awreece

# Comments in makefiles follow the same form as comments in bash.
# Makefiles need to be named "Makefile" or "makefile".

# In makefiles, variables are declared in the following manner (the entire
# string after the equals and up to but excluding the newline is the 
# content of the variable) 
# 
# Note: there are other ways to declare variables that are not explored in this 
# tutorial.
TARGET = my_cc

awreece

$ go build thingy
# thingy
src/thingy/main.go:6: imported and not used: "mypkg"
src/thingy/main.go:14: undefined: mypkg

awreece

// +build ignore

// malloc test for false sharing


package main

import (
	"flag"
	"runtime"

awreece

package main

import "http"

func main() {
    http.Handle("/", http.FileServer(http.Dir("/tmp")))
    http.ListenAndServe(":8080", nil)
}

awreece

$ hg blame runtime.c | grep runtime·rnd
 6707: runtime·rnd(uint32 n, uint32 m)
$ hg log -r 6707
changeset:   6707:629c065d3679
user:        Russ Cox <rsc@golang.org>
date:        Thu Nov 04 14:00:19 2010 -0400
summary:     runtime: ,s/[a-zA-Z0-9_]+/runtime·&/g, almost

awreece

package main                                                                    
                                                                                
import (                                                                        
        "fmt"                                                                   
)                                                                               
                                                                                
func main() {
        done := false                                                                   
        go func() {                                                             
                for !done {                                                           

awreece

$ ./malloctest --proc=2 --iters=100 --prof 2>out2.prof
$ go tool pprof malloctest out2.prof 
out2.prof: header size >= 2**16
go tool pprof: exit status 1

awreece

func ptr2uintptr(ptr []byte) uintptr {                                          
        return uintptr(unsafe.Pointer(ptr)) // cannot convert ptr (type []byte) to type unsafe.Pointer
                                     
        /*                                                                      
        if bp, e := strconv.ParseInt(fmt.Sprintf("%p", ptr), 0, 32); e != nil { 
                log.Fatal(e)                                                    
        } else {                                                                
                return uintptr(bp)                                              
        }                                                                       
        panic("unreachable")                                                    

awreece

areece@areece-laptop:~/coding/gomalloc$ ./malloccheck --checkcache=true --procs=1
Malloc check ran with 1 procs for 1000000 iters of size 16
	Cache line shared 0 (0.00%) times
	Cache was reused 993536 (99.35%) times
areece@areece-laptop:~/coding/gomalloc$ ./malloccheck --checkcache=true --procs=2
Malloc check ran with 2 procs for 1000000 iters of size 16
	Cache line shared 128186 (12.82%) times
	Cache was reused 859014 (85.90%) times
areece@areece-laptop:~/coding/gomalloc$ ./malloccheck --checkcache=true --procs=3
Malloc check ran with 3 procs for 1000000 iters of size 16

awreece

--- a/src/pkg/runtime/malloc.goc	Mon Apr 09 15:39:59 2012 -0400
+++ b/src/pkg/runtime/malloc.goc	Mon Apr 23 17:37:10 2012 -0400
@@ -25,7 +25,7 @@
 // Small objects are allocated from the per-thread cache's free lists.
 // Large objects (> 32 kB) are allocated straight from the heap.
 void*
-runtime·mallocgc(uintptr size, uint32 flag, int32 dogc, int32 zeroed)
+INVALID_FUNC_DECLruntime·mallocgc(uintptr size, uint32 flag, int32 dogc, int32 zeroed)
 {
 	int32 sizeclass, rate;