AIX

Hi,

we've a gigabit Ethernet adapter. And we wanted to improve the performance by tuning network parameters. so' as per IBM info center,
we tried changing the tuning parameters on the fly (temporarily) using ifconfig command. But it didnt work.

so we had to bring down the interface and run chdev commands along with parameters.
and through smitty, changed MTU & enabled the jumbo frames.

tcp_sendspace, tcp_recvspace, rfc1323 & MTU etc.


after that, i bought up the interface, i can see all the latest settings.
i mean when i ran

Code:

ifconfig -a

it is giving the updated info.

My question here is,
Do i still need to update the same settings using

Code:

no

command ?
why because interface is showing all the updated info, where as

Code:

no -a

command showing default values.

we just followed the IBM steps according to the above IBM link.
Can you please give me some idea.

There are several tuning parameters for the kernel/network stack. The commands to set and query these "tunables" in IBM speak are:

no
schedo
vmo
ioo

All these commands share the same syntax:
-a display the current settings (even the defaults)
-o set the respective parameter
-p make the change of the parameter permanent

The way by which the commands work is: there is a directory /etc/tunables in which two files reside: nextboot and lastboot. Every tuning parameter which is not default will be listed in one of these. lastboot only holds the current values and at boot time it is overwritten by a copy of nextboot. If you change a parameter for the current boot cycle the change will be reflected there. If you choose to make a change permanent it gets written into nextboot and will be made active with the next boot.

You can edit nextboot with any plain text editor, but it is not wise to edit lastboot. Use the commands instead because they will also make the changes you intend active by restarting the respective services/daemons/... .

I hope this helps.

bakunin

chdev command is only for that adapter's interface (enX).
Whereas no will set the network tuning parameter across the board.

Example: If you have two interfaces (one primary 'entX', one for backups 'entY'), if you use no command the settings are reflected on both adapters interfaces (entX & entY). But if you use chdev -l entX -a XXX this setting is only reflected on the interface (enX) of that particular adapter (entX), and not on other adapter's interface.

Hope this make sense.