[Xen-devel] "tcp: refine TSO autosizing" causes performance regression on Xen

[Eric Dumazet]

On Mon, 2015-04-13 at 11:56 +0100, George Dunlap wrote:

> Is the problem perhaps that netback/netfront delays TX completion?
> Would it be better to see if that can be addressed properly, so that
> the original purpose of the patch (fighting bufferbloat) can be
> achieved while not degrading performance for Xen?  Or at least, so
> that people get decent perfomance out of the box without having to
> tweak TCP parameters?

Sure, please provide a patch, that does not break back pressure.

But just in case, if Xen performance relied on bufferbloat, it might be
very difficult to reach a stable equilibrium : Any small change in stack
or scheduling might introduce a significant difference in 'raw
performance'.