[Cake] making split_gso_threshold configurable

[Toke Høiland-Jørgensen]

Dave Taht <dave.taht at gmail.com> writes:

> On Wed, Jul 25, 2018 at 3:07 AM Sebastian Moeller <moeller0 at gmx.de> wrote:
>>
>> Hi Toke,
>>
>>
>> > On Jul 25, 2018, at 12:02, Toke Høiland-Jørgensen <toke at toke.dk> wrote:
>> >
>> > Dave Taht <dave.taht at gmail.com> writes:
>> >
>> >> I really wanted cake to always optimize for low latency. I wanted it
>> >> to "just work" at line rate on dsl, on 100mbit, even 10mbit ethernet,
>> >> to work against pause frames, etc, without configuration. I wanted to
>> >> defeat drivers like the mvneta that can do 64k of software GRO
>> >> automagically.
>> >
>> > So I think that Eric's point was that the GSO logic itself should
>> > throttle back and not build so big packets when the link rate is lower.
>> > Might be worth it to check if this is actually the case, and if not to
>> > get GSO fixed rather than disabling it.
>
> It doesn't and I think I should just put forth the patch and face the
> howling from the 40gbit guys.

Well, feel free I guess? :)

>> > Also, are there actually any modems that will negotiate ethernet line
>> > rates less than a gigabit?
>>
>>         Yes, there are XDSL Modem(routers) that only have
>>         fast-ethernet ports. Not sure how rare these are though.
>
> And there are also many devices that ecert hardware flow control.

But why would you ever run with such a device in a setup where flow
control gets a chance to kick in? Wouldn't you turn on the shaper anyway
(in which case you already get GSO splitting)?

-Toke