[CPUFREQ] Make ondemand sampling per CPU and remove the mutex usage in sampling path.

Make ondemand sampling per CPU and remove the mutex usage in sampling path.

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>

1 files changed, 32 insertions, 40 deletions

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index a2add11e56f1..18b016ea5f48 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -64,6 +64,7 @@ struct cpu_dbs_info_s {
         cputime64_t prev_cpu_idle;
         cputime64_t prev_cpu_wall;
         struct cpufreq_policy *cur_policy;
+        struct work_struct work;
         unsigned int enable;
 };
 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
@@ -81,7 +82,7 @@ static unsigned int dbs_enable;	/* number of CPUs using this policy */
 static DEFINE_MUTEX (dbs_mutex);
 static DECLARE_WORK     (dbs_work, do_dbs_timer, NULL);
 
-static struct workqueue_struct *dbs_workq;
+static struct workqueue_struct  *kondemand_wq;
 
 struct dbs_tuners {
         unsigned int sampling_rate;
@@ -233,17 +234,15 @@ static struct attribute_group dbs_attr_group = {
 
 /************************** sysfs end ************************/
 
-static void dbs_check_cpu(int cpu)
+static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 {
         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;
 
-        this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
         if (!this_dbs_info->enable)
                 return;
 
@@ -314,35 +313,29 @@ static void dbs_check_cpu(int cpu)
 
 static void do_dbs_timer(void *data)
 {
-        int i;
-        lock_cpu_hotplug();
-        mutex_lock(&dbs_mutex);
-        for_each_online_cpu(i)
-                dbs_check_cpu(i);
-        queue_delayed_work(dbs_workq, &dbs_work,
-                           usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
-        mutex_unlock(&dbs_mutex);
-        unlock_cpu_hotplug();
+        unsigned int cpu = smp_processor_id();
+        struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
+
+        dbs_check_cpu(dbs_info);
+        queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work,
+                        usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 }
 
-static inline void dbs_timer_init(void)
+static inline void dbs_timer_init(unsigned int cpu)
 {
-        INIT_WORK(&dbs_work, do_dbs_timer, NULL);
-        if (!dbs_workq)
-                dbs_workq = create_singlethread_workqueue("ondemand");
-        if (!dbs_workq) {
-                printk(KERN_ERR "ondemand: Cannot initialize kernel thread\n");
-                return;
-        }
-        queue_delayed_work(dbs_workq, &dbs_work,
-                           usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
+        struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
+
+        INIT_WORK(&dbs_info->work, do_dbs_timer, 0);
+        queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work,
+                        usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
         return;
 }
 
-static inline void dbs_timer_exit(void)
+static inline void dbs_timer_exit(unsigned int cpu)
 {
-        if (dbs_workq)
-                cancel_rearming_delayed_workqueue(dbs_workq, &dbs_work);
+        struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
+
+        cancel_rearming_delayed_workqueue(kondemand_wq, &dbs_info->work);
 }
 
 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
@@ -370,6 +363,16 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
                         break;
 
                 mutex_lock(&dbs_mutex);
+                dbs_enable++;
+                if (dbs_enable == 1) {
+                        kondemand_wq = create_workqueue("kondemand");
+                        if (!kondemand_wq) {
+                                printk(KERN_ERR "Creation of kondemand failed\n");
+                                dbs_enable--;
+                                mutex_unlock(&dbs_mutex);
+                                return -ENOSPC;
+                        }
+                }
                 for_each_cpu_mask(j, policy->cpus) {
                         struct cpu_dbs_info_s *j_dbs_info;
                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
@@ -380,7 +383,6 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
                 }
                 this_dbs_info->enable = 1;
                 sysfs_create_group(&policy->kobj, &dbs_attr_group);
-                dbs_enable++;
                 /*
                  * Start the timerschedule work, when this governor
                  * is used for first time
@@ -399,23 +401,20 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 
                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
-                        dbs_timer_init();
                 }
+                dbs_timer_init(policy->cpu);
 
                 mutex_unlock(&dbs_mutex);
                 break;
 
         case CPUFREQ_GOV_STOP:
                 mutex_lock(&dbs_mutex);
+                dbs_timer_exit(policy->cpu);
                 this_dbs_info->enable = 0;
                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
                 dbs_enable--;
-                /*
-                 * Stop the timerschedule work, when this governor
-                 * is used for first time
-                 */
                 if (dbs_enable == 0)
-                        dbs_timer_exit();
+                        destroy_workqueue(kondemand_wq);
 
                 mutex_unlock(&dbs_mutex);
 
@@ -452,13 +451,6 @@ static int __init cpufreq_gov_dbs_init(void)
 
 static void __exit cpufreq_gov_dbs_exit(void)
 {
-        /* Make sure that the scheduled work is indeed not running.
-           Assumes the timer has been cancelled first. */
-        if (dbs_workq) {
-                flush_workqueue(dbs_workq);
-                destroy_workqueue(dbs_workq);
-        }
-
         cpufreq_unregister_governor(&cpufreq_gov_dbs);
 }