TSO not working?

[Thor Lancelot Simon <tls%panix.com@localhost>]

On Fri, Oct 28, 2011 at 06:54:31PM +0200, Manuel Bouyer wrote:
> On Fri, Oct 28, 2011 at 12:30:57PM -0400, Thor Lancelot Simon wrote:
> > I'd say turn off WM_F_NEWQUEUE -- assuming that works -- and commit.
> 
> I'll look at this.
> 
> > 
> > While you're in there, can you see whether we're actually feeding
> > the TSO enough data at once that it's actually useful?  The tcpdump
> > makes me suspect for some reason, we may not be.
> 
> I added a sc_ev_txlargetso, which gets incremented by:
>       if (m0->m_pkthdr.len > 32768)
>               WM_EVCNT_INCR(&sc->sc_ev_txlargetso);

It'd be interesting, perhaps, to see how often we were actually even > 1500.

> ttcp -t -l65536 -b524288 -D xen1-priv < /glpool/truc
> 
> (64k writes but a 512k TCP buffer) I get no "largetso".

Does the window ever have 32K of space, I wonder?  Maybe the delay is
not large enough to ever let it open that wide.

Thor