Low performance with Qemu's `pi2` and `pi3` machines

[carlosperate]

Compared with versatilepb + dhruvvyas90/qemu-rpi-kernel.

The total values are not important in this case, as these are for comparison against each other. All done on the same machine with the same internet connection, docker on x86 mac (so the container itself is running inside a linux vm):

	RAM	speedtest download	speedtest upload	cpu test single thread	cpu test 4 threads	disk write
bare docker container	8 GB	189.43 Mbit/s	77.49 Mbit/s	10 s	10 s	0.5 s
qemu versatilepb	256 MB	3.33 Mbit/s	6.84 Mbit/s	13 s	12 s	18 s
qemu pi2	1 GB	0.67 Mbit/s	0.62 Mbit/s	15 s	6 s	539 s
qemu pi3	1 GB	0.55 Mbit/s	0.72 Mbit/s	26 s	10 s	520 s

Speedtest: speedtest-cli --secure cpu single thread: sysbench --num-threads=1 --validate=on --test=cpu --cpu-max-prime=1000 run cpu 4 threads: sysbench --num-threads=4 --validate=on --test=cpu --cpu-max-prime=1000 run disk write: dd if=/dev/zero of=~/test.tmp bs=1M count=256 conv=fsync https://github.com/carlosperate/docker-qemu-rpi-os/blob/37ac36b820cf98f1da1acf61d1ffc27fcf1de978/benchmark-vm.py#L96-L118

[carlosperate]

Been looking into this and there are a few things to take in consideration.

• The original dockerpi project did not accurately emulate a Raspberry Pi 1, it had the commonly used versatilepb qemu machine configuration
  • https://www.qemu.org/docs/master/system/arm/versatile.html
  • The kernel and device tree used from dhruvvyas90/qemu-rpi-kernel has been built for this machine type
  • Probably okay for most people, but it's more like the Pi OS userspace running on top of a custom kernel and virtualised board
  • The 256 MB of RAM are a limitation that cannot be increased
• The Raspberry Pi 2 and 3 modes do use the qemu raspi machine types, and the kernel and device tree that come with the Pi OS images
  • https://www.qemu.org/docs/master/system/arm/raspi.html
  • However as shown above, the performance is quite low
• Similarly to the Raspberry Pi 1 versatilepb machine, the virt machine type can be used with a custom kernel, but more RAM
  • https://www.qemu.org/docs/master/system/arm/virt.html
  • Has a built the kernel in the Docker image as well

Added in commit: 49c922b8b9e30984767105cd8b9be960732ae095

	RAM	speedtest download	speedtest upload	cpu test single thread	cpu test 4 threads	disk write
qemu versatilepb	256 MB	3.33 Mbit/s	6.84 Mbit/s	13 s	12 s	18 s
qemu virt	1 GB	10.31 Mbit/s	10.75 Mbit/s	10 s	4 s	14 s