On Sun, Mar 1, 2020 at 5:56 AM Jason E. Aten <j.e.a...@gmail.com> wrote:
>
> escape analysis is eliminating the allocation in the simplification. in
> reality the slice is stored in a persistent struct.
Can you show us a complete example program? It's possible that the
allocation is getting attributed to the wrong line, or that the
expected line has been eliminated by the compiler. Thanks.
Ian
> On Sun, Mar 1, 2020 at 8:50 AM <so.peter...@gmail.com> wrote:
>>
>> Jason,
>>
>> Your example does not appear to support your claim.
>>
>> A benchmark:
>>
>> package main
>>
>> import (
>> "strconv"
>> "testing"
>> )
>>
>> type A struct {
>> B string
>> }
>>
>> func mycode(slice []A) {
>> slice = slice[1:]
>> }
>>
>> func BenchmarkMycode(b *testing.B) {
>> a := make([]A, 256)
>> for i := range a {
>> a[i].B = "B: " + strconv.Itoa(i*cap(a))
>> }
>> b.ResetTimer()
>> for N := 0; N < b.N; N++ {
>> mycode(a)
>> }
>> }
>>
>> Output:
>>
>> $ go version
>> go version go1.14 linux/amd64
>> $ go test mycode_test.go -bench=. -benchmem
>> BenchmarkMycode-4 1000000000 0.290 ns/op 0 B/op 0 allocs/op
>>
>> Peter
>>
>> On Saturday, February 29, 2020 at 6:53:18 PM UTC-5, Jason E. Aten wrote:
>>>
>>> Profiling suggests that reslicing to remove the first element of a slice is
>>> doing alot of allocation; for instance in mycode() below.
>>> This is surprising to me.... How could this be? is there anything I can do
>>> about it?
>>>
>>> e.g.
>>>
>>> type A struct{
>>> B string
>>> }
>>>
>>> func mycode(slice []A) {
>>> slice = slice[1:]
>>> }
>>
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>
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