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    SubjectRe: RTL8723BE performance regression
    Date
    On Wed, 2018-05-02 at 05:44 +0000, Pkshih wrote:
    >
    > > -----Original Message-----
    > > From: João Paulo Rechi Vita [mailto:jprvita@gmail.com]
    > > Sent: Wednesday, May 02, 2018 6:41 AM
    > > To: Larry Finger
    > > Cc: Steve deRosier; 莊彥宣; Pkshih; Birming Chiu; Shaofu; Steven Ting; Chaoming_Li; Kalle Valo;
    > > linux-wireless; Network Development; LKML; Daniel Drake; João Paulo Rechi Vita; linux@endlessm.c
    > om
    > > Subject: Re: RTL8723BE performance regression
    > > 
    > > On Tue, Apr 3, 2018 at 7:51 PM, Larry Finger <Larry.Finger@lwfinger.net> wrote:
    > > > On 04/03/2018 09:37 PM, João Paulo Rechi Vita wrote:
    > > >>
    > > >> On Tue, Apr 3, 2018 at 7:28 PM, Larry Finger <Larry.Finger@lwfinger.net>
    > > >> wrote:
    > > >>
    > > >> (...)
    > > >>
    > > >>> As the antenna selection code changes affected your first bisection, do
    > > >>> you
    > > >>> have one of those HP laptops with only one antenna and the incorrect
    > > >>> coding
    > > >>> in the FUSE?
    > > >>
    > > >>
    > > >> Yes, that is why I've been passing ant_sel=1 during my tests -- this
    > > >> was needed to achieve a good performance in the past, before this
    > > >> regression. I've also opened the laptop chassis and confirmed the
    > > >> antenna cable is plugged to the connector labeled with "1" on the
    > > >> card.
    > > >>
    > > >>> If so, please make sure that you still have the same signal
    > > >>> strength for good and bad cases. I have tried to keep the driver and the
    > > >>> btcoex code in sync, but there may be some combinations of antenna
    > > >>> configuration and FUSE contents that cause the code to fail.
    > > >>>
    > > >>
    > > >> What is the recommended way to monitor the signal strength?
    > > >
    > > >
    > > > The btcoex code is developed for multiple platforms by a different group
    > > > than the Linux driver. I think they made a change that caused ant_sel to
    > > > switch from 1 to 2. At least numerous comments at
    > > > github.com/lwfinger/rtlwifi_new claimed they needed to make that change.
    > > >
    > > > Mhy recommended method is to verify the wifi device name with "iw dev". Then
    > > > using that device
    > > >
    > > > sudo iw dev <dev_name> scan | egrep "SSID|signal"
    > > >
    > > 
    > > I have confirmed that the performance regression is indeed tied to
    > > signal strength: on the good cases signal was between -16 and -8 dBm,
    > > whereas in bad cases signal was always between -50 to - 40 dBm. I've
    > > also switched to testing bandwidth in controlled LAN environment using
    > > iperf3, as suggested by Steve deRosier, with the DUT being the only
    > > machine connected to the 2.4 GHz radio and the machine running the
    > > iperf3 server connected via ethernet.
    > > 
    >
    > We have new experimental results in commit af8a41cccf8f46 ("rtlwifi: cleanup 
    > 8723be ant_sel definition"). You can use the above commit and do the same 
    > experiments (with ant_sel=0, 1 and 2) in your side, and then share your results.
    > Since performance is tied to signal strength, you can only share signal strength.
    >

    Please pay attention to cold reboot once ant_sel is changed.

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