On 2012-10-30 2:00 PM, Mathias Kretschmer wrote: > On 10/30/2012 01:43 PM, Felix Fietkau wrote: >> On 2012-10-30 1:07 PM, Simon Wunderlich wrote: >>> From: Mathias Kretschmer <mathias.kretschmer@xxxxxxxxxxxxxxxxxxx> >>> >>> According to 802.11-2007 17.3.8.6 (slot time), the slot time should >>> be increased by 3 us * coverage class. The code only increased the >>> ack timeout, which is fixed by this patch. >>> >>> We have noticed in our long shot scenario that we see less collisions >>> with this patch. >> At some point I had the slot time increase in the driver, but noticed a >> massive throughput degradation on 10-20 km links. Leaving the slot time >> alone and changing only the ACK timeout fixed this. What distances did >> you test? > > about 11km. did you test UDP (unidirectional) or TCP (bidirectional) throughput ? I always use TCP, because UDP tests are too unrealistic to estimate real performance. > The larger slot time will increase the channel access overhead which should impact > unidirectional throughput. > > With bidirectional traffic, the larger slottime should help to minimize collisions > on loaded links. Overall this seems to increase the net throughput for us, > especially in higher access categories (smaller backoff windows). When I ran the test, the throughput degradation was so big that the links became almost useless. It was a long time ago, so maybe this was caused by another bug that has been fixed since. I will run another test with this patch in a current version... - Felix -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
