[CentOS] Sysctl on Kernel 2.6.18-128.1.16.el5

Sysctl Values
-------------------------------------------
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216
net.ipv4.tcp_window_scaling = 1

# vm.max-readahead = ?
# vm.min-readahead = ?

# HW Controler Off
# max-readahead = 1024
# min-readahead = 256

# Memory over-commit 
# vm.overcommit_memory=2
# Memory to activate bdflush
# vm.bdflush="40 500 0 0 500 3000 60 20 0"
--------------------------------------------

What's the deal with the options with the "#"? Is the current kernel not
supported any more? The ones not commented still work. I did not seem to
notice this until migrating settings from a 5 machine not 5.1 but "5". I
hate to ask such a dumb question but there seems to be no info from Up
The Road Either.

Error:
sysctl -w "vm.min-readahead=256"
error: "vm.min-readahead" is an unknown key

Further more nothing is related in here[1] due to kernel parameter
related changes.

[1] http://www.centos.org/docs/5/html/release-notes/    \
RELEASE-NOTES-U3-en.html#sect-Release_Notes-Kernel_Related_Updates


John