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From:   =?UTF-8?B?6YKx5ZCN56Kp?= <ccchiu77@gmail.com>
Date:   Fri, 14 May 2021 12:26:58 +0800
Message-ID: <CANgQ54e_AkZQNYBBf4yrGGCQ-h+AE-ynM=RVD7Nxt9tY_mFKOQ@mail.gmail.com>
Subject: Re: How does the rate adaptive mask work on Realtek WiFi driver
To:     Pkshih <pkshih@realtek.com>, Andy Huang <tehuang@realtek.com>,
        Larry.Finger@lwfinger.net, kuba@kernel.org, kvalo@codeaurora.org,
        Reto Schneider <reto.schneider@husqvarnagroup.com>,
        linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org
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=E9=82=B1=E5=90=8D=E7=A2=A9 <ccchiu77@gmail.com> =E6=96=BC 2021=E5=B9=B45=
=E6=9C=8810=E6=97=A5 =E9=80=B1=E4=B8=80 =E4=B8=8B=E5=8D=884:35=E5=AF=AB=E9=
=81=93=EF=BC=9A
>
> 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 rtl8188cus vendor driver I tested is here (It can be compiled with
> kernel 5.12+)
> https://github.com/mschiu77/rtl8188cus_vendor/
>
> Chris

Gentle ping. Any suggestions would be appreciated.

Chris