+
+ <para>The following options affect the way the runtime schedules
+ threads on CPUs:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><option>-qm</option></term>
+ <indexterm><primary><option>-qm</option></primary><secondary>RTS
+ option</secondary></indexterm>
+ <listitem>
+ <para>Disable automatic migration for load balancing.
+ Normally the runtime will automatically try to schedule
+ threads across the available CPUs to make use of idle
+ CPUs; this option disables that behaviour. It is probably
+ only of use if you are explicitly scheduling threads onto
+ CPUs with <literal>GHC.Conc.forkOnIO</literal>.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>-qw</option></term>
+ <indexterm><primary><option>-qw</option></primary><secondary>RTS
+ option</secondary></indexterm>
+ <listitem>
+ <para>Migrate a thread to the current CPU when it is woken
+ up. Normally when a thread is woken up after being
+ blocked it will be scheduled on the CPU it was running on
+ last; this option allows the thread to immediately migrate
+ to the CPU that unblocked it.</para>
+
+ <para>The rationale for allowing this eager migration is
+ that it tends to move threads that are communicating with
+ each other onto the same CPU; however there are
+ pathalogical situations where it turns out to be a poor
+ strategy. Depending on the communication pattern in your
+ program, it may or may not be a good idea.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>