On Mon, Apr 8, 2013 at 12:38 PM, Johannes Berg
<johannes@xxxxxxxxxxxxxxxx> wrote:
> On Mon, 2013-04-08 at 12:30 -0700, Thomas Pedersen wrote:
>
>> OK those functions are exported to the drivers. The 'enum
>> queue_stop_reason' is defined in ieee80211_i.h, so the driver wouldn't
>> be able to interpret them anyway?
>
> Oh, you're way underestimating the creativity of driver authors :-)
>
>> Would you prefer a utility function internal to mac80211 which does
>> return the reason,
>
> That seems fine, although a bit more inefficient?
>
>> or just the following pattern?
>>
>> if (ieee80211_queue_stopped(hw, queue)) {
>> qreason = hw_to_local(hw)->queue_stop_reasons[queue];
>> if (qreason & ~(ALLOWED_QUEUE_STOP_REASONS))
>> something;
>> }
>
> That seems racy? Even asking whether it's stopped is racy though, what
> are you even trying to accomplish?
Yeah, that's why I'd like to get the reason the first time.
_h_mesh_fwding() checks whether the outgoing queue is stopped, to
avoid piling frames on the pending queue if the outgoing medium is
busy. I guess the idea was to avoid queueing frames faster than the
hardware could unload them. Maybe this doesn't actually happen, but we
can be a little bit smarter about when to drop forwarded frames. Like
if skbs are just being added to the outgoing queue, we probably
shouldn't.
This patch and the next one show a small improvement in throughput and
loss % in the forwarding path.
--
Thomas
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