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Austin Clements 6002e01e34 runtime: allocate black during GC 
Currently we allocate white for most of concurrent marking. This is
based on the classical argument that it produces less floating
garbage, since allocations during GC may not get linked into the heap
and allocating white lets us reclaim these. However, it's not clear
how often this actually happens, especially since our write barrier
shades any pointer as soon as it's installed in the heap regardless of
the color of the slot.

On the other hand, allocating black has several advantages that seem
to significantly outweigh this downside.

1) It naturally bounds the total scan work to the live heap size at
the start of a GC cycle. Allocating white does not, and thus depends
entirely on assists to prevent the heap from growing faster than it
can be scanned.

2) It reduces the total amount of scan work per GC cycle by the size
of newly allocated objects that are linked into the heap graph, since
objects allocated black never need to be scanned.

3) It reduces total write barrier work since more objects will already
be black when they are linked into the heap graph.

This gives a slight overall improvement in benchmarks.

name              old time/op  new time/op  delta
XBenchGarbage-12  2.24ms ± 0%  2.21ms ± 1%  -1.32%  (p=0.000 n=18+17)

name                      old time/op    new time/op    delta
BinaryTree17-12              2.60s ± 3%     2.53s ± 3%  -2.56%  (p=0.000 n=20+20)
Fannkuch11-12                2.08s ± 1%     2.08s ± 0%    ~     (p=0.452 n=19+19)
FmtFprintfEmpty-12          45.1ns ± 2%    45.3ns ± 2%    ~     (p=0.367 n=19+20)
FmtFprintfString-12          131ns ± 3%     129ns ± 0%  -1.60%  (p=0.000 n=20+16)
FmtFprintfInt-12             122ns ± 0%     121ns ± 2%  -0.86%  (p=0.000 n=16+19)
FmtFprintfIntInt-12          187ns ± 1%     186ns ± 1%    ~     (p=0.514 n=18+19)
FmtFprintfPrefixedInt-12     189ns ± 0%     188ns ± 1%  -0.54%  (p=0.000 n=16+18)
FmtFprintfFloat-12           256ns ± 0%     254ns ± 1%  -0.43%  (p=0.000 n=17+19)
FmtManyArgs-12               769ns ± 0%     763ns ± 0%  -0.72%  (p=0.000 n=18+18)
GobDecode-12                7.08ms ± 2%    7.00ms ± 1%  -1.22%  (p=0.000 n=20+20)
GobEncode-12                5.88ms ± 0%    5.88ms ± 1%    ~     (p=0.406 n=18+18)
Gzip-12                      214ms ± 0%     214ms ± 1%    ~     (p=0.103 n=17+18)
Gunzip-12                   37.6ms ± 0%    37.6ms ± 0%    ~     (p=0.563 n=17+17)
HTTPClientServer-12         77.2µs ± 3%    76.9µs ± 2%    ~     (p=0.606 n=20+20)
JSONEncode-12               15.1ms ± 1%    15.2ms ± 2%    ~     (p=0.138 n=19+19)
JSONDecode-12               53.3ms ± 1%    53.1ms ± 1%  -0.33%  (p=0.000 n=19+18)
Mandelbrot200-12            4.04ms ± 1%    4.04ms ± 1%    ~     (p=0.075 n=19+18)
GoParse-12                  3.30ms ± 1%    3.29ms ± 1%  -0.57%  (p=0.000 n=18+16)
RegexpMatchEasy0_32-12      69.5ns ± 1%    69.9ns ± 3%    ~     (p=0.822 n=18+20)
RegexpMatchEasy0_1K-12       237ns ± 1%     237ns ± 0%    ~     (p=0.398 n=19+18)
RegexpMatchEasy1_32-12      69.8ns ± 2%    69.5ns ± 1%    ~     (p=0.090 n=20+16)
RegexpMatchEasy1_1K-12       371ns ± 1%     372ns ± 1%    ~     (p=0.178 n=19+20)
RegexpMatchMedium_32-12      108ns ± 2%     108ns ± 3%    ~     (p=0.124 n=20+19)
RegexpMatchMedium_1K-12     33.9µs ± 2%    34.2µs ± 4%    ~     (p=0.309 n=20+19)
RegexpMatchHard_32-12       1.75µs ± 2%    1.77µs ± 4%  +1.28%  (p=0.018 n=19+18)
RegexpMatchHard_1K-12       52.7µs ± 1%    53.4µs ± 4%  +1.23%  (p=0.013 n=15+18)
Revcomp-12                   354ms ± 1%     359ms ± 4%  +1.27%  (p=0.043 n=20+20)
Template-12                 63.6ms ± 2%    63.7ms ± 2%    ~     (p=0.654 n=20+18)
TimeParse-12                 313ns ± 1%     316ns ± 2%  +0.80%  (p=0.014 n=17+20)
TimeFormat-12                332ns ± 0%     329ns ± 0%  -0.66%  (p=0.000 n=16+16)
[Geo mean]                  51.7µs         51.6µs       -0.09%

Change-Id: I2214a6a0e4f544699ea166073249a8efdf080dc0
Reviewed-on: https://go-review.googlesource.com/21323
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
 		2016-04-21 20:07:22 +00:00
.github doc: update issue template 2016-03-09 00:52:16 +00:00
api api: update next.txt 2016-03-21 07:46:44 +00:00
doc doc/faq: reword the link to the generics proposal 2016-04-20 20:51:52 +00:00
lib/time misc: update timezone database to IANA 2016a 2016-02-03 03:14:59 +00:00
misc cmd/link: use gold when dynamic linking on arm64 2016-04-18 16:14:44 +00:00
src runtime: allocate black during GC 2016-04-21 20:07:22 +00:00
test cmd/compile: reject embedded unsafe.Pointer values 2016-04-21 00:32:01 +00:00
.gitattributes .gitattributes: prevent all magic line ending changes 2014-12-12 23:14:54 +00:00
.gitignore .gitignore: don't ignore y.output 2016-04-17 22:41:13 +00:00
AUTHORS A+C: manual updates 2016-01-08 06:02:39 +00:00
CONTRIBUTING.md doc: use new Gerrit URL and mention our instance in CONTRIBUTING.md 2016-03-09 00:52:42 +00:00
CONTRIBUTORS C: fix jbd's identity 2016-04-07 18:25:13 +00:00
LICENSE doc: update licensing text one more time 2012-03-27 15:09:13 +11:00
PATENTS
…
README.md readme: emphasize issue tracker is for bugs/proposals 2015-10-02 18:44:14 +00:00
favicon.ico godoc: update favicon 2012-10-11 17:02:36 +11:00
robots.txt
…

README.md

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

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For documentation about how to install and use Go, visit https://golang.org/ or load doc/install-source.html in your web browser.

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Note that we do not accept pull requests and that we use the issue tracker for bug reports and proposals only. Please ask questions on https://forum.golangbridge.org or https://groups.google.com/forum/#!forum/golang-nuts.

Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file.

--

Binary Distribution Notes

If you have just untarred a binary Go distribution, you need to set the environment variable $GOROOT to the full path of the go directory (the one containing this file). You can omit the variable if you unpack it into /usr/local/go, or if you rebuild from sources by running all.bash (see doc/install-source.html). You should also add the Go binary directory $GOROOT/bin to your shell's path.

For example, if you extracted the tar file into $HOME/go, you might put the following in your .profile:

export GOROOT=$HOME/go
export PATH=$PATH:$GOROOT/bin

See https://golang.org/doc/install or doc/install.html for more details.