Re: [RFC v3] mac80211: Optimize scans on current operating channel.

[Ben Greear <greearb@candelatech.com>]

On 01/28/2011 05:20 AM, Johannes Berg wrote:
> On Thu, 2011-01-27 at 10:33 -0800, Ben Greear wrote:
>
>>>> @@ -396,10 +397,14 @@ ieee80211_rx_h_passive_scan(struct ieee80211_rx_data *rx)
>>>>    		return ieee80211_scan_rx(rx->sdata, skb);
>>>>
>>>>    	if (test_bit(SCAN_SW_SCANNING,&local->scanning)) {
>>>> -		/* drop all the other packets during a software scan anyway */
>>>> -		if (ieee80211_scan_rx(rx->sdata, skb) != RX_QUEUED)
>>>> +		ret = ieee80211_scan_rx(rx->sdata, skb);
>>>> +		/* drop all the other packets while scanning off channel */
>>>> +		if (ret != RX_QUEUED&&
>>>> +		    test_bit(SCAN_OFF_CHANNEL,&local->scanning)) {
>>>>    			dev_kfree_skb(skb);
>>>> -		return RX_QUEUED;
>>>> +			return RX_QUEUED;
>>>> +		}
>>>> +		return ret;
>>>
>>> Alright -- but does the mlme.c code know not to expect beacons during an
>>> on-channel scan?
>>
>> I have a more basic question on this:
>>
>> Should we just pass all packets on up the stack, regardless of whether we are
>> offchannel or not?  I think that would simplify things here,
>> and if/when we ever support things other than just scanning on
>> different off-channels, that code would just work.
>
> I'm not really exactly sure why we don't.
>
> However -- I was thinking of something else, not data packets. While
> scanning, all received beacons will be handed to the scan code. But if
> the mlme code isn't told to stop looking for them, it'll still expect to
> see the beacons.

Currently, it seems mlme timers are stopped when we start scanning,
and then started when scanning is complete.

However, I don't see any similar effort in the work_work() method
when it goes off-channel.

Should we move the timer pause & restart logic into the offchannel_stop_vifs
and offchannel_return methods?

If that seems like a good idea, I'll attempt that as a follow on patch.

I don't think my changes make this any worse, so not critical to add this
to the current patch I'm working on.

Thanks,
Ben

>
> johannes


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