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
52  * The more tasks and available CPUs there are, the more work can be
55  * tasks and CPUs.
57  * Consider a scenario where 257 number crunching tasks are trying to
65  * Conversely, consider a scenario of 4 tasks and 4 CPUs where at any
66  * given time *one* of the tasks is delayed due to a lack of memory.
73  * we have to base our calculation on the number of non-idle tasks in
76  * delayed tasks to possibe threads, and FULL is the share of possible
89  * For the 1 out of 4 memory-delayed tasks, this yields:
215 static bool test_state(unsigned int *tasks, enum psi_states state)  in test_state()  argument
219 		return tasks[NR_IOWAIT];  in test_state()
221 		return tasks[NR_IOWAIT] && !tasks[NR_RUNNING];  in test_state()
223 		return tasks[NR_MEMSTALL];  in test_state()
225 		return tasks[NR_MEMSTALL] && !tasks[NR_RUNNING];  in test_state()
227 		return tasks[NR_RUNNING] > tasks[NR_ONCPU];  in test_state()
229 		return tasks[NR_IOWAIT] || tasks[NR_MEMSTALL] ||  in test_state()
230 			tasks[NR_RUNNING];  in test_state()
667 			 * working tasks, but also when the CPU is  in record_times()
672 			 * regardless of runnable tasks, sample a FULL  in record_times()
701 	 * tasks have been in since the last change, and account any  in psi_group_change()
714 		if (groupc->tasks[t] == 0 && !psi_bug) {  in psi_group_change()
715 …	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()
716 					cpu, t, groupc->tasks[0],  in psi_group_change()
717 					groupc->tasks[1], groupc->tasks[2],  in psi_group_change()
718 					groupc->tasks[3], clear, set);  in psi_group_change()
721 		groupc->tasks[t]--;  in psi_group_change()
726 			groupc->tasks[t]++;  in psi_group_change()
730 		if (test_state(groupc->tasks, s))  in psi_group_change()
820 		 * When moving state between tasks, the group that  in psi_task_switch()
828 			if (per_cpu_ptr(group->pcpu, cpu)->tasks[NR_ONCPU]) {  in psi_task_switch()