# 4 Erlang Top

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4.1 Introduction

Erlang Top, etop, is a tool for presenting information about Erlang processes similar to the information presented by top in UNIX.

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4.2 Getting Started

Start Erlang Top in either of the following ways:

- Use script etop.
- Use batch file etop.bat, for example, etop -node tiger@durin.

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4.3 Output

The output from Erlang Top is as follows:

    ========================================================================================
     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
    ========================================================================================

The header includes some system information:

Load
  cpu

    Runtime/Wallclock, that is, the percentage of time where the node has been active.

  procs

    The number of processes on the node.

  runq

    The number of processes that are ready to run.

Memory

  The memory allocated by the node in kilobytes.

For each process the following information is presented:

Time

  The runtime for the process, that is, the time that the process has been scheduled in.

Reds

  The number of reductions executed on the process.

Memory

  The size of the process in bytes, obtained by a call to process_info(Pid,memory).

MsgQ

  The length of the message queue for the process.

Note

Time and Reds can be presented as accumulated values or as values since the last update.

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4.4 Configuration

All configuration parameters can be set at start by adding -OptName Value to the command line, for example:

    % etop -node tiger@durin -setcookie mycookie -lines 15

A list of all valid Erlang Top configuration parameters is available in module etop.

The parameters lines, interval, accumulate, and sort can be changed during runtime with function etop:config/2.

Example:

Change configuration parameter lines with text-based presentation. Before the change, 10 lines are presented as follows:

    ========================================================================================
     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
    ========================================================================================

Function etop:config/2 is called to change the number of showed lines to 5:

    > etop:config(lines,5).
    ok

After the change, 5 lines are presented as follows:

    (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
    ========================================================================================

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4.5 Print to File

At any time, the current Erlang Top display can be dumped to a text file with function etop:dump/1.

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4.6 Stop

To stop Erlang Top, use function etop:stop/0.