</variablelist>
</sect2>
+ <sect2 id="rts-eventlog">
+ <title>Tracing</title>
+
+ <indexterm><primary>tracing</primary></indexterm>
+ <indexterm><primary>events</primary></indexterm>
+ <indexterm><primary>eventlog files</primary></indexterm>
+
+ <para>
+ When the program is linked with the <option>-eventlog</option>
+ option (<xref linkend="options-linker" />), runtime events can
+ be logged in two ways:
+ </para>
+
+ <itemizedlist>
+ <listitem>
+ <para>
+ In binary format to a file for later analysis by a
+ variety of tools. One such tool
+ is <ulink url="http://hackage.haskell.org/package/ThreadScope">ThreadScope</ulink><indexterm><primary>ThreadScope</primary></indexterm>,
+ which interprets the event log to produce a visual parallel
+ execution profile of the program.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ As text to standard output, for debugging purposes.
+ </para>
+ </listitem>
+ </itemizedlist>
+
+ <variablelist>
+ <varlistentry>
+ <term>
+ <option>-l<optional><replaceable>type</replaceable></optional></option>
+ <indexterm><primary><option>-l</option></primary><secondary>RTS option</secondary></indexterm>
+ </term>
+ <listitem>
+ <para>
+ Log events in binary format to the
+ file <filename><replaceable>program</replaceable>.eventlog</filename>,
+ where <replaceable>type</replaceable> indicates the type
+ of events to log. Currently there is only one type
+ supported: <literal>-ls</literal>, for scheduler events.
+ </para>
+
+ <para>
+ The format of the log file is described by the header
+ <filename>EventLogFormat.h</filename> that comes with
+ GHC, and it can be parsed in Haskell using
+ the <ulink url="http://hackage.haskell.org/package/ghc-events">ghc-events</ulink>
+ library. To dump the contents of
+ a <literal>.eventlog</literal> file as text, use the
+ tool <literal>show-ghc-events</literal> that comes with
+ the <ulink url="http://hackage.haskell.org/package/ghc-events">ghc-events</ulink>
+ package.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>
+ <option>-v</option>
+ <indexterm><primary><option>-v</option></primary><secondary>RTS option</secondary></indexterm>
+ </term>
+ <listitem>
+ <para>
+ Log events as text to standard output, instead of to
+ the <literal>.eventlog</literal> file.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ </variablelist>
+
+ <para>
+ The debugging
+ options <option>-D<replaceable>x</replaceable></option> also
+ generate events which are logged using the tracing framework.
+ By default those events are dumped as text to stdout
+ (<option>-D<replaceable>x</replaceable></option>
+ implies <option>-v</option>), but they may instead be stored in
+ the binary eventlog file by using the <option>-l</option>
+ option.
+ </para>
+ </sect2>
+
<sect2 id="rts-options-debugging">
<title>RTS options for hackers, debuggers, and over-interested
souls</title>
<varlistentry>
<term>
- <option>-D</option><replaceable>num</replaceable>
+ <option>-D</option><replaceable>x</replaceable>
<indexterm><primary>-D</primary><secondary>RTS option</secondary></indexterm>
</term>
<listitem>
- <para>An RTS debugging flag; varying quantities of output
- depending on which bits are set in
- <replaceable>num</replaceable>. Only works if the RTS was
- compiled with the <option>DEBUG</option> option.</para>
+ <para>
+ An RTS debugging flag; only availble if the program was
+ linked with the <option>-debug</option> option. Various
+ values of <replaceable>x</replaceable> are provided to
+ enable debug messages and additional runtime sanity checks
+ in different subsystems in the RTS, for
+ example <literal>+RTS -Ds -RTS</literal> enables debug
+ messages from the scheduler.
+ Use <literal>+RTS -?</literal> to find out which
+ debug flags are supported.
+ </para>
+
+ <para>
+ Debug messages will be sent to the binary event log file
+ instead of stdout if the <option>-l</option> option is
+ added. This might be useful for reducing the overhead of
+ debug tracing.
+ </para>
</listitem>
</varlistentry>
</term>
<listitem>
<para>Produce “ticky-ticky” statistics at the
- end of the program run. The <replaceable>file</replaceable>
- business works just like on the <option>-S</option> RTS
- option (above).</para>
-
- <para>“Ticky-ticky” statistics are counts of
- various program actions (updates, enters, etc.) The program
- must have been compiled using
- <option>-ticky</option><indexterm><primary><option>-ticky</option></primary></indexterm>
- (a.k.a. “ticky-ticky profiling”), and, for it to
- be really useful, linked with suitable system libraries.
- Not a trivial undertaking: consult the installation guide on
- how to set things up for easy “ticky-ticky”
- profiling. For more information, see <xref
- linkend="ticky-ticky"/>.</para>
+ end of the program run (only available if the program was
+ linked with <option>-debug</option>).
+ The <replaceable>file</replaceable> business works just like
+ on the <option>-S</option> RTS option, above.</para>
+
+ <para>For more information on ticky-ticky profiling, see
+ <xref linkend="ticky-ticky"/>.</para>
</listitem>
</varlistentry>