[go-nuts] how dose netpollblock be awoken while sysmon sleep?
I have a test code like this:
func main() {
tcpAddress, err := net.ResolveTCPAddr("tcp", ":")
if err != nil {
fmt.Println(err)
}
listener, err := net.ListenTCP("tcp", tcpAddress)
c, e := listener.AcceptTCP()
if e != nil {
fmt.Println(e)
}
t := make([]byte, 0, 1000)
c.Read(t)
}
when the main function blocked on AcceptTCP(), the runtime.sysmon()
function will enter sleep soon which is because npidle equal to gomaxprocs.
and then a tcp connection comes, how dose acceptTCP be awoken? I couldn't
find a runtime.netpoll() been call anymore.
could some give some advise, effective tools, design document or debug
method to read golang's source code? I always want to debug some code in
runtime, but i
conn't find a effective way to do this now; I read these code so hard
without clearly understand the detail design .
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[go-nuts] Re: how dose netpollblock be awoken while sysmon sleep?
I got it. it because there is a blocking netpool in runtime.findrunable() function. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [go-nuts] how dose netpollblock been awaked while sysmon slepp?
thank you, i got it.
how did you debug the go runtime? use print or gcc, or some other tools?
Thank you for tolerate my grammatical mistakes again.
在 2017年4月20日星期四 UTC+8上午11:59:06，Ian Lance Taylor写道：
>
> On Wed, Apr 19, 2017 at 7:42 PM, 代君 >
> wrote:
> >
> > i have a test code like this:
> > func main() {
> > tcpAddress, err := net.ResolveTCPAddr("tcp", ":")
> > if err != nil {
> > fmt.Println(err)
> > }
> > listener, err := net.ListenTCP("tcp", tcpAddress)
> >
> > c, e := listener.AcceptTCP()
> > if e != nil {
> > fmt.Println(e)
> > }
> >
> > t := make([]byte, 0, 1000)
> > c.Read(t)
> > }
> > when the main function blocked on AcceptTCP(), the runtime.sysmon()
> > function will enter sleep soon which is because npidle equal to
> gomaxprocs.
> >
> > and then a tcp connect coming, how acceptTCP been waked? I couldn't find
> a
> > runtime.netpoll() been call anymore.
>
> In the findrunnable function, when a P tries to find a G to run, if
> there is nothing to run, but there are some goroutines waiting for
> network activity, then the P will block in a call to netpoll until
> something is ready.
>
> > could some give some advise, effective tools, design document or debug
> > method to read golang's source code? I always want to debug some code in
> > runtime, but i
> > conn't find a effective way to do this now; I read these code so hard
> > without clearly understand the detail design .
>
> For the scheduler you can read
>
> https://docs.google.com/document/d/1TTj4T2JO42uD5ID9e89oa0sLKhJYD0Y_kqxDv3I3XMw/view
>
> , although it is somewhat out of date.
>
> Ian
>
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[go-nuts] sigaction implementation on darwin
Where is the sigaction implementation on macos with purego?I only found the cgo implementation in runtime/sys_darwin.go. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/0ff0555a-e5c4-40d1-8bbd-c8b96a06e5a6n%40googlegroups.com.
[go-nuts] abort assembly code profile
I have some golang code like this:
```golang
type C [2]int
//go:noinline
func t1(a, b C) C {
var ret C
for i := 0; i < len(a); i++ {
ret[i] = a[i] + b[i]
}
return ret
}
//go:noinline
func t2(a, b C) C {
return t1(a, b)
}
```
and build with command: go build main.go
then i use objdump -d main to check the output assembly code, it like this:
```golang
000100086b40 <_main.t1>:
100086b40: fe 0f 1e f8 str x30, [sp, #-32]!
100086b44: fd 83 1f f8 sturx29, [sp, #-8]
100086b48: fd 23 00 d1 sub x29, sp, #8
100086b4c: ff ff 04 a9 stp xzr, xzr, [sp, #72]
100086b50: ff ff 00 a9 stp xzr, xzr, [sp, #8]
100086b54: 00 00 80 d2 mov x0, #0
100086b58: 09 00 00 14 b 0x100086b7c <_main.t1+0x3c>
100086b5c: e1 a3 00 91 add x1, sp, #40
100086b60: 22 78 60 f8 ldr x2, [x1, x0, lsl #3]
100086b64: e3 e3 00 91 add x3, sp, #56
100086b68: 64 78 60 f8 ldr x4, [x3, x0, lsl #3]
100086b6c: 42 00 04 8b add x2, x2, x4
100086b70: e4 23 00 91 add x4, sp, #8
100086b74: 82 78 20 f8 str x2, [x4, x0, lsl #3]
100086b78: 00 04 00 91 add x0, x0, #1
100086b7c: 1f 08 00 f1 cmp x0, #2
100086b80: eb fe ff 54 b.lt0x100086b5c <_main.t1+0x1c>
100086b84: e0 07 40 f9 ldr x0, [sp, #8]
100086b88: e1 0b 40 f9 ldr x1, [sp, #16]
100086b8c: e0 27 00 f9 str x0, [sp, #72]
100086b90: e1 2b 00 f9 str x1, [sp, #80]
100086b94: ff 83 00 91 add sp, sp, #32
100086b98: fd 23 00 d1 sub x29, sp, #8
100086b9c: c0 03 5f d6 ret
```
I think the above assembly code is not optimal。
1. the register value of x1,x3 can be compute out side of the loop.
2. store the result directly to [sp, #72], and [sp, #80], the temporary
data in [sp, #8] and [sp, #16] not necessary.
i want to know why the compiler couldn't do the optimize, or which command
cat go more optimized code.
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