psi: clarify the units used in pressure files

The output of the PSI files show a bunch of numbers with no unit.  The
psi.txt documentation file also does not indicate what units are used.
One can only find out by looking at the source code.  The units are
percentage for the averages and useconds for the total.  Make the
information easier to find by documenting the units in psi.txt.

Link: http://lkml.kernel.org/r/20190402193810.3450-1-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/accounting/psi.txt b/Documentation/accounting/psi.txt
index b8ca28b60215a48f1ee99cfae36f20e0b8d0e8da..7e71c9c1d8e9c7eee70ef957610b483a58739232 100644 (file)
--- a/Documentation/accounting/psi.txt
+++ b/Documentation/accounting/psi.txt
@@ -56,12 +56,12 @@ 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.
 
-The ratios 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 is
-tracked and exported as well, to allow detection of latency spikes
-which wouldn't necessarily make a dent in the time averages, or to
-average trends over custom time frames.
+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
+(in us) is tracked and exported as well, to allow detection of latency
+spikes which wouldn't necessarily make a dent in the time averages,
+or to average trends over custom time frames.
 
 Cgroup2 interface
 =================