Re: [Make-wifi-fast] [RFC/RFT 5/5] ath9k: Count RX airtime in airtime deficit

[Adrian Chadd <adrian@freebsd.org>]

On 5 June 2016 at 03:55, Toke Høiland-Jørgensen <toke@toke.dk> wrote:
> Adrian Chadd <adrian@freebsd.org> writes:
>
>> I've been working on something similar in freebsd, so cool to see this
>> happening here!
>
> Cool. Do you have code available somewhere?

not yet. It was mostly what you just did in ath9k anyway :)

The sample rate control module and net80211 already had the duration
calculation bits, and I was just trying to figure out how to track it
per-node in a useful way without blowing CPU time.

>
>> The only thing missing atm is STBC and LDPC. My RX airtime code looks
>> basically like this one too; but I have TODO items for ensuring
>> LDPC/STBC calculations are sane.
>
> So basically this means taking into account whether there was MIMO in
> use (which may lower the transmit time)? My understanding is that (at
> least in Linux) this is encoded in the rate tables (i.e. a MIMO rate is
> a separate entry). Am I wrong in thinking so? Or is this something else
> entirely?

The existing routines take GI, MCS rate, channel width; figure out
MIMO, and do the math. The assumption is the symbol count is the same.
For STBC I think there's an additional symbol at the end (because it's
mixed current symbol plus previous symbol.) I forget the details for
LDPC.

I'll er, go read the standard again. :)


-adrian