Re: mac80211-hwsim and tx-rates.

[Ben Greear <greearb@candelatech.com>]

On 03/14/2015 10:48 AM, Bob Copeland wrote:
> On Sat, Mar 14, 2015 at 09:14:14AM -0700, Ben Greear wrote:
>> It can change with every packet based on rate-control logic, right?
>
> You said you wanted to go from index to bitrate -- the index changes,
> but not the rate<->index mapping.

The index means different things based on legacy, HT, VHT.  You need index
+ flags to determine the actual rate for each packet.

I am fine with hard-coding in user-space the correlation of legacy index
to rates.

The array that is currently sent to user-space is the rates that rate-ctrl
determines should be used for transmit (and re-transmit), as far as I can tell.


>> And, it seems unlikely to me that an extra 16 bytes or so would make a
>> great deal of difference.  Using hash tables instead of linear walks
>> and other things would likely improve performance more?
>
> Last time I tested with perf, memcpy dominated everything -- I've been
> thinking about having a mode where just headers are sent to userspace
> to avoid some of that.

I need full pkt in user-space, but at least for some use-cases your idea
may be a nice improvement.

With hundreds of virtual radios and network devices, hashing the lookup of
radios should be a big win.  I'll work on that someday soon most likely.

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com