A simple tool that recreates functionality of elr-hw using Go. The tool also gives some insight into the performance of Go's scheduler and garbage collector. In our case, we've written this code to compare how Go's runtime fares when compared to Erlang. As such it may be treated as a benchmark of sorts, however make sure to take the results with a grain of salt.
The idea is to measure how the system behaves when a large number of processes is spawned. The do this the benchmark will create a couple of chains, each consisting of processes. In each chain, the processes will pass around a token from one to another and once a complete revolution/cycle is complete, the state of assigned LED/GPIO will be triggered.
In order to map the concepts from Erlang into Go, a goroutine is used
as a process and the token is passed over channels. The chain is
implemented inside src/chain/chain.go. To limit the effect of
spawning a large number of goroutines on the performance, we first
call chain.Spawn(), wait a little bit, and then call chain.Start()
to inject the token, thus starting the sequence.
Measurements are done on a tiny Linux system such as Raspberry Pi. A breadboard with LEDs is connected to GPIO pins of the board. The benchmark is expected to toggle the state of LEDs when running. For accurate timing measurements, connect a logical state analyzer to the GPIO to record a trace.
To build blinktest for Raspberry Pi run the following command:
GOARCH=arm GOARM=6 GOPATH=$PWD go build -v blinktest
Make sure to set GOARM appropriately when building for other ARM
based boards.
Before running on an embedded system make sure to adjust the GPIO/LED
mappings in src/blinktest/blinktest.go. The GPIOs are accessed via
/sys/class/gpio interface. In practice LEDs are not necessary,
however they provide a nice visual feedback.
The benchmark uses 4 GPIO pins: 4, 17, 27, 22.
Make sure to set GOARM=7 when building. GPIO pins on P8 header: 67
(P8.08), 68 (P8.10), 44 (P8.12), 24 (P8.14).
The GPIO pins can be assigned multiple functions, you need to
configure them into GPIO mode before running the benchmark. This can
be done by running a config-pin helper tool like this:
for p in P8.08 P8.10 P8.12 P8.14; do config-pin $p gpio; done
Make sure to set GOARM=7 when building. GPIO pins on GPIO-3 header:
35 (PB3), 37 (PB5), 39 (PB7), 40 (PB10).