gorout.go

package main

import (
    "time"
    "fmt"
    "runtime"
)

const NROUTINES = 1000000

func countThis(c chan int) {
    c <- 1
}

func main() {
    count_chan := make(chan int)

    spawnTime := time.Now()
    for i := 0; i < NROUTINES; i++ {
        go countThis(count_chan)
    }
    spawnDelta := time.Now().Sub(spawnTime)

    var m runtime.MemStats
    runtime.ReadMemStats(&m)
    fmt.Printf("Used memory after creating %v blocked goroutines:\n\tAllocs: %v bytes\n\tHeapAlloc: %v bytes\n\tSys mem: %v bytes\n\tNumGC: %v\n\n", NROUTINES, m.Alloc, m.HeapAlloc, m.Sys, m.NumGC)

    readTime := time.Now()
    total := 0
    for i := 0; i < NROUTINES; i++ {
        total += <-count_chan
    }
    close(count_chan)
    readDelta := time.Now().Sub(readTime)

    fmt.Printf("After running %v goroutines got %v as result\n", NROUTINES, total)
    fmt.Printf("Spawn time: %v; read from channel time: %v\n\n", spawnDelta, readDelta)

	fmt.Printf("Remaining goroutines: %v\n", runtime.NumGoroutine())
	time.Sleep(100 * time.Millisecond)
	fmt.Printf("Remaining goroutines after sleep: %v\n", runtime.NumGoroutine())

    runtime.GC()

    runtime.ReadMemStats(&m)
    fmt.Printf("Used memory after freeing %v blocked goroutines:\n\tAllocs: %v bytes\n\tHeapAlloc: %v bytes\n\tSys mem: %v bytes\n\tNumGC: %v\n\n", NROUTINES, m.Alloc, m.HeapAlloc, m.Sys, m.NumGC)
}

output_1.1.2.txt

λ go run main.go
Used memory after creating 1000000 blocked goroutines:
	Allocs: 264672024 bytes
	HeapAlloc: 264672024 bytes
	Sys mem: 4715580600 bytes
	NumGC: 2

After running 1000000 goroutines got 1000000 as result

Remaining goroutines: 1000001
Remaining goroutines after sleep: 3
Used memory after freeing 1000000 blocked goroutines:
	Allocs: 264724712 bytes
	HeapAlloc: 264724712 bytes
	Sys mem: 4715580600 bytes
	NumGC: 3

λ go version
go version go1.1.2 darwin/amd64

output_tip.txt

λ /Users/alco/Documents/git/go/bin/go run main.go
Used memory after creating 1000000 blocked goroutines:
	Allocs: 296576264 bytes
	HeapAlloc: 296576264 bytes
	Sys mem: 8583142648 bytes
	NumGC: 3

After running 1000000 goroutines got 1000000 as result

Remaining goroutines: 873972
Remaining goroutines after sleep: 3
Used memory after freeing 1000000 blocked goroutines:
	Allocs: 296576664 bytes
	HeapAlloc: 296576664 bytes
	Sys mem: 8584191224 bytes
	NumGC: 4

λ /Users/alco/Documents/git/go/bin/go version    
go version devel +7bc58b0d9de0 Wed Oct 09 08:37:06 2013 -0400 darwin/amd64