svn commit: r211031 - head/sys/kern

Ivan Voras ivoras at
Sat Aug 7 18:30:11 UTC 2010

Author: ivoras
Date: Sat Aug  7 18:30:10 2010
New Revision: 211031

  To help with sequential read UFS performance on modern systems, increase
  the vfs.read_max default. For most systems this means going from 128 KiB
  to 256 KiB, which is still very conservative and lower than what most
  other operating systems use, but as a sane default should not
  interfere much with existing systems.
  For systems with RAID volumes and/or virtualization envirnments, where
  read performance is very important, increasing this sysctl tunable to 32
  or even more will demonstratively yield additional performance benefits.
  If MAXPHYS ever gets bumped up, it will probably be a good idea to slave
  read_max to it.


Modified: head/sys/kern/vfs_cluster.c
--- head/sys/kern/vfs_cluster.c	Sat Aug  7 17:57:58 2010	(r211030)
+++ head/sys/kern/vfs_cluster.c	Sat Aug  7 18:30:10 2010	(r211031)
@@ -71,7 +71,7 @@ static int write_behind = 1;
 SYSCTL_INT(_vfs, OID_AUTO, write_behind, CTLFLAG_RW, &write_behind, 0,
     "Cluster write-behind; 0: disable, 1: enable, 2: backed off");
-static int read_max = 8;
+static int read_max = 16;
 SYSCTL_INT(_vfs, OID_AUTO, read_max, CTLFLAG_RW, &read_max, 0,
     "Cluster read-ahead max block count");

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