[PATCH] psi: Clarify the units used in pressure files

[PATCH] psi: Clarify the units used in pressure files

[Waiman Long]

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.

Signed-off-by: Waiman Long <longman@redhat.com>
---
 Documentation/accounting/psi.txt | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/Documentation/accounting/psi.txt b/Documentation/accounting/psi.txt
index b8ca28b60215..7e71c9c1d8e9 100644
--- 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
 =================
-- 
2.18.1

Re: [PATCH] psi: Clarify the units used in pressure files

[Johannes Weiner]

On Tue, Apr 02, 2019 at 03:38:10PM -0400, Waiman Long wrote:
> 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.
> 
> Signed-off-by: Waiman Long <longman@redhat.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

Thanks Waiman!

Re: [PATCH] psi: Clarify the units used in pressure files

[Waiman Long]

On 04/02/2019 05:18 PM, Johannes Weiner wrote:
> On Tue, Apr 02, 2019 at 03:38:10PM -0400, Waiman Long wrote:
>> 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.
>>
>> Signed-off-by: Waiman Long <longman@redhat.com>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
>
> Thanks Waiman!

I had thought about changing the message to show the units somehow, but
that may break existing applications that have dependency on the current
format. So documenting them in psi.txt is the best I can think of.

Cheers,
Longman