bytes.Clone for slice copying #96

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opened 2023-03-08 23:30:50 +00:00 by snegurochka · 2 comments

snegurochka commented

2023-03-08 23:30:50 +00:00

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Original issue: https://github.com/nspcc-dev/neofs-node/issues/2251

Go 1.20 finally brought to us a killer feature --- bytes.Clone library function that can... copy byte slices! We can finally replace slice.Copy (but not a `slice.CopyReverse, ha-ha) with something standard.

Original issue: https://github.com/nspcc-dev/neofs-node/issues/2251 Go 1.20 finally brought to us a killer feature --- bytes.Clone library function that can... copy byte slices! We can finally replace `slice.Copy` (but not a `slice.CopyReverse, ha-ha) with something standard.

fyrchik added the

label 2023-05-04 06:46:28 +00:00

fyrchik added this to the vNext milestone 2023-05-18 08:42:33 +00:00

fyrchik modified the milestone from vNext to v0.37.0

2023-08-08 19:11:10 +00:00

aarifullin self-assigned this 2023-08-10 11:46:18 +00:00

aarifullin commented

2023-08-10 14:05:25 +00:00

Collaborator

slice.Copy from github.com/nspcc-dev/neo-go/pkg/util/slice is defined like that:

// Copy copies the byte slice into new slice (make/copy).
func Copy(b []byte) []byte {
	d := make([]byte, len(b))
	copy(d, b)
	return d
}

while bytes.Clone is

// Clone returns a copy of b[:len(b)].
// The result may have additional unused capacity.
// Clone(nil) returns nil.
func Clone(b []byte) []byte {
	if b == nil {
		return nil
	}
	return append([]byte{}, b...)
}

So, Clone does not use preallocated memory that may lead to extra memory usage:

// The result may have additional unused capacity.

I suppose this may break heuristics for GOMEMLIMIT that's used by GC and so on

WDYT?

`slice.Copy` from `github.com/nspcc-dev/neo-go/pkg/util/slice` is defined like that: ```golang // Copy copies the byte slice into new slice (make/copy). func Copy(b []byte) []byte { d := make([]byte, len(b)) copy(d, b) return d } ``` while `bytes.Clone` is ```golang // Clone returns a copy of b[:len(b)]. // The result may have additional unused capacity. // Clone(nil) returns nil. func Clone(b []byte) []byte { if b == nil { return nil } return append([]byte{}, b...) } ``` So, `Clone` does not use preallocated memory that may lead to extra memory usage: ``` // The result may have additional unused capacity. ``` I suppose this may break heuristics for `GOMEMLIMIT` that's used by GC and so on WDYT?

aarifullin added the

discussion

label 2023-08-10 14:06:16 +00:00

aarifullin removed their assignment 2023-08-10 14:09:16 +00:00

fyrchik modified the milestone from v0.37.0 to v0.38.0

2023-08-29 09:12:49 +00:00