linux-kernel - [PATCH] docs/scheduler: fix unit error

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Message-Id: <20220415033618.15655-1-juitse.huang@gmail.com>
Date:   Fri, 15 Apr 2022 11:36:18 +0800
From:   Jui-Tse Huang <juitse.huang@...il.com>
To:     Jonathan Corbet <corbet@....net>,
        Peter Zijlstra <peterz@...radead.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Huaixin Chang <changhuaixin@...ux.alibaba.com>,
        Beata Michalska <beata.michalska@....com>,
        Chun-Hung Tseng <henrybear327@...il.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Jui-Tse Huang <juitse.huang@...il.com>,
        Ching-Chun Huang <jserv@...s.ncku.edu.tw>
Subject: [PATCH] docs/scheduler: fix unit error

The unit mentioned in the documentation of scheduler statistics is
outdated which may mislead the readers.

The unit of statistics that is reported by /proc/schedstat is modified
to nanosecond, and the unit of statistics that is reported by
/proc/PID/schedstat is provided as well to make the context consistent.

The rq_cpu_time and the rq_sched_info.run_delay of a run queue, and the
sched_info.run_delay of a task are all updated based on the clock of the
run queue, while the se.sum_exec_runtime of a task is updated based on
the clock_task of the run queue of the task. Both the clock and
clock_task are relied on the return value of the function sched_clock()
which is in the unit of nanosecond.

Signed-off-by: Jui-Tse Huang <juitse.huang@...il.com>
---
 Documentation/scheduler/sched-stats.rst | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/Documentation/scheduler/sched-stats.rst b/Documentation/scheduler/sched-stats.rst
index dd9b99a025f7..03c062915998 100644
--- a/Documentation/scheduler/sched-stats.rst
+++ b/Documentation/scheduler/sched-stats.rst
@@ -56,9 +56,9 @@ Next two are try_to_wake_up() statistics:
 
 Next three are statistics describing scheduling latency:
 
-     7) sum of all time spent running by tasks on this processor (in jiffies)
+     7) sum of all time spent running by tasks on this processor (in nanoseconds)
      8) sum of all time spent waiting to run by tasks on this processor (in
-        jiffies)
+        nanoseconds)
      9) # of timeslices run on this cpu
 
 
@@ -155,8 +155,8 @@ schedstats also adds a new /proc/<pid>/schedstat file to include some of
 the same information on a per-process level.  There are three fields in
 this file correlating for that process to:
 
-     1) time spent on the cpu
-     2) time spent waiting on a runqueue
+     1) time spent on the cpu (in nanoseconds)
+     2) time spent waiting on a runqueue (in nanoseconds)
      3) # of timeslices run on this cpu
 
 A program could be easily written to make use of these extra fields to
-- 
2.25.1