Pkshih <pkshih@xxxxxxxxxxx> 於 2021年5月14日 週五 下午2:08寫道： > > > > -----Original Message----- > > From: 邱名碩 [mailto:ccchiu77@xxxxxxxxx] > > Sent: Monday, May 10, 2021 4:36 PM > > To: Pkshih; Andy Huang; Larry.Finger@xxxxxxxxxxxx; kuba@xxxxxxxxxx; kvalo@xxxxxxxxxxxxxx; Reto > > Schneider; linux-wireless@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > > Subject: How does the rate adaptive mask work on Realtek WiFi driver > > > > Hi guys, > > I had a problem while verifying the ampdu tx throughput with the > > rtl8xxxu driver on RTL8188CUS module. The throughput number is > > relatively good, 39~42Mbps TCP on 2.4GHz channel. However, the > > retransmission rate is high, it's 15% ~ 21% with rtl8xxxu driver and > > It's almost the same result with the rtl8192cu driver. I can get > > averagely 7~10% retransmission rate in the same test bed with Realtek > > vendor driver. > > > > From the air capture, I can see the rtl8xxxu driver keep sending > > the aggregated frames in MCS7 and doesn't even fall back to lower MCS > > index in the subsequent retries. I can only see very few retried > > packets been sent with MCS0 or 6Mbps grate. On the vendor driver, I'll > > see the retried ampdu packets with MCS4 after 3 retries w/o ack from > > the receiver. > > > > From the rate mask command issued by the h2c command, I force both > > the rtl8xxxu driver and vendor driver to use the same ratemask 0xfffff > > (MCS 0-7 and b/g rate included) and leave the arg0 as-is (mostly 0xa0) > > and I expect both drivers can do the rate adaptive thing in the same > > way, but it seems to make no difference. The rtl8xxxu driver still > > sends the packets with highest MCS. > > > > Can anyone tell me what should I expect the rate adaptive to work > > with the rate mask 0xfffff and 0xf0000? Does the 0xf0000 means that it > > will pick up a tx rate only between nrate MCS4 to MCS7? I need a base > > line so that I can judge it's simply a rate mask problem or maybe the > > h2c command is not written correctly. Please kindly suggest what I > > should do next. Thanks > > > > The rate mask indicates which rates will be used by rate adaptive mechanism. > I'm not sure the exact bit allocation for CCK/OFDM/MCS, maybe > 0x0000f/0x00ff0/0xff0000 for CCK/OFDM/MCS respectively, but you can trace > vendor driver to know the detail. > > I suggest you can try to send only OFDM rate mask, and expect to see OFDM > rate only by your sniffer. If it's still keep on MCS7, rate adaptive may > not work properly. > Thanks. That's my expectation and I'll try to verify it on vendor driver and upstream rtl8192cu driver. > Also, you can compare the content of rate adaptive H2C with vendor driver to > see if the format is correct. > > Another thing is to try 'fix_rate' in tx_desc. Check the vendor driver to > know the use_rate/rate/bw fields of tx_desc. Then, try to fix the rate you > want. > If I set the fix_rate in tx_desc, will the rate mask in H2C command be ignored? Or the underlying firmware will do the tx rate fallback for the retry packets? Chris > -- > Ping-Ke >
