diff options
Diffstat (limited to 'erts/doc')
| -rw-r--r-- | erts/doc/src/erlang.xml | 116 |
1 files changed, 90 insertions, 26 deletions
diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml index 4672c91a8f..30e3b02a0a 100644 --- a/erts/doc/src/erlang.xml +++ b/erts/doc/src/erlang.xml @@ -4352,11 +4352,12 @@ true</pre> <name name="statistics" arity="1" clause_i="2"/> <fsummary>Information about exact reductions</fsummary> <desc> - <p><marker id="statistics_exact_reductions"></marker> - <em>NOTE:</em> <c>statistics(exact_reductions)</c> is - a more expensive operation than - <seealso marker="#statistics_reductions">statistics(reductions)</seealso> - especially on an Erlang machine with SMP support.</p> + <marker id="statistics_exact_reductions"></marker> + <note><p><c>statistics(exact_reductions)</c> is + a more expensive operation than + <seealso marker="#statistics_reductions">statistics(reductions)</seealso> + especially on an Erlang machine with SMP support.</p> + </note> </desc> </func> <func> @@ -4364,6 +4365,10 @@ true</pre> <fsummary>Information about garbage collection</fsummary> <desc> <p>This information may not be valid for all implementations.</p> + <pre> +> <input>statistics(garbage_collection).</input> +{85,23961,0} +</pre> </desc> </func> <func> @@ -4379,12 +4384,18 @@ true</pre> <name name="statistics" arity="1" clause_i="5"/> <fsummary>Information about reductions</fsummary> <desc> - <p><marker id="statistics_reductions"></marker> - <em>NOTE:</em> From erts version 5.5 (OTP release R11B) - this value does not include reductions performed in current - time slices of currently scheduled processes. If an - exact value is wanted, use - <seealso marker="#statistics_exact_reductions">statistics(exact_reductions)</seealso>.</p> + <marker id="statistics_reductions"></marker> + <note> + <p>Since erts-5.5 (OTP release R11B) + this value does not include reductions performed in current + time slices of currently scheduled processes. If an + exact value is wanted, use + <seealso marker="#statistics_exact_reductions">statistics(exact_reductions)</seealso>.</p> + </note> + <pre> +> <input>statistics(reductions).</input> +{2046,11} +</pre> </desc> </func> <func> @@ -4402,25 +4413,78 @@ true</pre> <p>Note that the run-time is the sum of the run-time for all threads in the Erlang run-time system and may therefore be greater than the wall-clock time.</p> + <pre> +> <input>statistics(runtime).</input> +{1690,1620} +</pre> </desc> </func> <func> <name name="statistics" arity="1" clause_i="8"/> <fsummary>Information about each schedulers work time</fsummary> <desc> - <p><marker id="statistics_scheduler_wall_time"></marker> - Returns time lapsed (<c><anno>Scheduler_Total_Time</anno></c>) and time spent working - (<c><anno>Scheduler_Worked_Time</anno></c>) for each scheduler since - the system flag <seealso marker="#system_flag_scheduler_wall_time"><c>scheduler_wall_time</c></seealso> - was set to <c>true</c>.</p> - <p> - Returns <c>undefined</c> if the system flag <seealso marker="#system_flag_scheduler_wall_time"> - <c>scheduler_wall_time</c></seealso> is set to <c>false</c>. - </p> - <p>The list of scheduler information is unsorted and may come in different order - between calls. The time unit is undefined and may be changed and should only be used - to calculate relative utilization. - </p> + <marker id="statistics_scheduler_wall_time"></marker> + <p> + Returns a list of tuples with <c>{<anno>SchedulerId</anno>, + <anno>ActiveTime</anno>, <anno>TotalTime</anno>}</c>, where + <c>SchedulerId</c> is an integer id of the scheduler, <c>ActiveTime</c> is + the duration the scheduler has been busy, <c>TotalTime</c> is the total time duration since + <seealso marker="#system_flag_scheduler_wall_time">scheduler_wall_time</seealso> + activation. The time unit is not defined and may be subject to change + between releases, operating systems and system restarts. + <c>scheduler_wall_time</c> should only be used to calculate relative + values for scheduler-utilization. <c>ActiveTime</c> can never exceed <c>TotalTime</c>. + </p> + + <p>The definition of a busy scheduler is when it is not idle or not + scheduling (selecting) a process or port, meaning; executing process + code, executing linked-in-driver or NIF code, executing + built-in-functions or any other runtime handling, garbage collecting + or handling any other memory management. Note, a scheduler may also be + busy even if the operating system has scheduled out the scheduler + thread. + </p> + + <p> + Returns <c>undefined</c> if the system flag + <seealso marker="#system_flag_scheduler_wall_time">scheduler_wall_time</seealso> + is turned off. + </p> + + <p>The list of scheduler information is unsorted and may appear in different order + between calls. + </p> + <p>Using <c>scheduler_wall_time</c> to calculate scheduler utilization.</p> +<pre> +> <input>erlang:system_flag(scheduler_wall_time, true).</input> +false +> <input>Ts0 = lists:sort(erlang:statistics(scheduler_wall_time)), ok.</input> +ok +</pre> + <p>Some time later we will take another snapshot and calculate scheduler-utilization per scheduler.</p> +<pre> +> <input>Ts1 = lists:sort(erlang:statistics(scheduler_wall_time)), ok.</input> +ok +> <input>lists:map(fun({{I, A0, T0}, {I, A1, T1}}) -> + {I, (A1 - A0)/(T1 - T0)} end, lists:zip(Ts0,Ts1)).</input> +[{1,0.9743474730177548}, + {2,0.9744843782751444}, + {3,0.9995902361669045}, + {4,0.9738012596572161}, + {5,0.9717956667018103}, + {6,0.9739235846420741}, + {7,0.973237033077876}, + {8,0.9741297293248656}] +</pre> + <p>Using the same snapshots to calculate a total scheduler-utilization.</p> +<pre> +> <input>{A, T} = lists:foldl(fun({{_, A0, T0}, {_, A1, T1}}, {Ai,Ti}) -> + {Ai + (A1 - A0), Ti + (T1 - T0)} end, {0, 0}, lists:zip(Ts0,Ts1)), A/T.</input> +0.9769136803764825 +</pre> + <note> + <p><c>scheduler_wall_time</c> is by default disabled. Use <c>erlang:system_flag(scheduler_wall_time, true)</c> to enable it. </p> + </note> </desc> </func> <func> @@ -4445,8 +4509,8 @@ true</pre> <p>A process can be suspended by multiple processes and can be suspended multiple times by a single process. A suspended process will not leave the suspended state until its suspend - count reach zero. The suspend count of <c><anno>Suspendee</anno></c> is - decreased when + count reach zero. The suspend count of <c><anno>Suspendee</anno></c> + is decreased when <seealso marker="#resume_process/1">erlang:resume_process(<anno>Suspendee</anno>)</seealso> is called by the same process that called <c>erlang:suspend_process(<anno>Suspendee</anno>)</c>. All increased suspend |