runtime: go1.5 works slower than go1.4?

[awesomeleo]

I have built and installed go1.5 from source, and use it to build my project. But i find it works slower than
built from go1.4.2. the performance is only 60% as it built from go1.4.2. My project uses a lot of goroutines to call rocksdb which is implmented by c.
I have heared of go1.5 will work faster than go1.4, but what i see is not as that at current time. Will go1.5 work faster in release version?

[bradfitz]

Some parts are faster and some parts are slower. On average, it's faster overall.

Do you have a specific repro case?

[awesomeleo]

Dear bradfitz,
Thanks for your reply. I have made a test program, test1 works faster in go1.5, but test2 works slower in go1.5. I think maybe goroutine works slow in go1.5.

package main

// #include <stdio.h>
// #include <stdlib.h>
/*
void process(char *str) {
    //printf("%s\n", str);
    if(str!=NULL)
    {
        strstr(str,"Hello");
        strstr(str,"Cgo");
    }
}
*/
import "C"
import "unsafe"
import (
    "fmt"
    "time"
)

func test1() {
    s := "Hello Cgo"
    cs := C.CString(s)
    C.process(cs)
    C.free(unsafe.Pointer(cs))
}

func test2(done chan int) {
    s := "Hello Cgo"
    cs := C.CString(s)
    C.process(cs)
    C.free(unsafe.Pointer(cs))
    done <- 1
}
func main() {

    //test1
    count := 1000000
    t1 := time.Now()    
    for i := 0; i < count; i++ {
        test1()
    }
    t2 := time.Since(t1)
    fmt.Println("test1 time used:", t2)




    //test2
    count = 1000000
    t1 = time.Now()
    done := make(chan int)
    for i := 0; i < count; i++ {
        go test2(done)
    }

    for {
        <-done
        count = count - 1
        if count == 0 {
            break
        }
    }
    t2 = time.Since(t1)
    fmt.Println("time used:", t2)
}

[bradfitz]

Try with GOMAXPROCS=1. The default in Go 1.5 will be that GOMAXPROCS=NumCPU

[bradfitz]

I suspect this might just be a dup of #9704

Let's move this to the golang-nuts@ mailing list until a specific bug is identified.