TSO

[John-Mark Gurney]

Julian Elischer wrote this message on Fri, Feb 28, 2014 at 13:24 +0800:
> On 2/27/14, 5:24 AM, John-Mark Gurney wrote:
> >Jack Vogel wrote this message on Wed, Feb 26, 2014 at 10:27 -0800:
> >>Drivers have to work with whatever the requirements/limitations of the
> >>hardware,
> >>if you have a 5 lb sack you shouldn't be surprised if some drops when you
> >>shove
> >>6 lbs at it :)
> >But right now, when that happens, the nic just drops it instead of
> >telling the kernel to stop giving 6 lbs sacks.. :)  It's only after a
> >large amount of work by various people did we even find out that this
> >is what was happening...
> so why not look at what would happen if it were people doing this..
> 
> person1 would hand person2 a 4 pound sack.
> all ok..
> person 1 then hands person2 a 6 pound sack and person 2 replies
> "Ouch", that's too much!..
> person 1 now knows not to do that.. until he forgets...
> part of the trick is knowing while assembling the packet, what 
> interface is going to be used..
> which from memory is not 100% guaranteed because routes can change...

Umm... TSO depends upon knowlege that the interface supports it...
if it didn't we couldn't do it..  The default is that the person can
only ever accept a 1lb bag, but the TSO flag says, they can take more..

If they forget, then they'd go back to the default of 1lb sacks at
a time...

Plus, we already have something similar for the max size of the TSO,
so the code is mostly there already, see t_tsomax...

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."