On Fri, Sep 12, 2014 at 4:11 AM, Sourav <sourav.chakraborty@xxxxxxxxxxxxxxxxxxx> wrote: > On 11/09/14 00:14, Helmut Schaa wrote: >> >> On Wed, Sep 10, 2014 at 10:42 AM, Arend van Spriel <arend@xxxxxxxxxxxx> >> wrote: >>> >>> On 09/10/14 03:26, Sourav wrote: >>>> >>>> We are using Ralink chip Rt3072L (using rt2800usb drivers rt2800usb.c), >> >> The Ralink USB hardware is quite bad in reporting TX status and as >> such minstrel_ht cannot do proper rate selection. >> If you watch the rc stats at >> >> /sys/kernel/debug/ieee80211/phy0/netdev\:wlan0-0/stations/xx:xx:xx:xx:xx:xx/rc_stats >> you might see a lot of rate selection "hopping". >> >> Regards. >> Helmut > > please take a look at the attachments.... the first one shows the rc_stats > and iperf stats side by side on the router(iperf is running in client mode > in the router).....the second attachment is from a laptop which is running > iperf in server mode. > > I don't see a lot of rate "hopping" in the rc_stats file, (T,t and P) rates > are pretty much stable.... yet there is a big difference between those rates > and the throughput using iperf...... Indeed, rc_stats looks acceptable. > when you say "Ralink USB hardware is quite bad in reporting TX status", do > you mean that the HW reports less tx rate to minstrel_ht and so its rate > calculation is screwed up? The HW sometimes does not report the status of transmitted frames correctly. The TX status register is a FIFO of 16 (or similar) elements and if the driver is not reading it "fast enough" the FIFO will overflow :( at least that was the point when I was looking at the ralink hardware last time. Not sure if something changed recently. > Can you please let me know the section of code inside Rc_80211_minstrel_ht.c > (or somewhere else) which deals with getting the tx rate from ralink HW? There is no special code in minstrel(_ht) in regard to rt2x00. Are you able able to get some statistics on the receiver side (your windows machine) regarding TX rates and AMPDU lengths? Helmut -- 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
