[CentOS] Sysctl on Kernel 2.6.18-128.1.16.el5

On Tue, 2009-07-07 at 16:54 -0400, JohnS wrote:
> 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
---
/proc/sys/vm/max-readahead:
Appears that I need blockdev for that. But no info on the others.