netdev - RE: RTL8723BE performance regression

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Date:   Wed, 2 May 2018 05:44:38 +0000
From:   Pkshih <pkshih@...ltek.com>
To:     João Paulo Rechi Vita <jprvita@...il.com>,
        "Larry Finger" <Larry.Finger@...inger.net>
CC:     Steve deRosier <derosier@...il.com>,
        莊彥宣 <yhchuang@...ltek.com>,
        Birming Chiu <birming@...ltek.com>,
        Shaofu <shaofu@...ltek.com>,
        Steven Ting <steventing@...ltek.com>,
        Chaoming_Li <chaoming_li@...lsil.com.cn>,
        Kalle Valo <kvalo@...eaurora.org>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Daniel Drake <drake@...lessm.com>,
        João Paulo Rechi Vita <jprvita@...lessm.com>,
        "linux@...lessm.com" <linux@...lessm.com>
Subject: RE: RTL8723BE performance regression



> -----Original Message-----
> From: João Paulo Rechi Vita [mailto:jprvita@...il.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@...lessm.com
> Subject: Re: RTL8723BE performance regression
> 
> On Tue, Apr 3, 2018 at 7:51 PM, Larry Finger <Larry.Finger@...inger.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@...inger.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.

Regards
PK