We use a call to test -z together with go fmt because it doesn't output
a non-zero exit status (triggering CI test failure). However, we lose
useful debugging output from the go fmt call because test -z swallows
it. This adds very verbose formatting output to the CI test.
I had thought to set a buffer size of 2048, half the websocket package
default of 4096. But it turns out when you don't set a buffer size, the
websocket package reuses the HTTP server's read/write buffers, which
empirically already have a size of 2048.
$ go test -bench=BenchmarkUpgradeBufferSize -benchmem -benchtime=5s
BenchmarkUpgradeBufferSize/0-4 25669 234566 ns/op 32604 B/op 113 allocs/op
BenchmarkUpgradeBufferSize/128-4 24739 238283 ns/op 24325 B/op 117 allocs/op
BenchmarkUpgradeBufferSize/1024-4 25352 238885 ns/op 28087 B/op 116 allocs/op
BenchmarkUpgradeBufferSize/2048-4 22660 234890 ns/op 32444 B/op 116 allocs/op
BenchmarkUpgradeBufferSize/4096-4 25668 232591 ns/op 41672 B/op 116 allocs/op
BenchmarkUpgradeBufferSize/8192-4 24908 240755 ns/op 59103 B/op 116 allocs/op
Otherwise the buffers are re-allocated on every iteration, which is a
surprise to me. I thought the compiler would do this transformation
itself.
Now there is just one allocation per client←server read (one
messageReader) and two allocations per server←client read (one
messageReader and one messageWriter).
$ go test -bench=BenchmarkReadWrite -benchmem -benchtime=5s
BenchmarkReadWrite/c←s_150-4 481054 12849 ns/op 11.67 MB/s 8 B/op 1 allocs/op
BenchmarkReadWrite/s←c_150-4 421809 14095 ns/op 10.64 MB/s 56 B/op 2 allocs/op
BenchmarkReadWrite/c←s_3000-4 208564 28003 ns/op 107.13 MB/s 16 B/op 2 allocs/op
BenchmarkReadWrite/s←c_3000-4 186320 30576 ns/op 98.12 MB/s 112 B/op 4 allocs/op
In the client←server direction, this hits a fast path that avoids
allocating a messageWriter.
https://github.com/gorilla/websocket/blob/v1.5.0/conn.go#L760
Cuts the number of allocations in half in the client←server direction:
$ go test -bench=BenchmarkReadWrite -benchmem -benchtime=5s
BenchmarkReadWrite/c←s_150-4 597511 13358 ns/op 11.23 MB/s 33709 B/op 2 allocs/op
BenchmarkReadWrite/s←c_150-4 474176 13756 ns/op 10.90 MB/s 34968 B/op 4 allocs/op
BenchmarkReadWrite/c←s_3000-4 156488 36290 ns/op 82.67 MB/s 68673 B/op 5 allocs/op
BenchmarkReadWrite/s←c_3000-4 190897 34719 ns/op 86.41 MB/s 69730 B/op 8 allocs/op
