svn commit - mysqldoc@oter02: r25755 - trunk/refman-5.6

[john.russell]

Author: jdrussel
Date: 2011-04-06 08:15:27 +0200 (Wed, 06 Apr 2011)
New Revision: 25755

Log:
Clarified guidance on innodb_purge_thread, when to increase the value or
keep it at or near 1.


Modified:
   trunk/refman-5.6/innodb-performance.xml
   trunk/refman-5.6/se-innodb-core.xml


Modified: trunk/refman-5.6/innodb-performance.xml
===================================================================
--- trunk/refman-5.6/innodb-performance.xml	2011-04-06 06:07:27 UTC (rev 25754)
+++ trunk/refman-5.6/innodb-performance.xml	2011-04-06 06:15:27 UTC (rev 25755)
Changed blocks: 2, Lines Added: 14, Lines Deleted: 14; 2497 bytes

@@ -1845,10 +1845,9 @@
     </indexterm>
 
     <para>
-      Starting in InnoDB 1.1 with MySQL 5.5, the
-      <link linkend="glos_purge">purge</link> operations (a type of
+      The <link linkend="glos_purge">purge</link> operations (a type of
       garbage collection) that InnoDB performs automatically can be done
-      in a separate thread, rather than as part of the
+      in one or more separate threads, rather than as part of the
       <link linkend="glos_master_thread">master thread</link>. This
       change improves scalability, because the main database operations
       run independently from maintenance work happening in the

@@ -1857,20 +1856,21 @@
 
     <para>
       To enable this feature, set the configuration option
-      <literal>innodb_purge_threads=1</literal>, as opposed to the
-      default of 0, which combines the purge operation into the master
-      thread.
+      <literal>innodb_purge_threads=<replaceable>n</replaceable></literal>,
+      as opposed to the default of 0, which combines the purge operation
+      into the master thread. If DML action is concentrated on a single
+      table or a few tables, keep the setting low so that the threads do
+      not contend with each other for access to the busy tables. If DML
+      operations are spread across many tables, increase the setting.
+      Its maximum is 32.
     </para>
 
     <para>
-      You might not notice a significant speedup, because the purge
-      thread might encounter new types of contention; the single purge
-      thread really lays the groundwork for further tuning and possibly
-      multiple purge threads in the future. There is another new
-      configuration option, <literal>innodb_purge_batch_size</literal>
-      with a default of 20 and maximum of 5000. This option is mainly
-      intended for experimentation and tuning of purge operations, and
-      should not be interesting to typical users.
+      There is another related configuration option,
+      <literal>innodb_purge_batch_size</literal> with a default of 20
+      and maximum of 5000. This option is mainly intended for
+      experimentation and tuning of purge operations, and should not be
+      interesting to typical users.
     </para>
 
     <para>


Modified: trunk/refman-5.6/se-innodb-core.xml
===================================================================
--- trunk/refman-5.6/se-innodb-core.xml	2011-04-06 06:07:27 UTC (rev 25754)
+++ trunk/refman-5.6/se-innodb-core.xml	2011-04-06 06:15:27 UTC (rev 25755)
Changed blocks: 1, Lines Added: 2, Lines Deleted: 1; 703 bytes

@@ -11744,7 +11744,8 @@
             reduce internal contention within InnoDB, improving
             scalability. Increasing the value to greater than 1 creates
             that many separate purge threads, which can improve
-            efficiency on systems with extra CPU capacity.
+            efficiency on systems where DML operations are performed on
+            multiple tables. The maximum is 32.
           </para>
         </listitem>