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--- searchwing-pi-datarate [2019/11/27 15:24]
beckmanf [iperf measurements via WLAN]
+++ searchwing-pi-datarate [2021/11/18 15:08] (current)
wf68spef [pi4 config]
@@ Line 1: / Line 1: @@
-===== Raspberry Pi data transfer rate test =====
+===== Raspberry Pi Zero data transfer rate test =====
 The Raspberry Pi stores the images which are collected during flight. After the plane landed, the images are retrieved from the Pi. The least impact with respect to water sealing would be a wireless transfer via Wifi or Bluetooth. For completeness I also test the transfer rate via USB configured as RNDIS network device. As a seperate topic I look into the transfer rate of the SD Card.
@@ Line 266: / Line 266: @@
 The CPU is fully loaded with the iperf process (80%) and the interrupt service (14%). The transfer rate is again 150 MBit/s.
+==== ssh transfer via usb ===
+I created 3 files with different size
+  * tf1mb - 1 MB
+  * tf3mb - 3 MB
+  * tf100mb - 100Mb
+The following example creates the file "tf3mb" with random content and a size of 3000000 bytes (3 MB).
+<code>
+pi@raspberrypi:~ $ dd if=/dev/urandom of=tf3mb bs=1000 count=3000
++0 records in
++0 records out
+3000000 bytes (3.0 MB, 2.9 MiB) copied, 0.272827 s, 11.0 MB/s
+pi@raspberrypi:
+</code>
+The I copied the file from the Pi to the Mac via scp.
+<code>
+Fredo:~ fritz$ scp pi@192.168.2.2:~/tf1mb .
+pi@192.168.2.2's password:
+tf1mb                                         100%  977KB   4.8MB/s   00:00
+Fredo:~ fritz$ scp pi@192.168.2.2:~/tf3mb .
+pi@192.168.2.2's password:
+tf3mb                                         100% 2930KB   5.1MB/s   00:00
+Fredo:~ fritz$ scp pi@192.168.2.2:~/tf100mb .
+pi@192.168.2.2's password:
+tf100mb                                       100%   95MB   5.2MB/s   00:18
+Fredo:~ fritz$
+</code>
+The reported rate is 5.2 MB/s. The transfer time as reported by scp -v is shown in the following table together with the effective rate.
+^File     ^ Size             ^ Time         ^ Rate       ^
+|tf1mb    | 1000000 Bytes    | 0.6 s        | 13 MBit/s  |
+|tf3mb    | 3000000 Bytes    | 0.9 s        | 27 MBit/s  |
+|tf100mb  | 100000000 Bytes  | 18.8 s       | 42 MBit/s  |
+The transfer rate depends on the file size. Compared to the rate of 150 MBit/s as reported by iperf, there is substantial mismatch. The CPU load during the transfer as shown by top is
+<code>
+top - 14:55:32 up  2:00,  3 users,  load average: 0.52, 0.15, 0.13
+Tasks:  82 total,   3 running,  79 sleeping,   0 stopped,   0 zombie
+%Cpu(s): 53.3 us, 35.9 sy,  0.0 ni,  0.0 id,  0.0 wa,  0.0 hi, 10.8 si,  0.0 st
+MiB Mem :    432.7 total,    217.3 free,     41.1 used,    174.3 buff/cache
+MiB Swap:    100.0 total,    100.0 free,      0.0 used.    339.5 avail Mem
+  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
+pi        20   0   12320   4244   3320 R  89.2   1.0   0:13.13 sshd
+pi        20   0    6648   1828   1724 S   7.5   0.4   0:01.12 scp
+root      20   0   27640   1380   1240 S   1.3   0.3   0:19.77 rngd
+root      20   0       0      0      0 R   1.0   0.0   2:32.59 ksoftirqd/0
+pi        20   0   10168   2848   2428 R   1.0   0.6   0:00.71 top
+root     -51   0       0      0      0 S   0.3   0.0   1:25.49 irq/86-mmc1
+root      20   0   32532   7884   6384 S   0.0   1.8   0:05.07 systemd
+</code>
+The CPU is fully loaded. 90% of the time is spent in the ssh daemon. This is probably due to the encryption of ssh. The rate is limited by CPU load. For short files the initial transactions probably limit the rate.
+==== http transfer via USB ====
+I installed the lighttpd web server on the Raspberry Pi and tested the file transfer via wget.
+<code>
+Fredo:~ fritz$ wget 192.168.2.2/tf100mb
+--2019-11-27 16:52:57--  http://192.168.2.2/tf100mb
+Verbindungsaufbau zu 192.168.2.2:80 … verbunden.
+HTTP-Anforderung gesendet, auf Antwort wird gewartet … 200 OK
+Länge: 100000000 (95M) [application/octet-stream]
+Wird in »tf100mb.2« gespeichert.
+tf100mb.2                        100%[========================================================>]  95,37M  18,6MB/s    in 5,2s
+-11-27 16:53:02 (18,5 MB/s) - »tf100mb.2« gespeichert [100000000/100000000]
+Fredo:~ fritz$
+</code>
+It takes 5.2s to transfer the 100MB file. That corresponds to a speed of 153 Mbit/s. The full usb speed according to iperf is used. The transfer times for the 1MB file are 0.06s and for the 3MB file 0.2s.
 ==== iperf measurements via WLAN ====
@@ Line 339: / Line 421: @@
 The iperf client transfer results in a CPU load of 50%. The iperf process consumes only 3%, while most of the cpu power goes to the interrupt handling of the wlan driver.
+==== ssh transfer with wlan ====
+The ssh results for the wifi transfer are
+<code>
+Fredo:~ fritz$ scp pi@192.168.178.84:~/tf1mb .
+pi@192.168.178.84's password:
+tf1mb                                              100%  977KB   2.1MB/s   00:00
+Fredo:~ fritz$ scp pi@192.168.178.84:~/tf3mb .
+pi@192.168.178.84's password:
+tf3mb                                              100% 2930KB   2.3MB/s   00:01
+Fredo:~ fritz$ scp pi@192.168.178.84:~/tf100mb .
+pi@192.168.178.84's password:
+tf100mb                                            100%   95MB   1.6MB/s   00:58
+Fredo:~ fritz$ scp pi@192.168.178.84:~/tf100mb .
+pi@192.168.178.84's password:
+tf100mb                                            100%   95MB   1.8MB/s   00:54
+Fredo:~ fritz$ scp pi@192.168.178.84:~/tf100mb .
+pi@192.168.178.84's password:
+tf100mb                                            100%   95MB   1.8MB/s   00:53
+Fredo:~ fritz$ scp pi@192.168.178.84:~/tf100mb .
+pi@192.168.178.84's password:
+tf100mb                                            100%   95MB   1.7MB/s   00:55
+Fredo:~ fritz$ scp pi@192.168.178.84:~/tf100mb .
+pi@192.168.178.84's password:
+tf100mb                                            100%   95MB   1.9MB/s   00:51
+Fredo:~ fritz$ scp pi@192.168.178.84:~/tf1mb .
+pi@192.168.178.84's password:
+tf1mb                                              100%  977KB   1.8MB/s   00:00
+Fredo:~ fritz$ scp pi@192.168.178.84:~/tf3mb .
+pi@192.168.178.84's password:
+Permission denied, please try again.
+pi@192.168.178.84's password:
+tf3mb                                              100% 2930KB   2.0MB/s   00:01
+Fredo:~ fritz$
+</code>
+During the transfer of the 100 MByte file, the cpu load according to top is
+<code>
+top - 15:36:21 up 18 min,  1 user,  load average: 0.96, 0.86, 0.58
+Tasks:  76 total,   2 running,  74 sleeping,   0 stopped,   0 zombie
+%Cpu(s): 23.3 us, 39.5 sy,  0.0 ni,  3.9 id,  0.0 wa,  0.0 hi, 33.3 si,  0.0 st
+MiB Mem :    432.7 total,    222.8 free,     40.1 used,    169.7 buff/cache
+MiB Swap:    100.0 total,    100.0 free,      0.0 used.    341.3 avail Mem
+  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
+pi        20   0   15852   7740   3208 R  29.5   1.7   0:08.32 sshd
+root      20   0       0      0      0 D  29.2   0.0   0:50.23 kworker/u2:3++
+root     -51   0       0      0      0 D  28.8   0.0   1:20.66 irq/86-mmc1
+pi        20   0    6620   1760   1656 S   3.2   0.4   0:00.70 scp
+root      20   0       0      0      0 S   2.6   0.0   0:12.60 ksoftirqd/0
+pi        20   0   10172   2856   2432 R   1.0   0.6   0:08.43 top
+root      20   0   27640   1420   1292 S   0.6   0.3   0:01.62 rngd
+</code>
+The CPU is fully loaded and 30% are used for the ssh daemon and 60% are required for the wifi driver. It takes about 55s to transfer the 100 MB file. The rate is therefore around 14 MBit/s. The 1MB files take 0.8s (=10 MBit/s) and the 3MB file takes 2.5s (=10 MBit/s).
+==== http transfer time for wifi ====
+The results for the wget transfer time are 0.8s for the 1MB file, 1.1s for the 3MB file and 30s for teh 100MB file. However, these measurements were made at 19.00, i.e. there is quite some traffic on channel 1 now...
+The transfer times for the 100MB were 30s, 24s, 25s, 26s. This corresponds to a transfer rate of 30 MBit/s. Some times for the 1MB file were: 0.2 0.2 0.2 0.9 0.3 0.7 0.7 0.2 -> There is heavy congestion on channel 1.
+Based on the 0.2s for the 1 MB File, this translates to **5 MB/s = 40 MBit/s** rate for an undisturbed channel for a transfer via http. This is again exactly the achieved iperf rate as shown above.
+==== Julian tests ====
+  * WIFI Only datatransfer
+  * Router: FritzBox 7430 AW
+  * Placement: Pi Zero and Laptop placed 10cm above router.
+  * data ammount: 540 MByte
+  * ** Laptop and Raspberry Pi share the same Wifi channel => Each packet goes from Pi to AP and from AP to Laptop. => Congestion on the Wifi Channel. **
+=== wget ===
+  * time=213sek
+  * rate=2.53 Mbyte/sek
+  * cpuusage=70%
+=== ftp ===
+  * time=361sek
+  * rate=1.495 Mbyte/sek
+  * cpuusage=50-60%
 ==== Results ====
+  * The Laptop and the Pi should not be connected via a single 2.4 GHz access point as laptop and Pi share the same Wifi channel. This results in 50% throughput reduction (see Julians 2.5 MB/s for wget).
+  * The transfer rate via wget on an undisturbed 2.4 GHz wifi channel is **5 MB/s**. (Only Pi connected to AP, No other stations use this channel). This 40 MBit/s throughput on http level compares well to the maximum 65 MBit/s wifi data rate of the Pi Zero W.
+  * ssh transfer is limited by CPU load on the Pi for encryption and results in 1.8 MB/s for Wifi.
+  * Short Guard Interval setting could possibly increase the the raw wifi rate from 65 MBit/s to 72 MBit/s.
@@ Line 350: / Line 519: @@
+===== Pi4/CM4 data transfer rate test =====
+  * Fritzbox 7520
+  * CM4 5Ghz Wifi
+  * Laptop T14 via Gigabit Ethernet
+==== pi4 theoretical speed ====
+from https://forums.raspberrypi.com/viewtopic.php?t=291824&start=25#p1768600
+//Fri Nov 27, 2020 2:03 pm
+The WiFi chip is connected via a 4-bit SDIO link that typically runs at 41.7MHz giving an upper **limit on throughput of ~160Mbs**. In practise you won't get close to that because it is a simplex link (only one direction at a time) and there is overhead in each of the protocol and transport layers. Given that, 112Mbps sounds pretty good. Even though the throughput hasn't increased, being able to properly use the wide channels means that the channel (which is a shared medium) is occupied for a shorter time, leaving more time for other devices.
+//
+==== pi4 config ====
+<code>
+pi@testi:~ $ iw dev
+phy#0
+	Unnamed/non-netdev interface
+		wdev 0x2
+		addr de:a6:32:fe:85:b0
+		type P2P-device
+		txpower 31.00 dBm
+	Interface wlan0
+		ifindex 3
+		wdev 0x1
+		addr dc:a6:32:fe:85:b0
+		ssid DrMartinRouterKing
+		type managed
+		channel 64 (5320 MHz), width: 80 MHz, center1: 5290 MHz
+		txpower 31.00 dBm
+pi@testi:~ $ iwconfig wlan0
+wlan0     IEEE 802.11  ESSID:"XXXXXXXXXXXX"
+          Mode:Managed  Frequency:5.32 GHz  Access Point: 3C:A6:2F:CB:E0:7E
+          Bit Rate=433.3 Mb/s   Tx-Power=31 dBm
+          Retry short limit:7   RTS thr:off   Fragment thr:off
+          Power Management:on
+          Link Quality=70/70  Signal level=-29 dBm
+          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
+          Tx excessive retries:1  Invalid misc:0   Missed beacon:0
+</code>
+==== iperf measurements via WLAN ====
+=== Datatransfer Pi4 -> Laptop ===
+<code>
+➜  /tmp iperf3 -s
+-----------------------------------------------------------
+Server listening on 5201 (test #1)
+-----------------------------------------------------------
+Accepted connection from 192.168.178.29, port 54534
+[  5] local 192.168.178.20 port 5201 connected to 192.168.178.29 port 54536
+[ ID] Interval           Transfer     Bitrate
+[  5]   0.00-1.00   sec  9.14 MBytes  76.7 Mbits/sec
+[  5]   1.00-2.00   sec  10.8 MBytes  90.9 Mbits/sec
+[  5]   2.00-3.00   sec  10.9 MBytes  91.1 Mbits/sec
+[  5]   3.00-4.00   sec  10.8 MBytes  90.9 Mbits/sec
+[  5]   4.00-5.00   sec  10.9 MBytes  91.5 Mbits/sec
+[  5]   5.00-6.00   sec  10.3 MBytes  86.2 Mbits/sec
+[  5]   6.00-7.00   sec  9.21 MBytes  77.3 Mbits/sec
+[  5]   7.00-8.00   sec  10.9 MBytes  91.1 Mbits/sec
+[  5]   8.00-9.00   sec  10.8 MBytes  90.7 Mbits/sec
+[  5]   9.00-10.00  sec  10.9 MBytes  91.5 Mbits/sec
+[  5]  10.00-10.01  sec   103 KBytes  89.2 Mbits/sec
+- - - - - - - - - - - - - - - - - - - - - - - - -
+[ ID] Interval           Transfer     Bitrate
+[  5]   0.00-10.01  sec   105 MBytes  87.8 Mbits/sec                  receiver
+-----------------------------------------------------------
+Server listening on 5201 (test #2)
+-----------------------------------------------------------
+^Ciperf3: interrupt - the server has terminated
+</code>
+=== Datatransfer Pi4 <- Laptop ===
+<code>
+➜  /tmp iperf3 -c 192.168.178.29
+iperf3: error - unable to connect to server: Connection refused
+➜  /tmp iperf3 -c 192.168.178.29
+Connecting to host 192.168.178.29, port 5201
+[  5] local 192.168.178.20 port 40318 connected to 192.168.178.29 port 5201
+[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
+[  5]   0.00-1.00   sec  5.21 MBytes  43.7 Mbits/sec   24   24.0 KBytes
+[  5]   1.00-2.00   sec  4.57 MBytes  38.4 Mbits/sec   32   22.6 KBytes
+[  5]   2.00-3.00   sec  4.75 MBytes  39.8 Mbits/sec   35   38.2 KBytes
+[  5]   3.00-4.00   sec  5.11 MBytes  42.8 Mbits/sec   36   28.3 KBytes
+[  5]   4.00-5.00   sec  4.51 MBytes  37.9 Mbits/sec   24   31.1 KBytes
+[  5]   5.00-6.00   sec  5.11 MBytes  42.8 Mbits/sec   31   21.2 KBytes
+[  5]   6.00-7.00   sec  5.23 MBytes  43.8 Mbits/sec   23   35.4 KBytes
+[  5]   7.00-8.00   sec  5.46 MBytes  45.8 Mbits/sec   27   21.2 KBytes
+[  5]   8.00-9.00   sec  4.99 MBytes  41.8 Mbits/sec   20   35.4 KBytes
+[  5]   9.00-10.00  sec  4.63 MBytes  38.9 Mbits/sec   41   19.8 KBytes
+- - - - - - - - - - - - - - - - - - - - - - - - -
+[ ID] Interval           Transfer     Bitrate         Retr
+[  5]   0.00-10.00  sec  49.6 MBytes  41.6 Mbits/sec  293             sender
+[  5]   0.00-10.00  sec  49.3 MBytes  41.4 Mbits/sec                  receiver
+iperf Done.
+</code>