Index: chap-tuning.xml
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RCS file: /cvsroot/htdocs/guide/en/chap-tuning.xml,v
retrieving revision 1.12
diff -b -u -r1.12 chap-tuning.xml
--- chap-tuning.xml     4 Apr 2007 08:08:05 -0000       1.12
+++ chap-tuning.xml     7 Apr 2007 10:15:17 -0000
@@ -1689,12 +1689,45 @@

      <para>
        LFS writes data to disk in a way that is sometimes too
-        aggressive and leads to congestion.
-       Information on how to throttle writing and finding the right
-        parameters are available
-       <ulink url="http://mail-index.NetBSD.org/tech-perform/2007/04/01/0000.html">this</ulink> and
-       <ulink url="http://mail-index.NetBSD.org/tech-perform/2007/04/01/0001.html">this</ulink> mail.
+        aggressive and leads to congestion. Blair Sadewitz has described
+       a good method for throttling writing and finding the right
+       parameters<footnote>
+         <para>
+           See
+           <ulink url="http://mail-index.NetBSD.org/tech-perform/2007/04/01/0000.html" /> and
+           <ulink url="http://mail-index.NetBSD.org/tech-perform/2007/04/01/0001.html" />.
      </para>
+       </footnote>.
+       The first step is to disable the sync delay, by setting the
+       following tunables through &man.sysctl.8;:
+      </para>
+
+      <programlisting>
+vfs.sync.delay = 0
+vfs.sync.filedelay = 0
+vfs.sync.metadelay = 0
+vfs.sync dirdelay = 0
+      </programlisting>
+
+      <para>
+       Then, find out how much bandwidth you have inside and outside
+       of the disk. This can be done by running
+       <command>newfs_lfs -ANF</command> on a partition close to
+       cylinder 0, and then on a partition close to the last cyclinder.
+       Average these two numbers, and calculate the LFS
+       <emphasis>page trip</emphasis> with the following formula:
+      </para>
+
+      <para>
+       <emphasis>t = (avg_bandwidth_in_bytes / PAGE_SIZE) / 4</emphasis>
+      </para>
+
+      <para>
+       Now you can set the <emphasis>vfs.lfs.pagetrip</emphasis> tunable
+       to <emphasis>t</emphasis> through &man.sysctl.8;.
+      </para>
+
+      <!-- XXX - Add note about BUFQ_PRIOCSCAN and BUFQ_READPRIO. -->
    </sect2>

  </sect1>

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