Document the change to +RTS -S/-s/-t

[ghc-hetmet.git] / docs / users_guide / runtime_control.xml

diff --git a/docs/users_guide/runtime_control.xml b/docs/users_guide/runtime_control.xml
index 183cd9c..725ee88 100644 (file)
--- a/docs/users_guide/runtime_control.xml
+++ b/docs/users_guide/runtime_control.xml
@@ -436,46 +436,35 @@
       </varlistentry>
 
       <varlistentry>
+        <term>
+          <option>-t</option><optional><replaceable>file</replaceable></optional>
+          <indexterm><primary><option>-t</option></primary><secondary>RTS option</secondary></indexterm>
+        </term>
        <term>
-          <option>-s</option><replaceable>file</replaceable>
+          <option>-s</option><optional><replaceable>file</replaceable></optional>
           <indexterm><primary><option>-s</option></primary><secondary>RTS option</secondary></indexterm>
         </term>
        <term>
-          <option>-S</option><replaceable>file</replaceable>
+          <option>-S</option><optional><replaceable>file</replaceable></optional>
           <indexterm><primary><option>-S</option></primary><secondary>RTS option</secondary></indexterm>
         </term>
        <listitem>
-         <para>Write modest (<option>-s</option>) or verbose
-          (<option>-S</option>) garbage-collector statistics into file
-          <replaceable>file</replaceable>. The default
-          <replaceable>file</replaceable> is
-          <filename><replaceable>program</replaceable>.stat</filename>. The
-          <replaceable>file</replaceable> <constant>stderr</constant>
-          is treated specially, with the output really being sent to
-          <constant>stderr</constant>.</para>
-
-         <para>This option is useful for watching how the storage
-          manager adjusts the heap size based on the current amount of
-          live data.</para>
-       </listitem>
-      </varlistentry>
+         <para>These options produce runtime-system statistics, such
+         as the amount of time spent executing the program and in the
+         garbage collector, the amount of memory allocated, the
+         maximum size of the heap, and so on.  The three
+         variants give different levels of detail:
+         <option>-t</option> produces a single line of output in the
+         same format as GHC's <option>-Rghc-timing</option> option,
+         <option>-s</option> produces a more detailed summary at the
+         end of the program, and <option>-S</option> additionally
+         produces information about each and every garbage
+         collection.</para>
 
-      <varlistentry>
-       <term>
-          <option>-t<replaceable>file</replaceable></option>
-          <indexterm><primary><option>-t</option></primary><secondary>RTS option</secondary></indexterm>
-        </term>
-       <listitem>
-         <para>Write a one-line GC stats summary after running the
-         program.  This output is in the same format as that produced
-         by the <option>-Rghc-timing</option> option.</para>
-
-         <para>As with <option>-s</option>, the default
-          <replaceable>file</replaceable> is
-          <filename><replaceable>program</replaceable>.stat</filename>. The
-          <replaceable>file</replaceable> <constant>stderr</constant>
-          is treated specially, with the output really being sent to
-          <constant>stderr</constant>.</para>
+          <para>The output is placed in
+          <replaceable>file</replaceable>.  If
+          <replaceable>file</replaceable> is omitted, then the output
+          is sent to <constant>stderr</constant>.</para>
        </listitem>
       </varlistentry>
     </variablelist>