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Russ Cox e375ca2a25 runtime: reorder bits in heap bitmap bytes 
The runtime deals with 1-bit pointer bitmaps and 2-bit heap bitmaps
that have entries for both pointers and mark bits.

Each byte in a 1-bit pointer bitmap looks like pppppppp (all pointer bits).
Each byte in a 2-bit heap bitmap looks like mpmpmpmp (mark, pointer, ...).
This means that when converting from 1-bit to 2-bit, as we do
during malloc, we have to pick up 4 bits in pppp form and use
shifts to create the mpmpmpmp form.

This CL changes the 2-bit heap bitmap form to mmmmpppp,
so that 4 bits picked up in 1-bit form can be used directly in
the low bits of the heap bitmap byte, without expansion.
This simplifies the code, and it also happens to be faster.

name                    old mean              new mean              delta
SetTypePtr              14.0ns × (0.98,1.09)  14.0ns × (0.98,1.08)     ~    (p=0.966)
SetTypePtr8             16.5ns × (0.99,1.05)  15.3ns × (0.96,1.16)   -6.86% (p=0.012)
SetTypePtr16            21.3ns × (0.98,1.05)  18.8ns × (0.94,1.14)  -11.49% (p=0.000)
SetTypePtr32            34.6ns × (0.93,1.22)  27.7ns × (0.91,1.26)  -20.08% (p=0.001)
SetTypePtr64            55.7ns × (0.97,1.11)  41.6ns × (0.98,1.04)  -25.30% (p=0.000)
SetTypePtr126           98.0ns × (1.00,1.00)  67.7ns × (0.99,1.05)  -30.88% (p=0.000)
SetTypePtr128           98.6ns × (1.00,1.01)  68.6ns × (0.99,1.03)  -30.44% (p=0.000)
SetTypePtrSlice          781ns × (0.99,1.01)   571ns × (0.99,1.04)  -26.93% (p=0.000)
SetTypeNode1            13.1ns × (0.99,1.01)  12.1ns × (0.99,1.01)   -7.45% (p=0.000)
SetTypeNode1Slice        113ns × (0.99,1.01)    94ns × (1.00,1.00)  -16.35% (p=0.000)
SetTypeNode8            32.7ns × (1.00,1.00)  29.8ns × (0.99,1.01)   -8.97% (p=0.000)
SetTypeNode8Slice        266ns × (1.00,1.00)   204ns × (1.00,1.00)  -23.40% (p=0.000)
SetTypeNode64           58.0ns × (0.98,1.08)  42.8ns × (1.00,1.01)  -26.24% (p=0.000)
SetTypeNode64Slice      1.55µs × (0.99,1.02)  0.96µs × (1.00,1.00)  -37.84% (p=0.000)
SetTypeNode64Dead       13.1ns × (0.99,1.01)  12.1ns × (1.00,1.00)   -7.33% (p=0.000)
SetTypeNode64DeadSlice  1.52µs × (1.00,1.01)  1.08µs × (1.00,1.01)  -28.95% (p=0.000)
SetTypeNode124          97.9ns × (1.00,1.00)  67.1ns × (1.00,1.01)  -31.49% (p=0.000)
SetTypeNode124Slice     2.87µs × (0.99,1.02)  1.75µs × (1.00,1.01)  -39.15% (p=0.000)
SetTypeNode126          98.4ns × (1.00,1.01)  68.1ns × (1.00,1.01)  -30.79% (p=0.000)
SetTypeNode126Slice     2.91µs × (0.99,1.01)  1.77µs × (0.99,1.01)  -39.09% (p=0.000)
SetTypeNode1024          732ns × (1.00,1.00)   511ns × (0.87,1.42)  -30.14% (p=0.000)
SetTypeNode1024Slice    23.1µs × (1.00,1.00)  13.9µs × (0.99,1.02)  -39.83% (p=0.000)

Change-Id: I12e3b850a4e6fa6c8146b8635ff728f3ef658819
Reviewed-on: https://go-review.googlesource.com/9828
Reviewed-by: Austin Clements <austin@google.com>
2015-05-11 16:37:36 +00:00
api runtime: remove unused GC times from api.next 2015-05-06 14:49:26 +00:00
doc doc/effective_go: make function signature match function body 2015-05-08 17:01:24 +00:00
lib/time remove the obsolete lib/codereview. 2014-12-08 07:51:54 +00:00
misc misc/trace: add license for the trace-viewer 2015-05-11 06:09:10 +00:00
src runtime: reorder bits in heap bitmap bytes 2015-05-11 16:37:36 +00:00
test cmd/internal/gc: unsafe.Pointer constants may only be converted to uintptr 2015-05-07 23:54:28 +00:00
.gitattributes .gitattributes: prevent all magic line ending changes 2014-12-12 23:14:54 +00:00
.gitignore .gitignore: ignore ARM64 build products 2015-03-16 18:44:22 +00:00
AUTHORS A+C: add another email address for Emil Hessman 2014-11-12 10:01:23 -08:00
CONTRIBUTING.md doc: direct people to the mailing list 2015-01-18 21:27:07 +00:00
CONTRIBUTORS CONTRIBUTORS: add Burcu Dogan's personal mail 2015-05-06 16:06:42 +00:00
favicon.ico godoc: update favicon 2012-10-11 17:02:36 +11:00
LICENSE doc: update licensing text one more time 2012-03-27 15:09:13 +11:00
PATENTS LICENSE: separate, change PATENTS text 2010-12-06 16:31:59 -05:00
README.md doc: fix broken link in README 2015-02-19 05:50:57 +00:00
robots.txt godoc: serve robots.txt raw 2011-02-19 05:46:20 +11:00

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.

Our canonical Git repository is located at https://go.googlesource.com/go. There is a mirror of the repository at https://github.com/golang/go.

Please report issues here: https://golang.org/issue/new

Go is the work of hundreds of contributors. We appreciate your help!

To contribute, please read the contribution guidelines: https://golang.org/doc/contribute.html

Please note that we do not use pull requests.

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.