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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE chapter SYSTEM "chapter.dtd">
<chapter>
<header>
<copyright>
<year>2002</year><year>2016</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
</legalnotice>
<title>Erlang Top</title>
<prepared></prepared>
<docno></docno>
<date></date>
<rev></rev>
<file>etop_ug.xml</file>
</header>
<section>
<title>Introduction</title>
<p>Erlang Top, <c>etop</c>, is a tool for presenting information
about Erlang processes similar to the information presented by
<c>top</c> in UNIX.
</p>
</section>
<section>
<title>Getting Started</title>
<p>Start Erlang Top in either of the following ways:</p>
<list type="bulleted">
<item>Use script <c>etop</c>.</item>
<item>Use batch file <c>etop.bat</c>, for example,
<c>etop -node tiger@durin</c>.</item>
</list>
</section>
<section>
<title>Output</title>
<p>The output from Erlang Top is as follows:</p>
<code type="none"><![CDATA[
========================================================================================
tiger@durin 13:40:32
Load: cpu 0 Memory: total 1997 binary 33
procs 197 processes 0 code 173
runq 135 atom 1002 ets 95
Pid Name or Initial Func Time Reds Memory MsgQ Current Function
----------------------------------------------------------------------------------------
<127.23.0> code_server 0 59585 78064 0 gen_server:loop/6
<127.21.0> file_server_2 0 36380 44276 0 gen_server:loop/6
<127.2.0> erl_prim_loader 0 27962 3740 0 erl_prim_loader:loop
<127.9.0> kernel_sup 0 6998 4676 0 gen_server:loop/6
<127.17.0> net_kernel 62 6018 3136 0 gen_server:loop/6
<127.0.0> init 0 4156 4352 0 init:loop/1
<127.16.0> auth 0 1765 1264 0 gen_server:loop/6
<127.18.0> inet_tcp_dist:accept 0 660 1416 0 prim_inet:accept0/2
<127.5.0> application_controll 0 569 6756 0 gen_server:loop/6
<127.137.0> net_kernel:do_spawn_ 0 553 5840 0 dbg:do_relay_1/1
========================================================================================
]]></code>
<p>The header includes some system information:
</p>
<taglist>
<tag><c>Load</c></tag>
<item>
<taglist>
<tag><c>cpu</c></tag>
<item><p><c>Runtime/Wallclock</c>, that is, the percentage of time
where the node has been active.</p></item>
<tag><c>procs</c></tag>
<item><p>The number of processes on the node.</p></item>
<tag><c>runq</c></tag>
<item><p>The number of processes that are ready to run.</p></item>
</taglist>
</item>
<tag><c>Memory</c></tag>
<item><p>The memory allocated by the node in kilobytes.</p></item>
</taglist>
<p>For each process the following information is presented:
</p>
<taglist>
<tag><c>Time</c></tag>
<item><p>The runtime for the process, that is, the time that the process
has been scheduled in.</p></item>
<tag><c>Reds</c></tag>
<item><p>The number of reductions executed on the process.</p></item>
<tag><c>Memory</c></tag>
<item><p>The size of the process in bytes, obtained by a
call to <c>process_info(Pid,memory)</c>.</p></item>
<tag><c>MsgQ</c></tag>
<item><p>The length of the message queue for the process.</p></item>
</taglist>
<note>
<p><em>Time</em> and <em>Reds</em> can be presented as
accumulated values or as values since the last update.</p>
</note>
</section>
<section>
<title>Configuration</title>
<p>All configuration parameters can be set at start by adding
<c>-OptName Value</c> to the command line, for example:</p>
<pre>
% <input>etop -node tiger@durin -setcookie mycookie -lines 15</input></pre>
<p>A list of all valid Erlang Top configuration parameters is available in
module <seealso marker="etop"><c>etop</c></seealso>.
</p>
<p>The parameters <c>lines</c>, <c>interval</c>, <c>accumulate</c>,
and <c>sort</c> can be changed during runtime with function
<seealso marker="etop#config/2"><c>etop:config/2</c></seealso>.
</p>
<p><em>Example:</em></p>
<p>Change configuration parameter <c>lines</c> with text-based presentation.
Before the change, 10 lines are presented as follows:</p>
<code type="none"><![CDATA[
========================================================================================
tiger@durin 10:12:39
Load: cpu 0 Memory: total 1858 binary 33
procs 191 processes 0 code 173
runq 2 atom 1002 ets 95
Pid Name or Initial Func Time Reds Memory MsgQ Current Function
----------------------------------------------------------------------------------------
<127.23.0> code_server 0 60350 71176 0 gen_server:loop/6
<127.21.0> file_server_2 0 36380 44276 0 gen_server:loop/6
<127.2.0> erl_prim_loader 0 27962 3740 0 erl_prim_loader:loop
<127.17.0> net_kernel 0 13808 3916 0 gen_server:loop/6
<127.9.0> kernel_sup 0 6998 4676 0 gen_server:loop/6
<127.0.0> init 0 4156 4352 0 init:loop/1
<127.18.0> inet_tcp_dist:accept 0 2196 1416 0 prim_inet:accept0/2
<127.16.0> auth 0 1893 1264 0 gen_server:loop/6
<127.43.0> ddll_server 0 582 3744 0 gen_server:loop/6
<127.5.0> application_controll 0 569 6756 0 gen_server:loop/6
======================================================================================== ]]></code>
<p>Function <c>etop:config/2</c> is called to change the number of showed
lines to 5:</p>
<pre>
> <input>etop:config(lines,5).</input>
ok</pre>
<p>After the change, 5 lines are presented as follows:</p>
<code type="none"><![CDATA[
(etop@durin)2>
========================================================================================
tiger@durin 10:12:44
Load: cpu 0 Memory: total 1859 binary 33
procs 192 processes 0 code 173
runq 2 atom 1002 ets 95
Pid Name or Initial Func Time Reds Memory MsgQ Current Function
----------------------------------------------------------------------------------------
<127.17.0> net_kernel 183 70 4092 0 gen_server:loop/6
<127.335.0> inet_tcp_dist:do_acc 141 22 1856 0 dist_util:con_loop/9
<127.19.0> net_kernel:ticker/2 155 6 1244 0 net_kernel:ticker1/2
<127.341.0> net_kernel:do_spawn_ 0 0 5840 0 dbg:do_relay_1/1
<127.43.0> ddll_server 0 0 3744 0 gen_server:loop/6
========================================================================================
]]></code>
</section>
<section>
<title>Print to File</title>
<p>At any time, the current Erlang Top display can be dumped to a
text file with function
<seealso marker="etop#dump/1"><c>etop:dump/1</c></seealso>.
</p>
</section>
<section>
<title>Stop</title>
<p>To stop Erlang Top, use function
<seealso marker="etop#stop/0"><c>etop:stop/0</c></seealso>.
</p>
</section>
</chapter>
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