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

Lee Revell
2004-08-24T05:02:46Z

On Mon, 2004-08-23 at 23:56, K.R. Foley wrote:
> 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
>

I have some that are similar to this. Looks like many of the
differences are due to different network drivers (e100 vs via-rhine).

> 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/
>

Looks like except for the one above, all of these involve the
extract_entropy issue. I am using a hack to disable the random driver
to avoid these latencies.

There are a few other threads going on discussing a real solution to the
extract_entropy issue. However, none of the solutions that has been
posted yet fix the problem.

Lee