Re: IPSEC disables TSO

On 8/16/07, Kip Macy <kip.macy_at_gmail.com> wrote:
> On 8/16/07, Andrew Gallatin <gallatin_at_cs.duke.edu> wrote:
> >
> > When tracking down an mxge 10GbE performance issue, I noticed that
> > simply compiling IPSEC into the kernel totally destroys 10GbE transmit
> > performance because it will silently disable TSO.
> >
> > The problem seems to be at least that the test on line 463 of
> > tcp_output.c (tp->t_inpcb->inp_sp == NULL) will always be
> > false.   If I comment that line out, TSO works as normal
> > (though I have no idea what would happen on an IPSEC connection).
> >
> > Is there some way to make this not happen?  I believe that the mxge
> > user simply wanted to run some handful of applications through ipsec
> > tunnels (perhaps even on a different NIC entirely).
>
> IPSEC encrypts the TCP header - how is the card going to do TSO?


I thought about this after sending and realized that the appropriate
response is that IPSEC needs to be careful to disable TSO when its in
use for a connection. What you're seeing was most likely done as an
expedient.

 -Kip