define MAX_SAMPLING_DOWN_FACTOR               (10)
 #define TRANSITION_LATENCY_LIMIT               (10 * 1000)
 
 static void do_dbs_timer(void *data);
 
 struct cpu_dbs_info_s {
+       cputime64_t prev_cpu_idle;
+       cputime64_t prev_cpu_wall;
        struct cpufreq_policy *cur_policy;
-       unsigned int prev_cpu_idle_up;
-       unsigned int prev_cpu_idle_down;
        unsigned int enable;
 };
 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
@@ -87,24 +85,26 @@ static struct workqueue_struct *dbs_workq;
 
 struct dbs_tuners {
        unsigned int sampling_rate;
-       unsigned int sampling_down_factor;
        unsigned int up_threshold;
        unsigned int ignore_nice;
 };
 
 static struct dbs_tuners dbs_tuners_ins = {
        .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
-       .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
        .ignore_nice = 0,
 };
 
-static inline unsigned int get_cpu_idle_time(unsigned int cpu)
+static inline cputime64_t get_cpu_idle_time(unsigned int cpu)
 {
-       return  kstat_cpu(cpu).cpustat.idle +
-               kstat_cpu(cpu).cpustat.iowait +
-               ( dbs_tuners_ins.ignore_nice ?
-                 kstat_cpu(cpu).cpustat.nice :
-                 0);
+       cputime64_t retval;
+
+       retval = cputime64_add(kstat_cpu(cpu).cpustat.idle,
+                       kstat_cpu(cpu).cpustat.iowait);
+
+       if (dbs_tuners_ins.ignore_nice)
+               retval = cputime64_add(retval, kstat_cpu(cpu).cpustat.nice);
+
+       return retval;
 }
 
 /************************** sysfs interface ************************/
@@ -133,29 +133,9 @@ static ssize_t show_##file_name                                            \
        return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 }
 show_one(sampling_rate, sampling_rate);
-show_one(sampling_down_factor, sampling_down_factor);
 show_one(up_threshold, up_threshold);
 show_one(ignore_nice_load, ignore_nice);
 
-static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
-               const char *buf, size_t count)
-{
-       unsigned int input;
-       int ret;
-       ret = sscanf (buf, "%u", &input);
-       if (ret != 1 )
-               return -EINVAL;
-
-       if (input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
-               return -EINVAL;
-
-       mutex_lock(&dbs_mutex);
-       dbs_tuners_ins.sampling_down_factor = input;
-       mutex_unlock(&dbs_mutex);
-
-       return count;
-}
-
 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
                const char *buf, size_t count)
 {
@@ -217,12 +197,12 @@ static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
        }
        dbs_tuners_ins.ignore_nice = input;
 
-       /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
+       /* we need to re-evaluate prev_cpu_idle */
        for_each_online_cpu(j) {
-               struct cpu_dbs_info_s *j_dbs_info;
-               j_dbs_info = &per_cpu(cpu_dbs_info, j);
-               j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
-               j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
+               struct cpu_dbs_info_s *dbs_info;
+               dbs_info = &per_cpu(cpu_dbs_info, j);
+               dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
+               dbs_info->prev_cpu_wall = get_jiffies_64();
        }
        mutex_unlock(&dbs_mutex);
 
@@ -234,7 +214,6 @@ static struct freq_attr _name = \
 __ATTR(_name, 0644, show_##_name, store_##_name)
 
 define_one_rw(sampling_rate);
-define_one_rw(sampling_down_factor);
 define_one_rw(up_threshold);
 define_one_rw(ignore_nice_load);
 
@@ -242,7 +221,6 @@ static struct attribute * dbs_attributes[] = {
        &sampling_rate_max.attr,
        &sampling_rate_min.attr,
        &sampling_rate.attr,
-       &sampling_down_factor.attr,
        &up_threshold.attr,
        &ignore_nice_load.attr,
        NULL
@@ -257,11 +235,10 @@ static struct attribute_group dbs_attr_group = {
 
 static void dbs_check_cpu(int cpu)
 {
-       unsigned int idle_ticks, up_idle_ticks, total_ticks;
-       unsigned int freq_next;
-       unsigned int freq_down_sampling_rate;
-       static int down_skip[NR_CPUS];
+       unsigned int idle_ticks, total_ticks;
+       unsigned int load;
        struct cpu_dbs_info_s *this_dbs_info;
+       cputime64_t cur_jiffies;
 
        struct cpufreq_policy *policy;
        unsigned int j;
@@ -271,10 +248,14 @@ static void dbs_check_cpu(int cpu)
                return;
 
        policy = this_dbs_info->cur_policy;
+       cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());
+       total_ticks = (unsigned int) cputime64_sub(cur_jiffies,
+                       this_dbs_info->prev_cpu_wall);
+       this_dbs_info->prev_cpu_wall = cur_jiffies;
        /*
         * Every sampling_rate, we check, if current idle time is less
         * than 20% (default), then we try to increase frequency
-        * Every sampling_rate*sampling_down_factor, we look for a the lowest
+        * Every sampling_rate, we look for a 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.
         *
@@ -283,36 +264,26 @@ static void dbs_check_cpu(int cpu)
         * 5% (default) of current frequency
         */
 
-       /* Check for frequency increase */
+       /* Get Idle Time */
        idle_ticks = UINT_MAX;
        for_each_cpu_mask(j, policy->cpus) {
-               unsigned int tmp_idle_ticks, total_idle_ticks;
+               cputime64_t total_idle_ticks;
+               unsigned int tmp_idle_ticks;
                struct cpu_dbs_info_s *j_dbs_info;
 
                j_dbs_info = &per_cpu(cpu_dbs_info, j);
                total_idle_ticks = get_cpu_idle_time(j);
-               tmp_idle_ticks = total_idle_ticks -
-                       j_dbs_info->prev_cpu_idle_up;
-               j_dbs_info->prev_cpu_idle_up = total_idle_ticks;
+               tmp_idle_ticks = (unsigned int) cputime64_sub(total_idle_ticks,
+                               j_dbs_info->prev_cpu_idle);
+               j_dbs_info->prev_cpu_idle = total_idle_ticks;
 
                if (tmp_idle_ticks < idle_ticks)
                        idle_ticks = tmp_idle_ticks;
        }
+       load = (100 * (total_ticks - idle_ticks)) / total_ticks;
 
-       /* Scale idle ticks by 100 and compare with up and down ticks */
-       idle_ticks *= 100;
-       up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
-                       usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
-
-       if (idle_ticks < up_idle_ticks) {
-               down_skip[cpu] = 0;
-               for_each_cpu_mask(j, policy->cpus) {
-                       struct cpu_dbs_info_s *j_dbs_info;
-
-                       j_dbs_info = &per_cpu(cpu_dbs_info, j);
-                       j_dbs_info->prev_cpu_idle_down =
-                                       j_dbs_info->prev_cpu_idle_up;
-               }
+       /* Check for frequency increase */
+       if (load > dbs_tuners_ins.up_threshold) {
                /* if we are already at full speed then break out early */
                if (policy->cur == policy->max)
                        return;
@@ -323,50 +294,22 @@ static void dbs_check_cpu(int cpu)
        }
 
        /* Check for frequency decrease */
-       down_skip[cpu]++;
-       if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
-               return;
-
-       idle_ticks = UINT_MAX;
-       for_each_cpu_mask(j, policy->cpus) {
-               unsigned int tmp_idle_ticks, total_idle_ticks;
-               struct cpu_dbs_info_s *j_dbs_info;
-
-               j_dbs_info = &per_cpu(cpu_dbs_info, j);
-               /* Check for frequency decrease */
-               total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
-               tmp_idle_ticks = total_idle_ticks -
-                       j_dbs_info->prev_cpu_idle_down;
-               j_dbs_info->prev_cpu_idle_down = total_idle_ticks;
-
-               if (tmp_idle_ticks < idle_ticks)
-                       idle_ticks = tmp_idle_ticks;
-       }
-
-       down_skip[cpu] = 0;
        /* if we cannot reduce the frequency anymore, break out early */
        if (policy->cur == policy->min)
                return;
 
-       /* Compute how many ticks there are between two measurements */
-       freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
-               dbs_tuners_ins.sampling_down_factor;
-       total_ticks = usecs_to_jiffies(freq_down_sampling_rate);
-
        /*
         * 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.
         */
-       freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;
-       freq_next = (freq_next * policy->cur) /
+       if (load < (dbs_tuners_ins.up_threshold - 10)) {
+               unsigned int freq_next;
+               freq_next = (policy->cur * load) /
                        (dbs_tuners_ins.up_threshold - 10);
 
-       if (freq_next < policy->min)
-               freq_next = policy->min;
-
-       if (freq_next <= ((policy->cur * 95) / 100))
                __cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);
+       }
 }
 
 static void do_dbs_timer(void *data)
@@ -432,9 +375,8 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
                        j_dbs_info = &per_cpu(cpu_dbs_info, j);
                        j_dbs_info->cur_policy = policy;
 
-                       j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
-                       j_dbs_info->prev_cpu_idle_down
-                               = j_dbs_info->prev_cpu_idle_up;
+                       j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
+                       j_dbs_info->prev_cpu_wall = get_jiffies_64();
                }
                this_dbs_info->enable = 1;
                sysfs_create_group(&policy->kobj, &dbs_attr_group);

diff --git a/include/asm-generic/cputime.h b/include/asm-generic/cputime.h
index 6f178563e336c396c1b3b12b314e913c83f7ea76..09204e40d66312edb7ba12e58261fd4760a89939 100644 (file)
--- a/include/asm-generic/cputime.h
+++ b/include/asm-generic/cputime.h
@@ -24,7 +24,9 @@ typedef u64 cputime64_t;
 
 #define cputime64_zero (0ULL)
 #define cputime64_add(__a, __b)                ((__a) + (__b))
+#define cputime64_sub(__a, __b)                ((__a) - (__b))
 #define cputime64_to_jiffies64(__ct)   (__ct)
+#define jiffies64_to_cputime64(__jif)  (__jif)
 #define cputime_to_cputime64(__ct)     ((u64) __ct)