From 5707bfdf0aac985e8e82c9a5004eb458d1d79801 Mon Sep 17 00:00:00 2001
From: =?utf-8?q?Dan=20Hor=C3=A1k?= <dan@danny.cz>
Date: Fri, 30 Oct 2009 11:23:08 +0100
Subject: [PATCH] update readahead value for better performance

Description: dasd,zfcp: Add udev rule to set increased "default max readahead"
Symptom:     Sequential read performance on disks is not as good as it could be.
Problem:     The current "default max readahead" defined by the kernel is too
             small for s390 (128 kb).
Solution:    Add udev rule to set a better default value (512 kb). This will
             increase sequential read performance up to 40%.
---
 etc/udev/rules.d/60-readahead.rules |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)
 create mode 100644 etc/udev/rules.d/60-readahead.rules

diff --git a/etc/udev/rules.d/60-readahead.rules b/etc/udev/rules.d/60-readahead.rules
new file mode 100644
index 0000000..3133c66
--- /dev/null
+++ b/etc/udev/rules.d/60-readahead.rules
@@ -0,0 +1,13 @@
+#
+# Rules to set an increased default max readahead size for s390 disk devices
+# This file should be installed in /etc/udev/rules.d
+#
+
+SUBSYSTEM!="block", GOTO="ra_end"
+
+ACTION!="add", GOTO="ra_end"
+# on device add set initial readahead to 512 (instead of in kernel 128)
+KERNEL=="sd*[!0-9]", ATTR{queue/read_ahead_kb}="512"
+KERNEL=="dasd*[!0-9]", ATTR{queue/read_ahead_kb}="512"
+
+LABEL="ra_end"
-- 
1.6.3.3