cpufreq: stats: New sysfs attribute for clearing statistics

Allow CPUfreq statistics to be cleared by writing anything to
/sys/.../cpufreq/stats/reset.

Signed-off-by: Markus Mayer <mmayer@broadcom.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/Documentation/cpu-freq/cpufreq-stats.txt b/Documentation/cpu-freq/cpufreq-stats.txt
index 8d9773f..3c355f6 100644 (file)
--- a/Documentation/cpu-freq/cpufreq-stats.txt
+++ b/Documentation/cpu-freq/cpufreq-stats.txt
@@ -44,11 +44,17 @@ the stats driver insertion.
 total 0
 drwxr-xr-x  2 root root    0 May 14 16:06 .
 drwxr-xr-x  3 root root    0 May 14 15:58 ..
+--w-------  1 root root 4096 May 14 16:06 reset
 -r--r--r--  1 root root 4096 May 14 16:06 time_in_state
 -r--r--r--  1 root root 4096 May 14 16:06 total_trans
 -r--r--r--  1 root root 4096 May 14 16:06 trans_table
 --------------------------------------------------------------------------------
 
+-  reset
+Write-only attribute that can be used to reset the stat counters. This can be
+useful for evaluating system behaviour under different governors without the
+need for a reboot.
+
 -  time_in_state
 This gives the amount of time spent in each of the frequencies supported by
 this CPU. The cat output will have "<frequency> <time>" pair in each line, which

diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
index 06d3abd..ac284e6 100644 (file)
--- a/drivers/cpufreq/cpufreq_stats.c
+++ b/drivers/cpufreq/cpufreq_stats.c
@@ -41,6 +41,18 @@ static int cpufreq_stats_update(struct cpufreq_stats *stats)
        return 0;
 }
 
+static void cpufreq_stats_clear_table(struct cpufreq_stats *stats)
+{
+       unsigned int count = stats->max_state;
+
+       memset(stats->time_in_state, 0, count * sizeof(u64));
+#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
+       memset(stats->trans_table, 0, count * count * sizeof(int));
+#endif
+       stats->last_time = get_jiffies_64();
+       stats->total_trans = 0;
+}
+
 static ssize_t show_total_trans(struct cpufreq_policy *policy, char *buf)
 {
        return sprintf(buf, "%d\n", policy->stats->total_trans);
@@ -64,6 +76,14 @@ static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf)
        return len;
 }
 
+static ssize_t store_reset(struct cpufreq_policy *policy, const char *buf,
+                          size_t count)
+{
+       /* We don't care what is written to the attribute. */
+       cpufreq_stats_clear_table(policy->stats);
+       return count;
+}
+
 #ifdef CONFIG_CPU_FREQ_STAT_DETAILS
 static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf)
 {
@@ -113,10 +133,12 @@ cpufreq_freq_attr_ro(trans_table);
 
 cpufreq_freq_attr_ro(total_trans);
 cpufreq_freq_attr_ro(time_in_state);
+cpufreq_freq_attr_wo(reset);
 
 static struct attribute *default_attrs[] = {
        &total_trans.attr,
        &time_in_state.attr,
+       &reset.attr,
 #ifdef CONFIG_CPU_FREQ_STAT_DETAILS
        &trans_table.attr,
 #endif

diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 32dc0cb..40dc2e2 100644 (file)
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -234,6 +234,10 @@ __ATTR(_name, _perm, show_##_name, NULL)
 static struct freq_attr _name =                        \
 __ATTR(_name, 0644, show_##_name, store_##_name)
 
+#define cpufreq_freq_attr_wo(_name)            \
+static struct freq_attr _name =                        \
+__ATTR(_name, 0200, NULL, store_##_name)
+
 struct global_attr {
        struct attribute attr;
        ssize_t (*show)(struct kobject *kobj,