10  * When CPU, memory and IO are contended, tasks experience delays that
29  * In the SOME state of a given resource, one or more tasks are
31  * perform work, but the CPU may still be executing other tasks.
33  * In the FULL state of a given resource, all non-idle tasks are
38  * system level, but exist at the cgroup level, means all non-idle tasks
55  * The more tasks and available CPUs there are, the more work can be
58  * tasks and CPUs.
60  * Consider a scenario where 257 number crunching tasks are trying to
68  * Conversely, consider a scenario of 4 tasks and 4 CPUs where at any
69  * given time *one* of the tasks is delayed due to a lack of memory.
76  * we have to base our calculation on the number of non-idle tasks in
79  * delayed tasks to possible threads, and FULL is the share of possible
92  * For the 1 out of 4 memory-delayed tasks, this yields:
226 static bool test_state(unsigned int *tasks, enum psi_states state)  in test_state()  argument
230 		return unlikely(tasks[NR_IOWAIT]);  in test_state()
232 		return unlikely(tasks[NR_IOWAIT] && !tasks[NR_RUNNING]);  in test_state()
234 		return unlikely(tasks[NR_MEMSTALL]);  in test_state()
236 		return unlikely(tasks[NR_MEMSTALL] && !tasks[NR_RUNNING]);  in test_state()
238 		return unlikely(tasks[NR_RUNNING] > tasks[NR_ONCPU]);  in test_state()
240 		return unlikely(tasks[NR_RUNNING] && !tasks[NR_ONCPU]);  in test_state()
242 		return tasks[NR_IOWAIT] || tasks[NR_MEMSTALL] ||  in test_state()
243 			tasks[NR_RUNNING];  in test_state()
697 	 * tasks have been in since the last change, and account any  in psi_group_change()
710 		if (groupc->tasks[t]) {  in psi_group_change()
711 			groupc->tasks[t]--;  in psi_group_change()
713 …	printk_deferred(KERN_ERR "psi: task underflow! cpu=%d t=%d tasks=[%u %u %u %u] clear=%x set=%x\n",  in psi_group_change()
714 					cpu, t, groupc->tasks[0],  in psi_group_change()
715 					groupc->tasks[1], groupc->tasks[2],  in psi_group_change()
716 					groupc->tasks[3], clear, set);  in psi_group_change()
723 			groupc->tasks[t]++;  in psi_group_change()
727 		if (test_state(groupc->tasks, s))  in psi_group_change()
733 	 * when there are no other working tasks, but also when  in psi_group_change()
739 	if (unlikely(groupc->tasks[NR_ONCPU] && cpu_curr(cpu)->in_memstall))  in psi_group_change()
834 		 * When switching between tasks that have an identical  in psi_task_switch()
835 		 * runtime state, the cgroup that contains both tasks  in psi_task_switch()
836 		 * runtime state, the cgroup that contains both tasks  in psi_task_switch()
844 			    per_cpu_ptr(group->pcpu, cpu)->tasks[NR_ONCPU]) {  in psi_task_switch()