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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
..
archive archive/tar: style nit: s/nano_buf/nanoBuf/ 2016-04-15 21:29:18 +00:00
bufio all: replace magic 0x80 with named constant utf8.RuneSelf 2016-04-10 15:15:57 +00:00
builtin
bytes all: remove unnecessary type conversions 2016-04-15 07:31:45 +00:00
cmd testing: add matching of subtest 2016-04-21 19:58:31 +00:00
compress compress/flate: use uncompressed if dynamic encoding is larger 2016-04-18 02:30:46 +00:00
container container/heap: correct number of elements in BenchmarkDup 2016-04-20 15:26:05 +00:00
context context: attempt to deflake timing tests 2016-04-11 23:15:02 +00:00
crypto crypto/md5: add assembly implementation on ppc64le 2016-04-20 21:38:01 +00:00
database/sql all: delete dead non-test code 2016-03-25 06:28:13 +00:00
debug debug/pe: introduce Section.Relocs 2016-04-21 06:35:48 +00:00
encoding encoding/json: update docs to not use misuse the term "object" 2016-04-16 22:11:57 +00:00
errors
expvar expvar: Ensure strings are written as valid JSON. 2016-04-06 03:52:39 +00:00
flag
fmt fmt: remove extra space in doc for compound objects 2016-04-17 20:07:32 +00:00
go go/types: trailing semis are ok after valid fallthrough 2016-04-19 21:44:44 +00:00
hash hash/adler32: Unroll loop for extra performance. 2016-04-15 10:17:17 +00:00
html html/template: add examples of loading templates from files 2016-04-13 02:28:28 +00:00
image image/draw: remove some bounds checks from DrawYCbCr 2016-04-17 06:25:28 +00:00
index/suffixarray
internal internal/trace: fix int overflow in timestamps 2016-04-12 07:25:11 +00:00
io io: document WriteString calls Write exactly once 2016-04-12 01:03:51 +00:00
log
math math/big: more tests, documentation for Flot gob marshalling 2016-04-20 21:16:21 +00:00
mime all: standardize RFC mention format 2016-04-12 21:07:52 +00:00
net net: add support for Zone of IPNet 2016-04-19 09:21:57 +00:00
os all: remove unnecessary type conversions 2016-04-15 07:31:45 +00:00
path all: use bytes.Equal, bytes.Contains and strings.Contains, again 2016-04-11 15:16:54 +00:00
reflect reflect: test that method name offset is valid 2016-04-18 19:13:36 +00:00
regexp all: remove unnecessary type conversions 2016-04-15 07:31:45 +00:00
runtime runtime: allocate black during GC 2016-04-21 20:07:22 +00:00
sort all: delete dead non-test code 2016-03-25 06:28:13 +00:00
strconv strconv: fix ParseFloat for special forms of zero values 2016-04-19 22:39:43 +00:00
strings all: remove unnecessary type conversions 2016-04-15 07:31:45 +00:00
sync all: remove unnecessary type conversions 2016-04-15 07:31:45 +00:00
syscall syscall: fix epoll_event struct for ppc64le/ppc64 2016-04-13 20:58:46 +00:00
testing testing: add matching of subtest 2016-04-21 19:58:31 +00:00
text text/template: emit field error over nil pointer error where appropriate 2016-04-10 23:29:29 +00:00
time all: remove unnecessary type conversions 2016-04-15 07:31:45 +00:00
unicode all: remove unnecessary type conversions 2016-04-15 07:31:45 +00:00
unsafe
vendor/golang.org/x/net/http2/hpack all: fix spelling mistakes 2016-04-03 17:03:15 +00:00
all.bash
all.bat
all.rc
androidtest.bash
bootstrap.bash
buildall.bash
clean.bash
clean.bat
clean.rc
iostest.bash
make.bash cmd/dist: redo flag-passing for bootstrap 2016-03-18 19:00:03 +00:00
make.bat
Make.dist
make.rc
naclmake.bash src: split nacltest.bash into naclmake.bash and keep nacltest.bash 2016-04-12 02:03:34 +00:00
nacltest.bash src: split nacltest.bash into naclmake.bash and keep nacltest.bash 2016-04-12 02:03:34 +00:00
race.bash
race.bat
run.bash
run.bat
run.rc