This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] networking checksum errors again

Jason wrote:
w00t! That fixed it. I read your email on the logic for not doing the tcp checksums and, while I am by no means in possesion of the brains the developers have, I am left wondering why that
decision was made.  Would anyone care to comment?

I think I missed a post somewhere along this thread...

Which decision are you referring to? Avoiding the
TCP checksum between domains? The rationale for not
doing the checksum is that it is a significant savings
in performance. Even for traffic that goes out to
a public net and must contain a checksum, deferring
it to dom0 when the OS can offload it to the physical
NIC (most NICs these days are capable of computing the
checksums in hardware) is a significant saving.

The native Linux stack offloads the calculation of
the checksum to the NIC, and not doing so in the virtual
environment increases the gap when comparing Xen to
bare metal Linux.

There are a lot of other issues here to resolve, of
course, and fixing some of the current issues is being
worked. It's likely going to be an issue for discussion
when we're up for mainline inclusion.


Xen-devel mailing list

<Prev in Thread] Current Thread [Next in Thread>