FreeBSD Handbook: config: Tuning Disks: a buggy section?

marju ignatjeva marju at bsd.ee
Mon Jul 26 18:15:53 UTC 2004


Hi, I am translating the handbook (at least some of it) into Estonian,
step by step and it seems the Configuration and Tuning chapter includes a
contradiction or some kind of buggy section at

http://www.ee.freebsd.org/doc/en_US.ISO8859-1/books/handbook/configtuning-disk.html

right under the subtitle "11.12.1.1 vfs.vmiodirenable":

the diff file: diff -u -p -r1.1 -r1.161 shows the following:

       <sect3>
-	<title>vfs.vmiodirenable</title>
-
-	<indexterm><primary>vfs.vmiodirenable</primary></indexterm>
-
+	<title><varname>vfs.vmiodirenable</varname></title>
+
+	<indexterm>
+	  <primary><varname>vfs.vmiodirenable</varname></primary>
+	</indexterm>
+
 	<para>The <varname>vfs.vmiodirenable</varname> sysctl variable
-	  defaults to 0 (off) (though soon it will default to 1) and may
-	  be set to 0 (off) or 1 (on).  This parameter controls how
-	  directories are cached by the system.  Most directories are
-	  small and use but a single fragment (typically 1K) in the
-	  filesystem and even less (typically 512 bytes) in the buffer
-	  cache.  However, when operating in the default mode the buffer
+	  may be set to either 0 (off) or 1 (on); it is 1 by default.
+	  This variable controls how directories are cached by the
+	  system.  Most directories are small, using just a single
+	  fragment (typically 1 K) in the file system and less
+	  (typically 512 bytes) in the buffer cache.
+	  However, when operating in the default mode the buffer
 	  cache will only cache a fixed number of directories even if
 	  you have a huge amount of memory.  Turning on this sysctl
 	  allows the buffer cache to use the VM Page Cache to cache the
-	  directories.  The advantage is that all of memory is now
-	  available for caching directories.  The disadvantage is that
+	  directories, making all the memory available for caching
+	  directories.


It seems to me the default has been changed to 1 _but_ the text about the
previous default, 0, has not been replaced.

I am sending my version of how this section could be changed (my own
version diffed against the current revision):

--- r1.161      Mon Jul 26 18:06:41 2004
+++ conf.fix    Mon Jul 26 18:12:22 2004
@@ -1566,18 +1566,18 @@
          system.  Most directories are small, using just a single
          fragment (typically 1 K) in the file system and less
          (typically 512 bytes) in the buffer cache.
-         However, when operating in the default mode the buffer
+         With this variable turned off (to 0), the buffer
          cache will only cache a fixed number of directories even if
-         you have a huge amount of memory.  Turning on this sysctl
+         you have a huge amount of memory. When turned on (to 1), this
	  sysctl
          allows the buffer cache to use the VM Page Cache to cache the
          directories, making all the memory available for caching
          directories.  However,
          the minimum in-core memory used to cache a directory is the
          physical page size (typically 4 K) rather than 512 
-         bytes.  We recommend turning this option on if you are running
+         bytes.  We recommend keeping this option on if you are running
          any services which manipulate large numbers of files.  Such
          services can include web caches, large mail systems, and news
-         systems.  Turning on this option will generally not reduce
+         systems. Keeping on this option will generally not reduce
          performance even with the wasted memory but you should
          experiment to find out.</para>
       </sect3>



all the best
Marju Ignatjeva



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