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.

1 files changed, 1 insertions, 1 deletions

diff --git a/sys/kern/vfs_cluster.c b/sys/kern/vfs_cluster.c
index 1ab263c..469bc7e 100644
--- a/sys/kern/vfs_cluster.c
+++ b/sys/kern/vfs_cluster.c
@@ -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");