Re: RFC: TSO patch for current

On Fri, 1 Sep 2006, Jack Vogel wrote:

> This is a patch for the stack and the em driver to enable TSO on CURRENT. 
> Previously I had problems getting it to work, but this is functional.
>
> I should note that CURRENT is being a pain right now, when I comment out em 
> in the config the kernel panics coming up, so I had to substitute this code 
> into the tree. Rather bizarre :)
>
> I have this functionality running on a 6.1 based system, and our test group 
> is already testing against that driver, so far things are looking good.
>
> I have designed it so the driver can continue to be built without support. 
> There is also a sysctl in the stack code so you can set 
> net.inet.tcp.tso_enable on or off and compare.
>
> I know there may be some refinements to add in, but I would like to get this 
> into CURRENT as a start.

Per my earlier comments, I would like to see the issue of doing an on-demand 
segmentation of TCP at the IP layer in the event that the early route decision 
becomes stale (i.e., ipfw fwd, ipsec, etc), as occurs in the NetBSD code. 
Likewise, I think Andre's comment about making the routing decision up front 
for the TCP connection as part of the existing search for PMTU information 
makes sense.  I'm more interested in seeing the former addressed than the 
latter before the commit, though, which can quite easily follow.

Robert N M Watson
Computer Laboratory
University of Cambridge