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goroutine.md

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Goroutine

a function that is running concurrently.

Go program has at least one goroutine: main goroutine

When the goroutine has become blocked, goroutines are preemptable.

closure

Wikipedia: Closure

a technique for implementing lexically scoped name binding in a language with first-class functions.

Source Code

src/runtime/proc.go

Example

goroutine

Results:

Start
  3. Welcome
   4. hello (before Wait)
   4. welcome (after Wait)
1. Hello
    5. good day
    5. good day
    5. good day
     6. good day
     6. hello
     6. greetings
End
 2. Hi

Memory of a goroutine

Result:

2.583kb

Benchmark Context Switch

Use Linux or Virtual Machine

Install Packages

sudo apt install -y perf-tools-unstable linux-tools-5.4.0-65-generic linux-cloud-tools-5.4.0-65-generic linux-tools-generic linux-cloud-tools-generic

Benchmark thread

Measures the time it takes to send and receive a message on a thread:

taskset -c 0 perf bench sched pipe -T
# Running 'sched/pipe' benchmark:
# Executed 1000000 pipe operations between two threads

     Total time: 5.764 [sec]

       5.764207 usecs/op
         173484 ops/sec

Context Switch: Divide it by two

  • 5.764207 usecs/op / 2
  • 2.8821035 usecs/op
  • 2.8821035 μs per context switch

Benchmark goroutine

On macOS:

go test -bench=. -cpu=1 benchmark_test.go

goos: darwin
goarch: amd64
cpu: Intel(R) Core(TM) i7-7820HQ CPU @ 2.90GHz
BenchmarkContextSwitch   6457441               175.2 ns/op
PASS
ok      command-line-arguments  1.328s

On Linux VM:

cd /src/features/goroutine
go test -bench=. -cpu=1 benchmark_test.go

goos: linux
goarch: amd64
cpu: Intel(R) Core(TM) i7-7820HQ CPU @ 2.90GHz
BenchmarkContextSwitch   5725357               178.0 ns/op
PASS
ok      command-line-arguments  1.239s

Context Switch:

  • 175.2 ns/op ~ 178.0 ns/op
  • 0.175 μs per context switch