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From: Aditya Sarawgi <truncs@FreeBSD.org>
To: Perforce Change Reviews <perforce@FreeBSD.org>
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Subject: PERFORCE change 169103 for review
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http://perforce.freebsd.org/chv.cgi?CH=169103

Change 169103 by truncs@aditya on 2009/10/01 20:13:08

	Make the comment more verbose - include why these parameters were introduced
	in orlov block allocator.

Affected files ...

.. //depot/projects/soc2009/soc_ext2fs/src/sys/fs/ext2fs/fs.h#4 edit

Differences ...

==== //depot/projects/soc2009/soc_ext2fs/src/sys/fs/ext2fs/fs.h#4 (text+ko) ====

@@ -57,15 +57,26 @@
 /*
  * The path name on which the file system is mounted is maintained
  * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in 
- * the super block for this name. AVFPDIR is the expected number of
- * files per directory. AVGDIRSIZE is obtained by multiplying AVFPDIR
- * and AVFILESIZ which is assumed to be 16384. Both AVFPDIR and AVFFIZSIZ
- * are taken from UFS and they are used in implementation of Orlov Block
- * Allocator.
+ * the super block for this name. 
  */
 #define MAXMNTLEN	512
+
+/*
+ * Grigoriy Orlov <gluk@ptci.ru> has done some extensive work to fine
+ * tune the layout preferences for directories within a filesystem.
+ * His algorithm can be tuned by adjusting the following parameters
+ * which tell the system the average file size and the average number
+ * of files per directory. These defaults are well selected for typical
+ * filesystems, but may need to be tuned for odd cases like filesystems
+ * being used for sqiud caches or news spools.
+ * AVFPDIR is the expected number of files per directory. AVGDIRSIZE is 
+ * obtained by multiplying AVFPDIR and AVFILESIZ which is assumed to be 
+ * 16384.
+ */
+
 #define AFPDIR		64
 #define AVGDIRSIZE	1048576
+
 /*
  * Macros for access to superblock array structures
  */