aboutsummaryrefslogtreecommitdiffstats
path: root/Documentation/accounting/psi.rst
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--Documentation/accounting/psi.rst14
1 files changed, 8 insertions, 6 deletions
diff --git a/Documentation/accounting/psi.rst b/Documentation/accounting/psi.rst
index 621111ce5740..5e40b3f437f9 100644
--- a/Documentation/accounting/psi.rst
+++ b/Documentation/accounting/psi.rst
@@ -1,3 +1,5 @@
+.. _psi:
+
================================
PSI - Pressure Stall Information
================================
@@ -35,11 +37,7 @@ Pressure interface
Pressure information for each resource is exported through the
respective file in /proc/pressure/ -- cpu, memory, and io.
-The format for CPU is as such::
-
- some avg10=0.00 avg60=0.00 avg300=0.00 total=0
-
-and for memory and IO::
+The format is as such::
some avg10=0.00 avg60=0.00 avg300=0.00 total=0
full avg10=0.00 avg60=0.00 avg300=0.00 total=0
@@ -56,6 +54,9 @@ situation from a state where some tasks are stalled but the CPU is
still doing productive work. As such, time spent in this subset of the
stall state is tracked separately and exported in the "full" averages.
+CPU full is undefined at the system level, but has been reported
+since 5.13, so it is set to zero for backward compatibility.
+
The ratios (in %) are tracked as recent trends over ten, sixty, and
three hundred second windows, which gives insight into short term events
as well as medium and long term trends. The total absolute stall time
@@ -90,7 +91,8 @@ Triggers can be set on more than one psi metric and more than one trigger
for the same psi metric can be specified. However for each trigger a separate
file descriptor is required to be able to poll it separately from others,
therefore for each trigger a separate open() syscall should be made even
-when opening the same psi interface file.
+when opening the same psi interface file. Write operations to a file descriptor
+with an already existing psi trigger will fail with EBUSY.
Monitors activate only when system enters stall state for the monitored
psi metric and deactivates upon exit from the stall state. While system is