Robert Watson wrote:
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.
In the patch I posted yesterday into this thread the TSO decision is
done at connection setup time in tcp_mss() where all other initial TCP
connection parameters are initilized as well. If the same interface
we took the MTU values from, is found to support TSO it gets enabled for
this connection too. Should the egress interface change during the
lifetime of the connection and the new one doesn't support TSO we get
an EMSGSIZE error from ip_output(), disable TSO for this connection and
have tcp_output() resend the data again while doing the segmentation
itself as usual. Should the connection change back to the TSO capable
interface later on we don't re-enable TSO for the connection though.
OTOH having a bulk transfer TCP session (where TSO actually helps) migrate
between interface is a *very* rare occurence and not worth special casing
for it.
--
Andre
_______________________________________________
freebsd-net@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-net
To unsubscribe, send any mail to "[EMAIL PROTECTED]"
