[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>

2 files changed, 42 insertions, 98 deletions

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 693e540481b4..a2add11e56f1 100644
--- 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 6f178563e336..09204e40d663 100644
--- 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)