kern/154428: xn0 network interface and PF - Massive performance drop

[Alex]

I stumbled across PR 135178, perhaps there is some relationship with 
these PR's, though the reporter of that PR has not responded in some time.

On 02/13/11 15:31, Colin Percival wrote:
> On 02/12/11 20:18, Alex wrote:
>> Fixed by net.inet.tcp.tso: 1 ->  0
>>
>> but why?? found this by trial an error.  setting net.inet.tcp.tso to 0
>> with pf enabled gives good performance, if i set it to 1, speeds plumet
>> to below dialup!
> There have been problems with Xen and TSO in the past relating to how much
> data gets handed off to the hypervisor at once... why this would cause issues
> only with PF, I have no idea, though.
>