sched/cputime: Provide get_cpu_[idle|iowait]_time_us() off-case

The last reason why get_cpu_idle/iowait_time_us() may return -1 now is if
the config doesn't support nohz.

The ad-hoc replacement solution by cpufreq is to compute jiffies minus the
whole busy cputime. Although the intention should provide a coherent low
resolution estimation of the idle and iowait time, the implementation is
buggy because jiffies don't start at 0.

Just provide instead a real get_cpu_[idle|iowait]_time_us() offcase.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Link: https://patch.msgid.link/20260508131647.43868-14-frederic@kernel.org

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 44eb1b7e7fc1bc6d683fdcb135cc532dd2c9e86e..dda0d34d3c02d6f5a83768f688baff76121551fd 100644 (file)
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -130,38 +130,11 @@ struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy)
 }
 EXPORT_SYMBOL_GPL(get_governor_parent_kobj);
 
-static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
-{
-       struct kernel_cpustat kcpustat;
-       u64 cur_wall_time;
-       u64 idle_time;
-       u64 busy_time;
-
-       cur_wall_time = jiffies64_to_nsecs(get_jiffies_64());
-
-       kcpustat_cpu_fetch(&kcpustat, cpu);
-
-       busy_time = kcpustat.cpustat[CPUTIME_USER];
-       busy_time += kcpustat.cpustat[CPUTIME_SYSTEM];
-       busy_time += kcpustat.cpustat[CPUTIME_IRQ];
-       busy_time += kcpustat.cpustat[CPUTIME_SOFTIRQ];
-       busy_time += kcpustat.cpustat[CPUTIME_STEAL];
-       busy_time += kcpustat.cpustat[CPUTIME_NICE];
-
-       idle_time = cur_wall_time - busy_time;
-       if (wall)
-               *wall = div_u64(cur_wall_time, NSEC_PER_USEC);
-
-       return div_u64(idle_time, NSEC_PER_USEC);
-}
-
 u64 get_cpu_idle_time(unsigned int cpu, u64 *wall, int io_busy)
 {
        u64 idle_time = get_cpu_idle_time_us(cpu, io_busy ? wall : NULL);
 
-       if (idle_time == -1ULL)
-               return get_cpu_idle_time_jiffy(cpu, wall);
-       else if (!io_busy)
+       if (!io_busy)
                idle_time += get_cpu_iowait_time_us(cpu, wall);
 
        return idle_time;

diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
index 3680519d7b2c45a763571ff0df13c40e967ca5bd..512104b0ff49ba7d1271a72f7c2f2ade8ea61d7b 100644 (file)
--- a/include/linux/kernel_stat.h
+++ b/include/linux/kernel_stat.h
@@ -133,6 +133,9 @@ static inline bool kcpustat_idle_dyntick(void)
 }
 #endif /* CONFIG_NO_HZ_COMMON */
 
+extern u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time);
+extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time);
+
 /* Fetch cputime values when vtime is disabled on a CPU */
 static inline u64 kcpustat_field_default(enum cpu_usage_stat usage, int cpu)
 {

diff --git a/include/linux/tick.h b/include/linux/tick.h
index 738007d6f577ffca799bdb541dc7016e971956d4..1cf4651f09ad61bc1af73f40b1ad632931f15e6e 100644 (file)
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -139,8 +139,6 @@ extern bool tick_nohz_idle_got_tick(void);
 extern ktime_t tick_nohz_get_next_hrtimer(void);
 extern ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next);
 extern unsigned long tick_nohz_get_idle_calls_cpu(int cpu);
-extern u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time);
-extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time);
 #else /* !CONFIG_NO_HZ_COMMON */
 #define tick_nohz_enabled (0)
 static inline bool tick_nohz_is_active(void) { return false; }
@@ -162,8 +160,6 @@ static inline ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next)
        *delta_next = TICK_NSEC;
        return *delta_next;
 }
-static inline u64 get_cpu_idle_time_us(int cpu, u64 *unused) { return -1; }
-static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; }
 #endif /* !CONFIG_NO_HZ_COMMON */
 
 /*

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index c91fd67f93ea99865bebed96eb585cb9ad683555..335d2c1277633d747206bafccbfd8692cb6980dc 100644 (file)
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -522,6 +522,13 @@ u64 kcpustat_field_iowait(int cpu)
                                      nr_iowait_cpu(cpu), ktime_get());
 }
 EXPORT_SYMBOL_GPL(kcpustat_field_iowait);
+#else
+static u64 kcpustat_field_dyntick(int cpu, enum cpu_usage_stat idx,
+                                 bool compute_delta, ktime_t now)
+{
+       return kcpustat_cpu(cpu).cpustat[idx];
+}
+#endif /* CONFIG_NO_HZ_COMMON */
 
 static u64 get_cpu_sleep_time_us(int cpu, enum cpu_usage_stat idx,
                                 bool compute_delta, u64 *last_update_time)
@@ -557,7 +564,7 @@ static u64 get_cpu_sleep_time_us(int cpu, enum cpu_usage_stat idx,
  * This time is measured via accounting rather than sampling,
  * and is as accurate as ktime_get() is.
  *
- * Return: -1 if generic vtime is enabled, else total idle time of the @cpu
+ * Return: total idle time of the @cpu
  */
 u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
 {
@@ -581,7 +588,7 @@ EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
  * This time is measured via accounting rather than sampling,
  * and is as accurate as ktime_get() is.
  *
- * Return: -1 if generic vtime is enabled, else total iowait time of @cpu
+ * Return: total iowait time of @cpu
  */
 u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
 {
@@ -589,7 +596,6 @@ u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
                                     nr_iowait_cpu(cpu), last_update_time);
 }
 EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
-#endif /* CONFIG_NO_HZ_COMMON */
 
 /*
  * Use precise platform statistics if available: