tcp_output starving -- is due to mbuf get delay?
silby at silby.com
Thu Apr 10 14:45:18 PDT 2003
On Thu, 10 Apr 2003, Borje Josefsson wrote:
> > > Have you tried running kernel profiling yet? It would be interesting to
> > > see which functions are using up the largest amount of time.
> Could do that if I knew how... Not before the weekend though, right now
> I'm at the longue at the airport...
I believe that the manpages regarding how to set it up were pretty useful,
it didn't take me long to get it operational last time I tried. However,
that was a while ago, so I can't give you any helpful tips.
> If everything is OK (which it apparently isn't), top will show free CPU,
> and netstat should show a *very* steady packet flow (around 90kpps if You
> have MTU 1500). Any packet loss is fatal for this speed, so if there is a
> way (as indicated by Mike above) to not restarting with windowsize from
> scratch that will make recovery much better.
Well, the packet loss I pointed out would be due to the ifqueue
overflowing, which could concieveably happen even if the actual network
wasn't congested. I don't have the equipment to create such a situation,
but it sounds like you might, in which case adding a debug printf or a
counter to see if it's happening might be advantageous.
Mike "Silby" Silbersack
More information about the freebsd-performance