On Thursday, July 1, 2021 at 10:46:50 AM UTC-4 ren...@ix.netcom.com wrote:
> If you are doing “anything” which such large objects - doesn’t that dwarf
> the time to increase the stack?
>
Yes, the unreachable code in the 2nd goroutine dwarts the stack grow time
much.
>
> On Jul 1, 2021, at 9:28 AM, tapi...@gmail.com <tapi...@gmail.com> wrote:
>
>
>
> I tried to find a way to initialize the size of the stack of a new created
> goroutine in advance to avoid several stack copies.
> Before this fix, the efficiencies of the two new goroutines are almost the
> same.
> After the fix, the second goroutine uses much less time than the first one.
>
> package main
>
> import "fmt"
> import "time"
>
> const N = 1024 * 1024
> var n byte = 123
>
> func f(v [N]byte, n int) {
> if n > 0 {
> f(v, n-1)
> }
> }
>
> func main() {
> var c = make(chan time.Duration, 1)
> go func() {
> start := time.Now()
> f([N]byte{}, 32)
> c <- time.Since(start)
> }()
> fmt.Println(<-c)
> go func() {
> start := time.Now()
> if n == 0 {
> var a, b, c, d, e, f, g [N*10]byte
> n = a[n] + b[n] + c[n] + d[n] + e[n] + f[n] + g[n]
> }
> f([N]byte{}, 32)
> c <- time.Since(start)
> }()
> fmt.Println(<-c)
> }
>
>
>
> On Thursday, July 1, 2021 at 2:23:45 AM UTC-4 axel.wa...@googlemail.com
> wrote:
>
>> Okay, *now* I get what you are trying to say. I agree that it seems
>> inefficient to call it more than once, which is why the code tries to
>> optimize for that. I don't know why that optimization doesn't trigger in
>> your case - you might want to try and investigate that. There might be a
>> good reason why it doesn't (for example, I'll note that your code might be
>> using the system stack, which, AIUI, is special).
>>
>> As always, if you are experiencing a real problem due to this, you might
>> want to open an issue.
>>
>> On Thu, Jul 1, 2021 at 3:04 AM tapi...@gmail.com <tapi...@gmail.com>
>> wrote:
>>
>>>
>>>
>>> On Wednesday, June 30, 2021 at 8:46:19 PM UTC-4
>>> axel.wa...@googlemail.com wrote:
>>>
>>>> On Thu, Jul 1, 2021 at 2:34 AM tapi...@gmail.com <tapi...@gmail.com>
>>>> wrote:
>>>>
>>>>>
>>>>>
>>>>> On Wednesday, June 30, 2021 at 11:56:45 AM UTC-4 Brian Candler wrote:
>>>>>
>>>>>> So I think what you're asking is, "under what scenario does the code
>>>>>> in L1066-1069
>>>>>> <https://github.com/golang/go/blob/d19a53338fa6272b4fe9c39d66812a79e1464cd2/src/runtime/stack.go#L1065-L1070>
>>>>>>
>>>>>> get run?" - is that right?
>>>>>
>>>>>
>>>>> Almost true.
>>>>>
>>>>> Whether or not it should run, growing the stack from 2048 to 512M in
>>>>> 18+ steps looks not right.
>>>>>
>>>>
>>>> Why? 2048 • 2^18 = 2^11 • 2^18 = 2^29 = 536870912.
>>>> Seems like exactly the expected result.
>>>>
>>>
>>> It looks each step calls copystack once.
>>> Isn't one step more efficient?
>>>
>>>
>>>>
>>>>
>>>>>
>>>>>
>>>>>>
>>>>>> On Wednesday, 30 June 2021 at 14:21:21 UTC+1 tapi...@gmail.com wrote:
>>>>>>
>>>>>>> Sorry, I post the wrong anchor. It is line 1068:
>>>>>>> https://github.com/golang/go/blob/d19a53338fa6272b4fe9c39d66812a79e1464cd2/src/runtime/stack.go#L1068
>>>>>>>
>>>>>>> On Wednesday, June 30, 2021 at 5:08:30 AM UTC-4 Brian Candler wrote:
>>>>>>>
>>>>>>>> On Wednesday, 30 June 2021 at 08:25:59 UTC+1 tapi...@gmail.com
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>>
>>>>>>>>> It looks this line
>>>>>>>>> https://github.com/golang/go/blob/master/src/runtime/stack.go#L1078
>>>>>>>>> never gets executed.
>>>>>>>>>
>>>>>>>>>
>>>>>>>> Can you quote the line you're referring to? Line numbers can shift
>>>>>>>> up and down as commits are made to the master branch. Right now, L1078
>>>>>>>> is a
>>>>>>>> blank line.
>>>>>>>>
>>>>>>> --
>>>>>
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>>>>>
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>>>>> .
>>>>>
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>>>
>> --
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