Documentation/accounting/psi.rst

4 PSI - Pressure Stall Information
14 either play it safe and under-utilize their hardware resources, or
23 scarcity aids users in sizing workloads to hardware--or provisioning
38 respective file in /proc/pressure/ -- cpu, memory, and io.
52 The "full" line indicates the share of time in which all non-idle
71 Users can register triggers and use poll() to be woken up when resource
75 time window, e.g. 100ms of total stall time within any 500ms window to
81 used to wait for trigger events using select(), poll() or epoll().
87 would add 150ms threshold for partial memory stall measured within
89 would add 50ms threshold for full io stall measured within 1sec time window.
93 file descriptor is required to be able to poll it separately from others,
100 in the stall state psi signal growth is monitored at a rate of 10 times per
103 The kernel accepts window sizes ranging from 500ms to 10s, therefore min
104 monitoring update interval is 50ms and max is 1s. Min limit is set to
113 Notifications to the userspace are rate-limited to one per tracking window.
115 The trigger will de-register when the file descriptor used to define the
126   #include <poll.h>
132    * and 150ms threshold.
155 		n = poll(&fds, 1, -1);
157 			printf("poll error: %s\n", strerror(errno));
184 Per-cgroup psi monitors can be specified and used the same way as
185 system-wide ones.