Re: [patch] voluntary-preempt-2.6.8.1-P8

K.R. Foley
2004-08-24T03:57:07Z

Lee Revell wrote:
> On Mon, 2004-08-23 at 17:01, Ingo Molnar wrote:
>
>
>> - reduce netdev_max_backlog to 8 (Mark H Johnson)
>>
>
>
> On my system this setting has absolutely no effect on the skb related
> latencies. I tested setting netdev_max_backlog to every power of two
> between 1 and 128, and regardless of this setting, I can produce a
> 450-600 usec latency with:
>
> ping -s 65507 -f $DEFAULT_GATEWAY
>
> Looks like skb_checksum is the problem. Here is one of the traces:
>
> http://krustophenia.net/testresults.php?dataset=2.6.8.1-P8#/var/www/2.6.8.1-P8/trace14.txt
>
> Lee
>
> -

Setting netdev_max_backlog doesn't seem to have any effect for me either.

I get a similar latency when I try to reproduce your result above, ~612
usec. However, my trace is very different than yours:

http://www.cybsft.com/testresults/2.6.8.1-P8/latency_trace3.txt

In fact most any network activity, with the POSSIBLE exception of
already open connections, seem to be able to trigger higher latencies.
As you can see here:

http://www.cybsft.com/testresults/2.6.8.1-P8/

kr