linux-kernel - Re: How does the rate adaptive mask work on Realtek WiFi driver

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Message-ID: <CANgQ54f4QAMmGE-swSQoXHoZQNSX166afqTaCoKW-DN=0jdihg@mail.gmail.com>
Date:   Mon, 10 May 2021 13:58:56 +0800
From:   邱名碩 <ccchiu77@...il.com>
To:     Pkshih <pkshih@...ltek.com>, Andy Huang <tehuang@...ltek.com>,
        Larry.Finger@...inger.net, kuba@...nel.org, kvalo@...eaurora.org,
        Reto Schneider <reto.schneider@...qvarnagroup.com>,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: How does the rate adaptive mask work on Realtek WiFi driver

邱名碩 <ccchiu77@...il.com> 於 2021年5月10日 週一 下午1:57寫道：
>
> 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
>
> Chris