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encoding/binary: use an offset instead of slicing

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While running make.bash, over 5% of all pointer writes
come from encoding/binary doing struct reads.

This change replaces slicing during such reads with an offset.
This avoids updating the slice pointer with every
struct field read or write.

This has no impact when the write barrier is off.
Running the benchmarks with GOGC=1, however,
shows significant improvement:

name          old time/op    new time/op    delta
ReadStruct-8    13.2µs ± 6%    10.1µs ± 5%  -23.24%  (p=0.000 n=10+10)

name          old speed      new speed      delta
ReadStruct-8  5.69MB/s ± 6%  7.40MB/s ± 5%  +30.18%  (p=0.000 n=10+10)

Change-Id: I22904263196bfeddc38abe8989428e263aee5253
Reviewed-on: https://go-review.googlesource.com/98757
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Josh Bleecher Snyder 2018-03-05 07:40:14 -08:00
parent f7739c07c8
commit b85433975a
1 changed files with 29 additions and 27 deletions
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56
src/encoding/binary/binary.go
View File

@ -419,70 +419,71 @@ func sizeof(t reflect.Type) int {
}
type coder struct {
order ByteOrder
buf []byte
order ByteOrder
buf []byte
offset int
}
type decoder coder
type encoder coder
func (d *decoder) bool() bool {
x := d.buf[0]
d.buf = d.buf[1:]
x := d.buf[d.offset]
d.offset++
return x != 0
}
func (e *encoder) bool(x bool) {
if x {
e.buf[0] = 1
e.buf[e.offset] = 1
} else {
e.buf[0] = 0
e.buf[e.offset] = 0
}
e.buf = e.buf[1:]
e.offset++
}
func (d *decoder) uint8() uint8 {
x := d.buf[0]
d.buf = d.buf[1:]
x := d.buf[d.offset]
d.offset++
return x
}
func (e *encoder) uint8(x uint8) {
e.buf[0] = x
e.buf = e.buf[1:]
e.buf[e.offset] = x
e.offset++
}
func (d *decoder) uint16() uint16 {
x := d.order.Uint16(d.buf[0:2])
d.buf = d.buf[2:]
x := d.order.Uint16(d.buf[d.offset : d.offset+2])
d.offset += 2
return x
}
func (e *encoder) uint16(x uint16) {
e.order.PutUint16(e.buf[0:2], x)
e.buf = e.buf[2:]
e.order.PutUint16(e.buf[e.offset:e.offset+2], x)
e.offset += 2
}
func (d *decoder) uint32() uint32 {
x := d.order.Uint32(d.buf[0:4])
d.buf = d.buf[4:]
x := d.order.Uint32(d.buf[d.offset : d.offset+4])
d.offset += 4
return x
}
func (e *encoder) uint32(x uint32) {
e.order.PutUint32(e.buf[0:4], x)
e.buf = e.buf[4:]
e.order.PutUint32(e.buf[e.offset:e.offset+4], x)
e.offset += 4
}
func (d *decoder) uint64() uint64 {
x := d.order.Uint64(d.buf[0:8])
d.buf = d.buf[8:]
x := d.order.Uint64(d.buf[d.offset : d.offset+8])
d.offset += 8
return x
}
func (e *encoder) uint64(x uint64) {
e.order.PutUint64(e.buf[0:8], x)
e.buf = e.buf[8:]
e.order.PutUint64(e.buf[e.offset:e.offset+8], x)
e.offset += 8
}
func (d *decoder) int8() int8 { return int8(d.uint8()) }
@ -646,15 +647,16 @@ func (e *encoder) value(v reflect.Value) {
}
func (d *decoder) skip(v reflect.Value) {
d.buf = d.buf[dataSize(v):]
d.offset += dataSize(v)
}
func (e *encoder) skip(v reflect.Value) {
n := dataSize(v)
for i := range e.buf[0:n] {
e.buf[i] = 0
zero := e.buf[e.offset : e.offset+n]
for i := range zero {
zero[i] = 0
}
e.buf = e.buf[n:]
e.offset += n
}
// intDataSize returns the size of the data required to represent the data when encoded.