Re: Network performance degradation from 2.6.11.12 to 2.6.16.20

Jesper Dangaard Brouer
2006-06-19T18:24:12Z

On Mon, 19 Jun 2006, Andi Kleen wrote:

>> If you use "pmtmr" try to reboot with kernel option "clock=tsc".
>
> That's dangerous advice - when the system choses not to use
> TSC it often has a reason.

Sorry, it was not a general advice, just something to try out. It really
solved my network performance issue...

>> On my Opteron AMD system i normally can route 400 kpps, but with
>> timesource "pmtmr" i could only route around 83 kpps. (I found the timer
>> to be the issue by using oprofile).
>
> Unless you're using packet sniffing or any other application
> that requests time stamps on a socket then the timer shouldn't
> make much difference. Incoming packets are only time stamped
> when someone asks for the timestamps.

I do not know what caused the issue on my machine, but I can look into it
if you like to know?

I do have VLAN interfaces on the machine and it seems that eth1 runs in
PROMISC mode (eth1.xxx does not). Could it be caused by that?

Hilsen
Jesper Brouer

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MSc. Master of Computer Science
Dept. of Computer Science, University of Copenhagen
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