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Albert Nigmatzianov 098eb01600 io: Improve performance of CopyN
Benchmarks:
name          old time/op    new time/op    delta
CopyNSmall-4    5.09µs ± 1%    2.25µs ±86%  -55.91%  (p=0.000 n=11+14)
CopyNLarge-4     114µs ±73%     121µs ±72%     ~     (p=0.701 n=14+14)

name          old alloc/op   new alloc/op   delta
CopyNSmall-4    34.6kB ± 0%     1.9kB ±19%  -94.60%  (p=0.000 n=12+14)
CopyNLarge-4     129kB ± 8%     127kB ±18%   -2.00%  (p=0.007 n=14+14)

name          old allocs/op  new allocs/op  delta
CopyNSmall-4      2.00 ± 0%      1.00 ± 0%  -50.00%  (p=0.000 n=14+14)
CopyNLarge-4      2.00 ± 0%      1.00 ± 0%  -50.00%  (p=0.000 n=14+14)

Benchmark code:
type Buffer struct {
	bytes.Buffer
	io.ReaderFrom
}

func BenchmarkCopyNSmall(b *testing.B) {
	bs := bytes.Repeat([]byte{0}, 1024)
	rd := bytes.NewReader(bs)
	buf := new(Buffer)
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		io.CopyN(buf, rd, 512)
		rd.Reset(bs)
	}
}

func BenchmarkCopyNLarge(b *testing.B) {
	bs := bytes.Repeat([]byte{0}, 64*1024)
	rd := bytes.NewReader(bs)
	buf := new(Buffer)
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		io.CopyN(buf, rd, (32*1024)+1)
		rd.Reset(bs)
	}
}

Change-Id: Id8d29e55758452c870cf372db640f07baec05849
Reviewed-on: https://go-review.googlesource.com/60630
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
2017-09-20 13:41:50 +00:00
.github .github: update ISSUE_TEMPLATE to be closer to 'go bug' 2017-08-19 04:06:10 +00:00
api doc, api: add syscall.SysProcAttr.AmbientCaps change to 1.9 notes, API 2017-06-29 03:29:46 +00:00
doc spec: state which predeclared types are defined or alias types (clarification) 2017-09-19 14:33:25 +00:00
lib/time time: vendor tzdata-2017b and update test 2017-06-07 21:23:58 +00:00
misc misc/cgo/errors: don't pass -C to compiler 2017-09-14 04:02:01 +00:00
src io: Improve performance of CopyN 2017-09-20 13:41:50 +00:00
test cmd/compile: fix stack frame info for calls in receiver slot 2017-09-19 18:35:24 +00:00
.gitattributes .gitattributes: prevent all magic line ending changes 2014-12-12 23:14:54 +00:00
.gitignore .gitignore: include only Go project artifiacts 2017-08-15 21:37:05 +00:00
AUTHORS A+C: final updates for Go 1.9 2017-07-18 01:47:54 +00:00
CONTRIBUTING.md .github: recommend 'go bug' when filing an issue 2017-07-24 17:18:34 +00:00
CONTRIBUTORS A+C: final updates for Go 1.9 2017-07-18 01:47:54 +00:00
favicon.ico website: recreate 16px and 32px favicon 2016-08-25 15:43:32 +00:00
LICENSE doc: revert copyright date to 2009 2016-06-01 22:40:04 +00:00
PATENTS
README.md readme: add attribution for the Gopher image 2017-02-03 19:39:41 +00:00
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