11  * When CPU, memory and IO are contended, tasks experience delays that
30  * In the SOME state of a given resource, one or more tasks are
32  * perform work, but the CPU may still be executing other tasks.
34  * In the FULL state of a given resource, all non-idle tasks are
48  * FULL means all non-idle tasks in the cgroup are delayed on the CPU
62  * The more tasks and available CPUs there are, the more work can be
65  * tasks and CPUs.
67  * Consider a scenario where 257 number crunching tasks are trying to
75  * Conversely, consider a scenario of 4 tasks and 4 CPUs where at any
76  * given time *one* of the tasks is delayed due to a lack of memory.
83  * we have to base our calculation on the number of non-idle tasks in
86  * delayed tasks to possible threads, and FULL is the share of possible
99  * For the 1 out of 4 memory-delayed tasks, this yields:
216 static bool test_state(unsigned int *tasks, enum psi_states state, bool oncpu)  in test_state()  argument
220 		return unlikely(tasks[NR_IOWAIT]);  in test_state()
222 		return unlikely(tasks[NR_IOWAIT] && !tasks[NR_RUNNING]);  in test_state()
224 		return unlikely(tasks[NR_MEMSTALL]);  in test_state()
226 		return unlikely(tasks[NR_MEMSTALL] &&  in test_state()
227 			tasks[NR_RUNNING] == tasks[NR_MEMSTALL_RUNNING]);  in test_state()
229 		return unlikely(tasks[NR_RUNNING] > oncpu);  in test_state()
231 		return unlikely(tasks[NR_RUNNING] && !oncpu);  in test_state()
233 		return tasks[NR_IOWAIT] || tasks[NR_MEMSTALL] ||  in test_state()
234 			tasks[NR_RUNNING];  in test_state()
704 	 * assess the aggregate resource states this CPU's tasks  in psi_group_change()
733 		if (groupc->tasks[t]) {  in psi_group_change()
734 			groupc->tasks[t]--;  in psi_group_change()
736 …	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()
737 					cpu, t, groupc->tasks[0],  in psi_group_change()
738 					groupc->tasks[1], groupc->tasks[2],  in psi_group_change()
739 					groupc->tasks[3], clear, set);  in psi_group_change()
746 			groupc->tasks[t]++;  in psi_group_change()
766 		if (test_state(groupc->tasks, s, state_mask & PSI_ONCPU))  in psi_group_change()
772 	 * when there are no other working tasks, but also when  in psi_group_change()
902 		 * any other differences between the two tasks (e.g. prev goes  in psi_task_switch()
1114 	 * stop percpu tasks accounting in each psi_group_cpu,  in psi_cgroup_restart()
1123 	 * to get correct state mask from test_state() loop on tasks[],  in psi_cgroup_restart()