Re: TCP data throughput for BCM43362

["Jörg Krause" <joerg.krause@embedded.rocks>]

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On Mi, 2016-08-24 at 20:35 +0200, Arend Van Spriel wrote:
> On 22-8-2016 15:37, Jörg Krause wrote:
> > 
> > Hi all,
> > 
> > I am back from vacation and I'd like to do more investigations
> > about
> > this issue. Please see my comments below...
> > 
> > On Sun, 2016-08-07 at 13:41 +0200, Arend van Spriel wrote:
> > > 
> > > On 06-08-16 16:12, Jörg Krause wrote:
> > > > 
> > > > 
> > > > Hi all,
> > > 
> > > A bit weird email format making it a bit hard to determine where
> > > your
> > > last reply starts...
> > > 
> > > > 
> > > > 
> > > > On Fr, 2016-08-05 at 17:56 -0700, Franky Lin wrote:
> > > > 
> > > > On Fri, Aug 5, 2016 at 2:29 PM, Jörg Krause <joerg.krause@embed
> > > > ded.
> > > > ro
> > > > cks>
> > > > wrote:
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > > Am 5. August 2016 23:01:10 MESZ, schrieb Arend Van Spriel <
> > > > arend.vanspriel@broadcom.com>:
> > > > 
> > > > 
> > > > Op 5 aug. 2016 22:46 schreef "Jörg Krause"
> > > > <joerg.krause@embedded.rocks>:
> > > > 
> > > > 
> > > > 
> > > > Hi,
> > > > 
> > > > I'm using a custom ARM board with an BCM43362 wifi chip from
> > > > 
> > > > Broadcom.
> > > > 
> > > > 
> > > > The wifi chip is attached via SDIO to the controller with a
> > > > clock of
> > > > 48MHz. Linux kernel version is 4.7.
> > > > 
> > > > When measuring the network bandwidth with iperf3 I get a
> > > > bandwith of
> > > > only around 5 Mbps. I found a similar thread at the Broadcom
> > > > 
> > > > community
> > > > 
> > > > 
> > > > [1] where the test was done with a M4 CPU + BCM43362 and an
> > > > average
> > > > result of 3.3 Mbps.
> > > > 
> > > > Interestingly, a BCM43362 Wi-Fi Dev Kit [2] notes a TCP data
> > > > 
> > > > throughput
> > > > 
> > > > 
> > > > greater than 20 Mbps.
> > > > 
> > > > Why is the throughput I measured much lower? Note that I
> > > > measured
> > > > several times with almost no neighbor devices or networks.
> > > > 
> > > > This is a test sample measured with iperf3:
> > > > 
> > > >     $ iperf3 -c 192.168.2.1 -i 1 -t 10
> > > >     Connecting to host 192.168.2.1, port 5201
> > > >     [  4] local 192.168.2.155 port 36442 connected to
> > > > 192.168.2.1
> > > > 
> > > > port
> > > > 
> > > > 
> > > >     5201
> > > >     [ ID]
> > > > Interval           Transfer     Bandwidth       Retr  Cwnd
> > > >     [  4]   0.00-1.00   sec   615 KBytes  5.04
> > > > Mbits/sec    0   56.6
> > > >     KBytes
> > > >     [  4]   1.00-2.00   sec   622 KBytes  5.10
> > > > Mbits/sec    0   84.8
> > > >     KBytes
> > > >     [  4]   2.00-3.00   sec   625 KBytes  5.12
> > > > Mbits/sec    0    113
> > > >     KBytes
> > > >     [  4]   3.00-4.00   sec   571 KBytes  4.68
> > > > Mbits/sec    0    140
> > > >     KBytes
> > > >     [  4]   4.00-5.00   sec   594 KBytes  4.87
> > > > Mbits/sec    0    167
> > > >     KBytes
> > > >     [  4]   5.00-6.00   sec   628 KBytes  5.14
> > > > Mbits/sec    0    195
> > > >     KBytes
> > > >     [  4]   6.00-7.00   sec   619 KBytes  5.07
> > > > Mbits/sec    0    202
> > > >     KBytes
> > > >     [  4]   7.00-8.00   sec   608 KBytes  4.98
> > > > Mbits/sec    0    202
> > > >     KBytes
> > > >     [  4]   8.00-9.00   sec   602 KBytes  4.93
> > > > Mbits/sec    0    202
> > > >     KBytes
> > > >     [  4]   9.00-10.00  sec   537 KBytes  4.40
> > > > Mbits/sec    0    202
> > > >     KBytes
> > > >     - - - - - - - - - - - - - - - - - - - - - - - - -
> > > >     [ ID] Interval           Transfer     Bandwidth       Retr
> > > >     [  4]   0.00-10.00  sec  5.88 MBytes  4.93
> > > >     Mbits/sec    0             sender
> > > >     [  4]   0.00-10.00  sec  5.68 MBytes  4.76
> > > >     Mbits/sec                  receiver
> > > > 
> > > > 
> > > > Not overly familiar with iperf3. Do these lines mean you are
> > > > doing
> > > > bidirectional test, ie. upstream and downstream at the same
> > > > time.
> > > > Another
> > > > thing affecting tput could be power-save.
> > > > 
> > > > 
> > > > No, iperf3 does not support bidrectional test. Power-save is
> > > > turned
> > > > off.
> > > > 
> > > > What does iw link say?
> > > > 
> > > 
> > > but I guess it starts here!
> > > 
> > > > 
> > > > 
> > > > I compared the results with a Cubietruck I have:
> > > > 
> > > > # iperf3 -s
> > > > -----------------------------------------------------------
> > > > Server listening on 5201
> > > > -----------------------------------------------------------
> > > > Accepted connection from 192.168.178.46, port 42906
> > > > [  5] local 192.168.178.38 port 5201 connected to
> > > > 192.168.178.46
> > > > port
> > > > 42908
> > > > [ ID] Interval           Transfer     Bandwidth
> > > > [  5]   0.00-1.00   sec  2.29 MBytes  19.2
> > > > Mbits/sec                  
> > > > [  5]   1.00-2.00   sec  2.21 MBytes  18.5
> > > > Mbits/sec                  
> > > > [  5]   2.00-3.00   sec  2.17 MBytes  18.2
> > > > Mbits/sec                  
> > > > [  5]   3.00-4.00   sec  2.09 MBytes  17.6
> > > > Mbits/sec                  
> > > > [  5]   4.00-5.00   sec  2.20 MBytes  18.5
> > > > Mbits/sec                  
> > > > [  5]   5.00-6.00   sec  2.64 MBytes  22.1
> > > > Mbits/sec                  
> > > > [  5]   6.00-7.00   sec  2.67 MBytes  22.4
> > > > Mbits/sec                  
> > > > [  5]   7.00-8.00   sec  2.62 MBytes  22.0
> > > > Mbits/sec                  
> > > > [  5]   8.00-9.00   sec  2.35 MBytes  19.8
> > > > Mbits/sec                  
> > > > [  5]   9.00-10.00  sec  2.30 MBytes  19.3
> > > > Mbits/sec                  
> > > > [  5]  10.00-10.03  sec  83.4 KBytes  23.5
> > > > Mbits/sec                  
> > > > - - - - - - - - - - - - - - - - - - - - - - - - -
> > > > [ ID] Interval           Transfer     Bandwidth       Retr
> > > > [  5]   0.00-10.03  sec  23.9 MBytes  20.0
> > > > Mbits/sec    0             sender
> > > > [  5]   0.00-10.03  sec  23.6 MBytes  19.8
> > > > Mbits/sec                  receiver
> > > > 
> > > > # iw dev wlan0 link
> > > > Connected to xx:xx:xx:xx:xx (on wlan0)
> > > > 	SSID: xxx
> > > > 	freq: 2437
> > > > 	tx bitrate: 65.0 MBit/s
> > > > 
> > > > 	bss flags:	short-preamble short-slot-time
> > > > 	dtim period:	1
> > > > 	beacon int:	100
> > > 
> > > Too bad RSSI is not in the output above. That may be due to a
> > > regression
> > > in our driver which has been fixed by commit 94abd778a7bb
> > > ("brcmfmac:
> > > add fallback for devices that do not report per-chain values").
> > > However,
> > > the tx bitrate seems within the same range as the other platform.
> > > 
> > > > 
> > > > 
> > > > The Cubietruck works also with the brcmfmac driver.
> > > > 
> > > > May it depend on the NVRAM file?
> > > 
> > > Not sure. Can you tell me a bit more about the custom ARM board.
> > > Does
> > > it
> > > use the same wifi module as Cubietruck, ie. the AMPAK AP6210? If
> > > you
> > > can
> > > make a wireshark sniff we can check the actual bitrate and medium
> > > density in terms of packets. Another thing to look at is the SDIO
> > > host
> > > controller. In brcmf_sdiod_sgtable_alloc() some key values are
> > > used
> > > from
> > > the host controller. It only logs the number of entries of the
> > > scatter-gather table, but could you add the other values in this
> > > function that are used to determine the number of entries.
> > 
> > My board uses the BCM43362 chip solely (no Bluetooth) attached to
> > the
> > SDIO interface of a NXP i.MX28 processor.
> > 
> > I added some additional printk() to brcmf_sdiod_sgtable_alloc().
> > These
> > are the values printed after modprobe brcmfmac:
> > 
> > [    8.926657] sg_support=1
> > [    8.929440] max_blocks=511
> > [    8.932213] max_request_size=261632
> > [    8.935741] max_segment_count=52
> > [    8.939005] max_segment_size=65280
> > [    8.946095] nents=35
> 
> Thanks. That looks good.
> 
> > 
> > Additionally I attached a xz compresses wireshark sniff while
> > running
> > iper3 between the BCM43362 running as in AP mode with iperf3 as a
> > server and a PC in station mode running iperf3 as a client.
> 
> Looking at the sniff it seems you captured on the ethernet side. That
> does not give me any 802.11 specific info. Can you make a wireless
> capture preferably without encryption.

You,re right! Sorry for this mistake. I did a re-capture on the
wireless side now.

Best regards
Jörg Krause

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