diff options
| author | Sverker Eriksson <sverker@erlang.org> | 2021-11-22 23:08:08 +0100 |
|---|---|---|
| committer | Sverker Eriksson <sverker@erlang.org> | 2022-01-11 22:55:03 +0100 |
| commit | 0e3db5dd1eb310519a5b5cd0d2da4acd1dab8177 (patch) | |
| tree | a5daea89047767edca417dc34677c25c42ac7050 /erts/doc | |
| parent | f2cfea03520d106a46d24d0bbde9ebc631c532c6 (diff) | |
| download | erlang-0e3db5dd1eb310519a5b5cd0d2da4acd1dab8177.tar.gz | |
erts: Clarify system_flag(scheduler_wall_time,_) docs
Diffstat (limited to 'erts/doc')
| -rw-r--r-- | erts/doc/src/erlang.xml | 34 |
1 files changed, 30 insertions, 4 deletions
diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml index 26f3f768f6..39c2095dc8 100644 --- a/erts/doc/src/erlang.xml +++ b/erts/doc/src/erlang.xml @@ -9350,10 +9350,36 @@ ok <fsummary>Set system flag scheduler_wall_time.</fsummary> <desc> <p> - Turns on or off scheduler wall time measurements.</p> - <p>For more information, see - <seeerl marker="#statistics_scheduler_wall_time"> - <c>statistics(scheduler_wall_time)</c></seeerl>.</p> + Try enable or disable scheduler wall time measurements by passing + <c><anno>Boolean</anno></c> as either <c>true</c> or <c>false</c>. + </p> + <p> + For more information about how to use scheduler wall time + measurements, see <seeerl marker="#statistics_scheduler_wall_time"> + <c>statistics(scheduler_wall_time)</c></seeerl>. + </p> + <p> + Scheduler wall time measurements has a node global state. It is either + enabled for all processes on the node or disabled for all + processes. Each process has a logical counter initialized as zero. A + call with <c><anno>Boolean</anno></c> as <c>true</c> will increase + that counter one step for the calling process. A call with + <c>false</c> will decrease it one step unless it already is + zero. The node global state for <c>scheduler_wall_time</c> will be + enabled as long as there is at least one process alive with a counter + value larger than zero. When a process terminates, its counter will + also disappear. To ensure <c>scheduler_wall_time</c> is kept enabled, + the process that enabled it must therefore be kept alive. + </p> + <p> + Returns the old value of the node global state, <c>true</c> if + scheduler wall time measurements were enabled, <c>false</c> + if it were disabled. + </p> + <p> + Scheduler wall time measurements do consume some cpu overhead and + should not be left turned on unless used. + </p> </desc> </func> |