psi: Add PSI_CPU_FULL state

The FULL state doesn't exist for the CPU resource at the system level,
but exist at the cgroup level, means all non-idle tasks in a cgroup are
delayed on the CPU resource which used by others outside of the cgroup
or throttled by the cgroup cpu.max configuration.
Co-developed-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lkml.kernel.org/r/20210303034659.91735-2-zhouchengming@bytedance.com

include/linux/psi_types.h

@@ -50,9 +50,10 @@ enum psi_states {
 	PSI_MEM_SOME,
 	PSI_MEM_FULL,
 	PSI_CPU_SOME,
+	PSI_CPU_FULL,
 	/* Only per-CPU, to weigh the CPU in the global average: */
 	PSI_NONIDLE,
-	NR_PSI_STATES = 6,
+	NR_PSI_STATES = 7,
 };
 
 enum psi_aggregators {

kernel/sched/psi.c

@@ -34,7 +34,10 @@
  * delayed on that resource such that nobody is advancing and the CPU
  * goes idle. This leaves both workload and CPU unproductive.
  *
- * (Naturally, the FULL state doesn't exist for the CPU resource.)
+ * Naturally, the FULL state doesn't exist for the CPU resource at the
+ * system level, but exist at the cgroup level, means all non-idle tasks
+ * in a cgroup are delayed on the CPU resource which used by others outside
+ * of the cgroup or throttled by the cgroup cpu.max configuration.
  *
  *	SOME = nr_delayed_tasks != 0
  *	FULL = nr_delayed_tasks != 0 && nr_running_tasks == 0
@@ -225,6 +228,8 @@ static bool test_state(unsigned int *tasks, enum psi_states state)
 		return tasks[NR_MEMSTALL] && !tasks[NR_RUNNING];
 	case PSI_CPU_SOME:
 		return tasks[NR_RUNNING] > tasks[NR_ONCPU];
+	case PSI_CPU_FULL:
+		return tasks[NR_RUNNING] && !tasks[NR_ONCPU];
 	case PSI_NONIDLE:
 		return tasks[NR_IOWAIT] || tasks[NR_MEMSTALL] ||
 			tasks[NR_RUNNING];
@@ -678,8 +683,11 @@ static void record_times(struct psi_group_cpu *groupc, int cpu,
 		}
 	}
 
-	if (groupc->state_mask & (1 << PSI_CPU_SOME))
+	if (groupc->state_mask & (1 << PSI_CPU_SOME)) {
 		groupc->times[PSI_CPU_SOME] += delta;
+		if (groupc->state_mask & (1 << PSI_CPU_FULL))
+			groupc->times[PSI_CPU_FULL] += delta;
+	}
 
 	if (groupc->state_mask & (1 << PSI_NONIDLE))
 		groupc->times[PSI_NONIDLE] += delta;
@@ -1018,7 +1026,7 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res)
 		group->avg_next_update = update_averages(group, now);
 	mutex_unlock(&group->avgs_lock);
 
-	for (full = 0; full < 2 - (res == PSI_CPU); full++) {
+	for (full = 0; full < 2; full++) {
 		unsigned long avg[3];
 		u64 total;
 		int w;