Tag Archives: performance

Go 1.8 toolchain improvements

This is a progress report on the Go toolchain improvements during the 1.8 development cycle.

Now we’re well into November, the 1.8 development window is closing fast on the few remaining in fly change lists, with the remainder being told to wait until the 1.9 development season opens when Go 1.8 ships in February 2017.

For more in this series, read my previous post on the Go 1.8 toolchain improvements from September, and my post on the improvements to the Go toolchain in the 1.7 development cycle.

Faster compilation

Since Go 1.5, released in August 2015, compile times have been significantly slower than Go 1.4. Work on addressing this slow down started in ernest in the Go 1.7 cycle, and is still ongoing.

Robert Griesemer and Matthew Dempsky’s worked on rewriting the parser to make it faster and remove many of the package level variables inherited from the previous yacc based parser. This parser produces a new abstract syntax tree while the rest of the compiler expects the previous yacc syntax tree. For 1.8 the new parser must transform its output into the previous syntax tree for consumption by the rest of the compiler. Even with this extra transformation step the new parser is no slower than the previous version and plans are being made to remove this transformation requirement in Go 1.9.

Compile time for full build relative to Go 1.4.3

Compile time for full build relative to Go 1.4.3

The take away is Go 1.8 is on target to improve compile times by an average of 15% over Go 1.7. Compared to the 3-5% improvements reported two months prior, it’s nice to know that there is still blood in this stone.

Note: The benchmark scripts for jujud, kube-controller-manager, and gogs are online. Please try them yourself and report your findings.

Code generation improvements

The big feature of the previous 1.7 cycle was the new SSA backend for 64 bit Intel. In Go 1.8 the SSA backend has been rolled out to all the other architectures that Go supports and the old backend code has been deleted.

amd64, by virtue of being the most popular production architecture, has always been the fastest. As I reported a few months ago, the results comparing Go 1.8 to Go 1.7 on Intel architectures show middling improvement driven equally by improvements to code generation, escape analysis improvements, and optimisations to the std library.

name                     old time/op    new time/op    delta
BinaryTree17-4              3.04s ± 1%     3.03s ± 0%     ~     (p=0.222 n=5+5)
Fannkuch11-4                3.27s ± 0%     3.39s ± 1%   +3.74%  (p=0.008 n=5+5)
FmtFprintfEmpty-4          60.0ns ± 3%    58.3ns ± 1%   -2.70%  (p=0.008 n=5+5)
FmtFprintfString-4          177ns ± 2%     164ns ± 2%   -7.47%  (p=0.008 n=5+5)
FmtFprintfInt-4             169ns ± 2%     157ns ± 1%   -7.22%  (p=0.008 n=5+5)
FmtFprintfIntInt-4          264ns ± 1%     243ns ± 1%   -8.10%  (p=0.008 n=5+5)
FmtFprintfPrefixedInt-4     254ns ± 2%     244ns ± 1%   -4.02%  (p=0.008 n=5+5)
FmtFprintfFloat-4           357ns ± 1%     348ns ± 2%   -2.35%  (p=0.032 n=5+5)
FmtManyArgs-4              1.10µs ± 1%    0.97µs ± 1%  -11.03%  (p=0.008 n=5+5)
GobDecode-4                9.85ms ± 1%    9.31ms ± 1%   -5.51%  (p=0.008 n=5+5)
GobEncode-4                8.75ms ± 1%    8.17ms ± 1%   -6.67%  (p=0.008 n=5+5)
Gzip-4                      282ms ± 0%     289ms ± 1%   +2.32%  (p=0.008 n=5+5)
Gunzip-4                   50.9ms ± 1%    51.7ms ± 0%   +1.67%  (p=0.008 n=5+5)
HTTPClientServer-4          195µs ± 1%     196µs ± 1%     ~     (p=0.095 n=5+5)
JSONEncode-4               21.6ms ± 6%    19.8ms ± 3%   -8.37%  (p=0.008 n=5+5)
JSONDecode-4               70.2ms ± 3%    71.0ms ± 1%     ~     (p=0.310 n=5+5)
Mandelbrot200-4            5.20ms ± 0%    4.73ms ± 1%   -9.05%  (p=0.008 n=5+5)
GoParse-4                  4.38ms ± 3%    4.28ms ± 2%     ~     (p=0.056 n=5+5)
RegexpMatchEasy0_32-4      96.7ns ± 2%    98.1ns ± 0%     ~     (p=0.127 n=5+5)
RegexpMatchEasy0_1K-4       311ns ± 1%     313ns ± 0%     ~     (p=0.214 n=5+5)
RegexpMatchEasy1_32-4      97.9ns ± 2%    89.8ns ± 2%   -8.33%  (p=0.008 n=5+5)
RegexpMatchEasy1_1K-4       519ns ± 0%     510ns ± 2%   -1.70%  (p=0.040 n=5+5)
RegexpMatchMedium_32-4      158ns ± 2%     146ns ± 0%   -7.71%  (p=0.016 n=5+4)
RegexpMatchMedium_1K-4     46.3µs ± 1%    47.8µs ± 2%   +3.12%  (p=0.008 n=5+5)
RegexpMatchHard_32-4       2.53µs ± 3%    2.46µs ± 0%   -2.91%  (p=0.008 n=5+5)
RegexpMatchHard_1K-4       76.1µs ± 0%    74.5µs ± 2%   -2.12%  (p=0.008 n=5+5)
Revcomp-4                   563ms ± 2%     531ms ± 1%   -5.78%  (p=0.008 n=5+5)
Template-4                 86.7ms ± 1%    82.2ms ± 1%   -5.16%  (p=0.008 n=5+5)
TimeParse-4                 433ns ± 3%     399ns ± 4%   -7.90%  (p=0.008 n=5+5)
TimeFormat-4                467ns ± 2%     430ns ± 1%   -7.76%  (p=0.008 n=5+5)

name                     old speed      new speed      delta
GobDecode-4              77.9MB/s ± 1%  82.5MB/s ± 1%   +5.84%  (p=0.008 n=5+5)
GobEncode-4              87.7MB/s ± 1%  94.0MB/s ± 1%   +7.15%  (p=0.008 n=5+5)
Gzip-4                   68.8MB/s ± 0%  67.2MB/s ± 1%   -2.27%  (p=0.008 n=5+5)
Gunzip-4                  381MB/s ± 1%   375MB/s ± 0%   -1.65%  (p=0.008 n=5+5)
JSONEncode-4             89.9MB/s ± 5%  98.1MB/s ± 3%   +9.11%  (p=0.008 n=5+5)
JSONDecode-4             27.6MB/s ± 3%  27.3MB/s ± 1%     ~     (p=0.310 n=5+5)
GoParse-4                13.2MB/s ± 3%  13.5MB/s ± 2%     ~     (p=0.056 n=5+5)
RegexpMatchEasy0_32-4     331MB/s ± 2%   326MB/s ± 0%     ~     (p=0.151 n=5+5)
RegexpMatchEasy0_1K-4    3.29GB/s ± 1%  3.27GB/s ± 0%     ~     (p=0.222 n=5+5)
RegexpMatchEasy1_32-4     327MB/s ± 2%   357MB/s ± 2%   +9.20%  (p=0.008 n=5+5)
RegexpMatchEasy1_1K-4    1.97GB/s ± 0%  2.01GB/s ± 2%   +1.76%  (p=0.032 n=5+5)
RegexpMatchMedium_32-4   6.31MB/s ± 2%  6.83MB/s ± 1%   +8.31%  (p=0.008 n=5+5)
RegexpMatchMedium_1K-4   22.1MB/s ± 1%  21.4MB/s ± 2%   -3.01%  (p=0.008 n=5+5)
RegexpMatchHard_32-4     12.6MB/s ± 3%  13.0MB/s ± 0%   +2.98%  (p=0.008 n=5+5)
RegexpMatchHard_1K-4     13.4MB/s ± 0%  13.7MB/s ± 2%   +2.19%  (p=0.008 n=5+5)
Revcomp-4                 451MB/s ± 2%   479MB/s ± 1%   +6.12%  (p=0.008 n=5+5)
Template-4               22.4MB/s ± 1%  23.6MB/s ± 1%   +5.43%  (p=0.008 n=5+5)

The big improvements from the switch to the SSA backend show up on non intel architectures. Here are the results for Arm64:

name                     old time/op    new time/op     delta
BinaryTree17-8              10.6s ± 0%       8.1s ± 1%  -23.62%  (p=0.016 n=4+5)
Fannkuch11-8                9.19s ± 0%      5.95s ± 0%  -35.27%  (p=0.008 n=5+5)
FmtFprintfEmpty-8           136ns ± 0%      118ns ± 1%  -13.53%  (p=0.008 n=5+5)
FmtFprintfString-8          472ns ± 1%      331ns ± 1%  -29.82%  (p=0.008 n=5+5)
FmtFprintfInt-8             388ns ± 3%      273ns ± 0%  -29.61%  (p=0.008 n=5+5)
FmtFprintfIntInt-8          640ns ± 2%      438ns ± 0%  -31.61%  (p=0.008 n=5+5)
FmtFprintfPrefixedInt-8     580ns ± 0%      423ns ± 0%  -27.09%  (p=0.008 n=5+5)
FmtFprintfFloat-8           823ns ± 0%      613ns ± 1%  -25.57%  (p=0.008 n=5+5)
FmtManyArgs-8              2.69µs ± 0%     1.96µs ± 0%  -27.12%  (p=0.016 n=4+5)
GobDecode-8                24.4ms ± 0%     17.3ms ± 0%  -28.88%  (p=0.008 n=5+5)
GobEncode-8                18.6ms ± 0%     15.1ms ± 1%  -18.65%  (p=0.008 n=5+5)
Gzip-8                      1.20s ± 0%      0.74s ± 0%  -38.02%  (p=0.008 n=5+5)
Gunzip-8                    190ms ± 0%      130ms ± 0%  -31.73%  (p=0.008 n=5+5)
HTTPClientServer-8          205µs ± 1%      166µs ± 2%  -19.27%  (p=0.008 n=5+5)
JSONEncode-8               50.7ms ± 0%     41.5ms ± 0%  -18.10%  (p=0.008 n=5+5)
JSONDecode-8                201ms ± 0%      155ms ± 1%  -22.93%  (p=0.008 n=5+5)
Mandelbrot200-8            13.0ms ± 0%     10.1ms ± 0%  -22.78%  (p=0.008 n=5+5)
GoParse-8                  11.4ms ± 0%      8.5ms ± 0%  -24.80%  (p=0.008 n=5+5)
RegexpMatchEasy0_32-8       271ns ± 0%      225ns ± 0%  -16.97%  (p=0.008 n=5+5)
RegexpMatchEasy0_1K-8      1.69µs ± 0%     1.92µs ± 0%  +13.42%  (p=0.008 n=5+5)
RegexpMatchEasy1_32-8       292ns ± 0%      255ns ± 0%  -12.60%  (p=0.000 n=4+5)
RegexpMatchEasy1_1K-8      2.20µs ± 0%     2.38µs ± 0%   +8.38%  (p=0.008 n=5+5)
RegexpMatchMedium_32-8      411ns ± 0%      360ns ± 0%  -12.41%  (p=0.000 n=5+4)
RegexpMatchMedium_1K-8      118µs ± 0%      104µs ± 0%  -12.07%  (p=0.008 n=5+5)
RegexpMatchHard_32-8       6.83µs ± 0%     5.79µs ± 0%  -15.27%  (p=0.016 n=4+5)
RegexpMatchHard_1K-8        205µs ± 0%      176µs ± 0%  -14.19%  (p=0.008 n=5+5)
Revcomp-8                   2.01s ± 0%      1.43s ± 0%  -29.02%  (p=0.008 n=5+5)
Template-8                  259ms ± 0%      158ms ± 0%  -38.93%  (p=0.008 n=5+5)
TimeParse-8                 874ns ± 1%      733ns ± 1%  -16.16%  (p=0.008 n=5+5)
TimeFormat-8               1.00µs ± 1%     0.86µs ± 1%  -13.88%  (p=0.008 n=5+5)

name                     old speed      new speed       delta
GobDecode-8              31.5MB/s ± 0%   44.3MB/s ± 0%  +40.61%  (p=0.008 n=5+5)
GobEncode-8              41.3MB/s ± 0%   50.7MB/s ± 1%  +22.92%  (p=0.008 n=5+5)
Gzip-8                   16.2MB/s ± 0%   26.1MB/s ± 0%  +61.33%  (p=0.008 n=5+5)
Gunzip-8                  102MB/s ± 0%    150MB/s ± 0%  +46.45%  (p=0.016 n=4+5)
JSONEncode-8             38.3MB/s ± 0%   46.7MB/s ± 0%  +22.10%  (p=0.008 n=5+5)
JSONDecode-8             9.64MB/s ± 0%  12.49MB/s ± 0%  +29.54%  (p=0.016 n=5+4)
GoParse-8                5.09MB/s ± 0%   6.78MB/s ± 0%  +33.02%  (p=0.008 n=5+5)
RegexpMatchEasy0_32-8     118MB/s ± 0%    142MB/s ± 0%  +20.29%  (p=0.008 n=5+5)
RegexpMatchEasy0_1K-8     605MB/s ± 0%    534MB/s ± 0%  -11.85%  (p=0.016 n=5+4)
RegexpMatchEasy1_32-8     110MB/s ± 0%    125MB/s ± 0%  +14.23%  (p=0.029 n=4+4)
RegexpMatchEasy1_1K-8     465MB/s ± 0%    430MB/s ± 0%   -7.72%  (p=0.008 n=5+5)
RegexpMatchMedium_32-8   2.43MB/s ± 0%   2.77MB/s ± 0%  +13.99%  (p=0.016 n=5+4)
RegexpMatchMedium_1K-8   8.68MB/s ± 0%   9.87MB/s ± 0%  +13.71%  (p=0.008 n=5+5)
RegexpMatchHard_32-8     4.68MB/s ± 0%   5.53MB/s ± 0%  +18.08%  (p=0.016 n=4+5)
RegexpMatchHard_1K-8     5.00MB/s ± 0%   5.83MB/s ± 0%  +16.60%  (p=0.008 n=5+5)
Revcomp-8                 126MB/s ± 0%    178MB/s ± 0%  +40.88%  (p=0.008 n=5+5)
Template-8               7.48MB/s ± 0%  12.25MB/s ± 0%  +63.74%  (p=0.008 n=5+5)

These are pretty big improvements from just recompiling your binary.

Defer and cgo improvements

The question of if defer can be used in hot code paths remains open, but during the 1.8 cycle Austin reduced the overhead of using defer by a half, according to some benchmarks.

The runtime package benchmarks are a little less rosy.

name         old time/op  new time/op  delta
Defer-4       101ns ± 1%    66ns ± 0%  -34.73%  (p=0.000 n=20+20)
Defer10-4    93.2ns ± 1%  62.5ns ± 8%  -33.02%  (p=0.000 n=20+20)
DeferMany-4   148ns ± 3%   131ns ± 3%  -11.42%  (p=0.000 n=19+19)

According to them defer improved by a third in most common circumstances where the statement closes over no more than a single variable.

Additionally, an optimisation by David Crawshaw reduced the overhead of defer in the cgo path by nearly half.

name       old time/op  new time/op  delta
CgoNoop-8  93.5ns ± 0%  51.1ns ± 1%  -45.34%  (p=0.016 n=4+5)

One more thing

Go 1.7 supported 64 bit mips platforms, thanks to the work of Minux and Cherry. However, the less powerful but plentiful, 32 bit mips platforms were not supported. As a bonus, thanks to the work of Vladimir Stefanovic, Go 1.8 will ship will support for 32 bit mips.

% env GOARCH=mips go build -o godoc.mips golang.org/x/tools/cmd/godoc
% file godoc.mips 
godoc.mips: ELF 32-bit MSB  executable, MIPS, MIPS32 version 1 (SYSV), statically linked, not stripped

While 32 bit mips hosts are probably too small to compile Go programs natively, you can always cross compile from your development workstation for linux/mips.

Go 1.8 performance improvements, one month in

Sunday September the 18th marks a month since the Go 1.8 cycle opened officially. I’m passionate about the performance of Go programs, and of the compiler itself. This post is a brief look at the state of play, roughly 1/2 way into the development cycle for Go 1.81.

Note: these results are of course preliminary and represent only a point in time, not the performance of the final Go 1.8 release.

Compile times

Nothing much to report here. Using the methodology from my previous Go 1.7 benchmarks, there is a 3.22%–5.11% improvement in full compile time compared to Go 1.7.

Go 1.4.3, Go 1.7, Go tip

Performance improvements

Intel amd64

Better code generation and small improvements to the runtime and standard library show some small improvements for amd642, but really nothing to write home about yet.

name                       old time/op    new time/op  delta
BinaryTree17-4              3.07s ± 2%     3.06s ± 2%    ~      (p=0.661 n=10+9)
Fannkuch11-4                3.23s ± 1%     3.22s ± 0%  -0.43%   (p=0.008 n=9+10)
FmtFprintfEmpty-4          64.4ns ± 0%    61.8ns ± 4%  -4.17%   (p=0.005 n=9+10)
FmtFprintfString-4          162ns ± 0%     162ns ± 0%    ~      (p=0.065 n=10+9)
FmtFprintfInt-4             142ns ± 0%     142ns ± 0%    ~      (p=0.137 n=8+10)
FmtFprintfIntInt-4          220ns ± 0%     217ns ± 0%  -1.18%   (p=0.000 n=9+10)
FmtFprintfPrefixedInt-4     224ns ± 0%     224ns ± 1%    ~       (p=0.206 n=9+9)
FmtFprintfFloat-4           313ns ± 0%     312ns ± 0%  -0.26%   (p=0.001 n=10+9)
FmtManyArgs-4               906ns ± 0%     894ns ± 0%  -1.32%    (p=0.000 n=7+6)
GobDecode-4                8.88ms ± 1%    8.81ms ± 0%  -0.81%  (p=0.003 n=10+10)
GobEncode-4                7.93ms ± 1%    7.88ms ± 0%  -0.66%   (p=0.008 n=9+10)
Gzip-4                      272ms ± 1%     277ms ± 0%  +1.95%   (p=0.000 n=10+9)
Gunzip-4                   47.4ms ± 0%    47.4ms ± 0%    ~      (p=0.720 n=9+10)
HTTPClientServer-4          201µs ± 4%     202µs ± 2%    ~     (p=0.631 n=10+10)
JSONEncode-4               19.3ms ± 0%    19.3ms ± 0%    ~     (p=0.063 n=10+10)
JSONDecode-4               61.0ms ± 0%    61.2ms ± 0%  +0.33%   (p=0.000 n=10+8)
Mandelbrot200-4            5.20ms ± 0%    5.20ms ± 0%    ~      (p=0.475 n=10+7)
GoParse-4                  3.95ms ± 1%    3.97ms ± 1%  +0.65%    (p=0.003 n=9+9)
RegexpMatchEasy0_32-4      88.4ns ± 0%    88.7ns ± 0%  +0.34%   (p=0.001 n=10+9)
RegexpMatchEasy0_1K-4      1.14µs ± 0%    1.14µs ± 0%    ~       (p=0.369 n=9+6)
RegexpMatchEasy1_32-4      82.6ns ± 0%    82.0ns ± 0%  -0.70%   (p=0.000 n=9+10)
RegexpMatchEasy1_1K-4       469ns ± 0%     463ns ± 0%  -1.23%    (p=0.000 n=6+9)
RegexpMatchMedium_32-4      138ns ± 1%     136ns ± 0%  -1.38%   (p=0.000 n=10+9)
RegexpMatchMedium_1K-4     43.6µs ± 1%    42.0µs ± 0%  -3.74%    (p=0.000 n=9+9)
RegexpMatchHard_32-4       2.25µs ± 1%    2.23µs ± 0%  -0.57%    (p=0.000 n=8+8)
RegexpMatchHard_1K-4       68.8µs ± 0%    68.6µs ± 0%  -0.37%    (p=0.000 n=8+8)
Revcomp-4                   477ms ± 1%     472ms ± 0%  -1.03%    (p=0.000 n=8+8)
Template-4                 76.1ms ± 0%    76.4ms ± 0%  +0.35%    (p=0.000 n=9+9)
TimeParse-4                 367ns ± 0%     366ns ± 0%  -0.16%   (p=0.003 n=10+8)
TimeFormat-4                386ns ± 0%     384ns ± 0%  -0.58%    (p=0.000 n=9+9)

name                     old speed      new speed      delta
GobDecode-4              86.4MB/s ± 1%  87.1MB/s ± 0%  +0.81%  (p=0.003 n=10+10)
GobEncode-4              96.7MB/s ± 1%  97.4MB/s ± 0%  +0.66%   (p=0.007 n=9+10)
Gzip-4                   71.4MB/s ± 1%  70.0MB/s ± 0%  -1.91%   (p=0.000 n=10+9)
Gunzip-4                  409MB/s ± 0%   410MB/s ± 0%    ~      (p=0.703 n=9+10)
JSONEncode-4              101MB/s ± 0%   100MB/s ± 0%    ~     (p=0.084 n=10+10)
JSONDecode-4             31.8MB/s ± 0%  31.7MB/s ± 0%  -0.33%   (p=0.000 n=10+8)
GoParse-4                14.7MB/s ± 1%  14.6MB/s ± 1%  -0.67%    (p=0.002 n=9+9)
RegexpMatchEasy0_32-4     362MB/s ± 0%   361MB/s ± 0%  -0.36%   (p=0.000 n=10+9)
RegexpMatchEasy0_1K-4     898MB/s ± 0%   898MB/s ± 0%    ~       (p=0.762 n=9+8)
RegexpMatchEasy1_32-4     387MB/s ± 0%   390MB/s ± 0%  +0.70%   (p=0.000 n=9+10)
RegexpMatchEasy1_1K-4    2.18GB/s ± 0%  2.21GB/s ± 0%  +1.20%    (p=0.000 n=9+9)
RegexpMatchMedium_32-4   7.23MB/s ± 1%  7.32MB/s ± 0%  +1.19%   (p=0.000 n=10+9)
RegexpMatchMedium_1K-4   23.5MB/s ± 1%  24.4MB/s ± 0%  +3.88%    (p=0.000 n=9+9)
RegexpMatchHard_32-4     14.2MB/s ± 1%  14.3MB/s ± 0%  +0.58%    (p=0.000 n=8+8)
RegexpMatchHard_1K-4     14.9MB/s ± 0%  14.9MB/s ± 0%  +0.34%    (p=0.000 n=8+7)
Revcomp-4                 533MB/s ± 1%   539MB/s ± 0%  +1.04%    (p=0.000 n=8+8)
Template-4               25.5MB/s ± 0%  25.4MB/s ± 0%  -0.36%    (p=0.000 n=9+9)


The major improvement that landed recently in the development branch is the conversion of the remaining architecture backends to use the compiler’s SSA form. This has brought a substantial improvement in generated code for non Intel architectures, like ARM3.

name                       old time/op    new time/op    delta
BinaryTree17-4              33.8s ± 1%      27.7s ± 0%  -18.06%  (p=0.000 n=10+10)
Fannkuch11-4                42.0s ± 0%      19.3s ± 0%  -54.10%  (p=0.000 n=10+10)
FmtFprintfEmpty-4           670ns ± 1%      581ns ± 1%  -13.30%  (p=0.000 n=10+10)
FmtFprintfString-4         2.04µs ± 1%     1.65µs ± 0%  -19.09%  (p=0.000 n=10+10)
FmtFprintfInt-4            1.71µs ± 0%     1.21µs ± 0%  -29.39%   (p=0.000 n=10+9)
FmtFprintfIntInt-4         2.69µs ± 1%     1.94µs ± 0%  -27.77%  (p=0.000 n=10+10)
FmtFprintfPrefixedInt-4    2.70µs ± 0%     1.85µs ± 0%  -31.41%   (p=0.000 n=10+9)
FmtFprintfFloat-4          5.15µs ± 0%     3.65µs ± 0%  -29.01%   (p=0.000 n=9+10)
FmtManyArgs-4              11.3µs ± 0%      8.5µs ± 0%  -24.79%   (p=0.000 n=10+9)
GobDecode-4                 112ms ± 0%       77ms ± 1%  -31.04%    (p=0.000 n=9+9)
GobEncode-4                88.5ms ± 1%     77.2ms ± 1%  -12.78%  (p=0.000 n=10+10)
Gzip-4                      4.79s ± 0%      3.34s ± 0%  -30.18%    (p=0.000 n=9+9)
Gunzip-4                    702ms ± 0%      463ms ± 0%  -34.05%  (p=0.000 n=10+10)
HTTPClientServer-4          645µs ± 3%      571µs ± 3%  -11.45%  (p=0.000 n=10+10)
JSONEncode-4                227ms ± 0%      186ms ± 0%  -18.16%  (p=0.000 n=10+10)
JSONDecode-4                845ms ± 0%      618ms ± 0%  -26.81%  (p=0.000 n=10+10)
Mandelbrot200-4            59.3ms ± 0%     40.0ms ± 0%  -32.47%  (p=0.000 n=10+10)
GoParse-4                  45.0ms ± 0%     37.0ms ± 0%  -17.68%    (p=0.000 n=9+9)
RegexpMatchEasy0_32-4       974ns ± 0%      878ns ± 0%   -9.81%   (p=0.000 n=10+9)
RegexpMatchEasy0_1K-4      4.60µs ± 0%     4.48µs ± 0%   -2.57%  (p=0.000 n=10+10)
RegexpMatchEasy1_32-4      1.02µs ± 0%     0.94µs ± 0%   -8.08%   (p=0.000 n=8+10)
RegexpMatchEasy1_1K-4      6.92µs ± 0%     6.08µs ± 0%  -12.10%  (p=0.000 n=10+10)
RegexpMatchMedium_32-4     1.61µs ± 0%     1.27µs ± 0%  -20.98%    (p=0.000 n=9+6)
RegexpMatchMedium_1K-4      447µs ± 0%      317µs ± 0%  -29.05%   (p=0.000 n=10+9)
RegexpMatchHard_32-4       24.9µs ± 0%     18.4µs ± 0%  -25.89%  (p=0.000 n=10+10)
RegexpMatchHard_1K-4        740µs ± 0%      552µs ± 0%  -25.36%  (p=0.000 n=10+10)
Revcomp-4                  81.0ms ± 1%     65.2ms ± 0%  -19.53%    (p=0.000 n=9+9)
Template-4                  1.17s ± 0%      0.81s ± 0%  -31.28%    (p=0.000 n=9+9)
TimeParse-4                5.52µs ± 0%     3.79µs ± 0%  -31.42%   (p=0.000 n=10+9)
TimeFormat-4               10.6µs ± 0%      8.5µs ± 0%  -19.14%  (p=0.000 n=10+10)

name                     old speed      new speed        delta
GobDecode-4              6.86MB/s ± 0%   9.95MB/s ± 1%  +45.00%    (p=0.000 n=9+9)
GobEncode-4              8.67MB/s ± 1%   9.94MB/s ± 1%  +14.69%  (p=0.000 n=10+10)
Gzip-4                   4.05MB/s ± 0%   5.81MB/s ± 0%  +43.32%   (p=0.000 n=10+9)
Gunzip-4                 27.6MB/s ± 0%   41.9MB/s ± 0%  +51.63%  (p=0.000 n=10+10)
JSONEncode-4             8.53MB/s ± 0%  10.43MB/s ± 0%  +22.20%  (p=0.000 n=10+10)
JSONDecode-4             2.30MB/s ± 0%   3.14MB/s ± 0%  +36.39%   (p=0.000 n=9+10)
GoParse-4                1.29MB/s ± 0%   1.56MB/s ± 0%  +20.93%   (p=0.000 n=9+10)
RegexpMatchEasy0_32-4    32.8MB/s ± 0%   36.4MB/s ± 0%  +10.87%  (p=0.000 n=10+10)
RegexpMatchEasy0_1K-4     222MB/s ± 0%    228MB/s ± 0%   +2.64%  (p=0.000 n=10+10)
RegexpMatchEasy1_32-4    31.3MB/s ± 0%   34.0MB/s ± 0%   +8.75%   (p=0.000 n=9+10)
RegexpMatchEasy1_1K-4     148MB/s ± 0%    168MB/s ± 0%  +13.76%  (p=0.000 n=10+10)
RegexpMatchMedium_32-4    620kB/s ± 0%    790kB/s ± 0%  +27.42%   (p=0.000 n=10+8)
RegexpMatchMedium_1K-4   2.29MB/s ± 0%   3.23MB/s ± 0%  +41.05%  (p=0.000 n=10+10)
RegexpMatchHard_32-4     1.29MB/s ± 0%   1.74MB/s ± 0%  +34.88%   (p=0.000 n=9+10)
RegexpMatchHard_1K-4     1.38MB/s ± 0%   1.85MB/s ± 0%  +34.06%  (p=0.000 n=10+10)
Revcomp-4                31.4MB/s ± 1%   39.0MB/s ± 0%  +24.26%    (p=0.000 n=9+9)
Template-4               1.65MB/s ± 0%   2.41MB/s ± 0%  +45.71%   (p=0.000 n=10+9)


  1. Despite the Go 1.8 development cycle opening 18 days late, in order to keep to the 6 month cadence, the feature freeze for this cycle will still occur on the 1st of November.
  2. Intel(R) Core(TM) i5-2520M CPU @ 2.50GHz, 3.13.0-95-generic #142-Ubuntu
  3. Freescale i.MX6, 3.14.77-1-ARCH

Go 1.7 toolchain improvements

This is a progress report on the Go toolchain improvements during the 1.7 development cycle. All measurements were taken using a Thinkpad x220, Core i5-2520M, running Ubuntu 14.04 linux.

Faster compilation

Since Go 1.5, when the compiler itself was translated from C to Go, compile times are slower than they used to be. Everyone knows it, nobody is happy about it, and we’re working on fixing it.

A huge amount of effort in the 1.7 cycle has gone into reducing the amount of memory and the wall time the compiler uses for various benchmark jobs. The results so far are:

Compile time for full build relative to Go 1.4.3

Compile time for full build relative to Go 1.4.3

Previously I reported the current 1.7 compiler was 2x slower than Go 1.4.3 for the Jujud test. After re-benchmarking everything for this post, the slowdown is closer to 2.2x. Jujud is the largest of the three benchmarks–512 packages, vs 304 and 102 packages respectively–and shows the largest slowdown.

The cmd/go result is a little misleading as the code being compiled changes with every release, vs the fixed codebases of the other benchmarks.

Note: The benchmark scripts for jujud, kube-controller-manager, and gogs are online. Please try them yourself and report your findings.

Improved linker performance

A significant part of the build time improvements observed above come from improvements to the linker. Relative to Go 1.6, the linker is now roughly 66% faster.

Link time relative to Go 1.4.3

Link time relative to Go 1.4.3

Relative to Go 1.4.3, linking is 10% faster for any non trivial binary, and up to 30% faster for large binaries like jujud. These figures are for ELF targets only, Mach-o and PE targets have not improved as much.

This isn’t just useful for building final binaries. A faster linker improves the edit/compile/test cycle as each test is itself a program that must be linked and run. Anecdotally the linker now uses a third less memory, which is valuable when linking large binaries.

Smaller binaries

With code generation and linker improvements, binaries produced by the tip compiler are substantially smaller than Go 1.6. This work has been spearheaded by David Crawshaw.

Binary sizes

Binary size (bytes)

At this point, with the exception of its own cmd/go tool, Go 1.7 produces smaller binaries than Go 1.4.3.

Code generation improvements

The big feature for the Go 1.7 cycle is the new SSA backend for 64bit Intel.

While not the focus of this post, it would be remiss not to include some information about performance improvements in compiled code (not just the compiler’s code). Stressing of course that these are preliminary figures as there is still four months to go before the new backend becomes the default for amd64.

Go 1 benchmarks, Go 1.6 vs 683448a

Go 1 benchmarks, Go 1.6 vs 683448a

These numbers match the figures reported by Keith Randall a few weeks ago, and are in line with his thesis in the SSA design doc.

I think it would be fairly easy to make the generated programs 20% smaller and 10% faster. — khr

These improvements are not just the work of the SSA backend. The standard library and garbage collector continue to see improvements, including a 20% improvement to the fmt package by Martin Möhrmann. These benefits flow to all the platforms that Go supports.

The sole regression above is caused by a current limitation in the register optimiser which manages to registerise one less variable in the Mandelbrot inner loop.

Looking ahead

According to the release schedule, approximately one month remains before the 1.7 change window closes and the dev cycle enters the bug fix phase. There is still lots of work to do, but the improvements so far will easily make Go 1.7 the best Go release to date.

Visualising the Go garbage collector

Update this post is also available in Japanese.

This is a post about an experimental tool that I have been working on.

gcvis is a simple way of visualising the operation of the garbage collector within a Go process. Here is a screenshot of it in operation.
The rest of this article explores how gcvis works and how to interpret its results.

How does gcvis get the data ?

There are a few ways you can interrogate a Go program.

You could use the built in profiler, via the net/http/pprof package, or my profile package. However this means modifying the source of the program, which sometimes may not be an option.

There is another source of telemetry data built into every Go program which is accessible by setting the following environment variable.


(The GODEBUG environment variable is documented in the runtime package).

When your program is started with this environment variable set, the following additional output will be printed to standard out (slightly abridged)

 % env GODEBUG=gctrace=1 godoc -http=:6060
gc76(1): 2+1+1390+1 us, 1 -> 3 MB, 16397 (1015746-999349) objects, 1436/1/0 sweeps, 0(0) handoff, 0(0) steal, 0/0/0 yields
gc77(1): 2+0+1582+1 us, 2 -> 4 MB, 14623 (1016248-1001625) objects, 1436/0/0 sweeps, 0(0) handoff, 0(0) steal, 0/0/0 yields
scvg0: inuse: 6, idle: 15, sys: 22, released: 0, consumed: 22 (MB)
scvg1: inuse: 6, idle: 15, sys: 22, released: 0, consumed: 22 (MB)
gc78(1): 5+1+4814+1 us, 2 -> 2 MB, 21076 (1023168-1002092) objects, 1436/25/0 sweeps, 0(0) handoff, 0(0) steal, 0/0/0 yields
scvg2: GC forced
scvg2: inuse: 6, idle: 15, sys: 22, released: 0, consumed: 22 (MB)

The two types of information presented are

  • A line for every garbage collection cycle, indicated by the gc prefix.
  • A set of lines for the operation of the scavenger, indicated by the scvg prefix, which is responsible for returning unused portions of the heap to the operating system.

In the next section I will discuss using, and interpreting the data from, gcvis.

Using gcvis

To use gcvis, place it in front of the Go program you want to inspect, as you would time or nice.

Here is an example of using gcvis with godoc in indexing mode (so it uses lots of memory and cpu time, generating interesting data).

% gcvis godoc -index -http=:6060
2014/07/11 16:29:12 opening browser window, if this fails, navigate to
Created new window in existing browser session.

That’s it.

gcvis takes care of setting the appropriate value of GODEBUG and filtering out the additional information generated. gcvis also tries to open a browser window to view the visualisation. This functionality is provided by pkg/browser and is somewhat operating system dependent.

Because gcvis is recording the gc debug lines in real time, it can add timestamp information to them, a feature which is currently missing from that raw GODEBUG output.

Screenshot from 2014-07-11 16:35:09
In this example you can see the frequency of gc cycles decrease as the heap grows.

The main use of the gc debug data is to record the size of the live objects on the heap, however this doesn’t reveal the total size of the heap, nor what percentage of the heap the live set represents. For that we need to add the debugging information from the scavenger.

The scavenger runs on a timer, currently every two minutes, so will only start to report its data to gcviz a few minutes after the program starts. Here is an example after running for about 15 minutes.

Screenshot from 2014-07-11 17:01:31
Some interesting points to note in this graph are

  • scvg.sys represents the total amount of memory requested from the operating system, this is roughly analogous to the VSS value reported by tools like top.
  • scvg.inuse is the amount of memory in use by the whole heap, which may include dead objects. scvg.inuse and gc.heapinuse may not track each other exactly as they are reported at different times.
  • scvg.idle represents memory that is currently unused by the garbage collector, that is, used to contain dead objects, but is now unused after garbage collection.
  • When the scavenger runs, scvg.idle grows as scvg.inuse shrinks.
  • If memory remains idle for long enough the scavenger will inform the operating system that it is no longer needed, this is reported by scvg.released and matches a drop in scvg.consumedThe operating system is free to ignore this request, and frequently does.


The code is open source on Github, so go get it and try it on your application.

go get -u -v github.com/davecheney/gcvis

I’m very keen to hear from other Go users if gcvis is useful for you. Pull requests and bug reports are also most welcome.

A special thanks to Damian Gryski, Matthew Holt, and Bill Kennedy, for their suggestions and feedback.

Five things that make Go fast

Anthony Starks has remixed my original Google Present based slides using his fantastic Deck presentation tool. You can check out his remix over on his blog, mindchunk.blogspot.com.au/2014/06/remixing-with-deck.

I was recently invited to give a talk at Gocon, a fantastic Go conference held semi-annually in Tokyo, Japan. Gocon 2014 was an entirely community-run one day event combining training and an afternoon of presentations surrounding the theme of Go in production.

The following is the text of my presentation. The original text was structured to force me to speak slowly and clearly, so I have taken the liberty of editing it slightly to be more readable.

I want to thank Bill Kennedy, Minux Ma, and especially Josh Bleecher Snyder, for their assistance in preparing this talk.

Good afternoon.

My name is David.

I am delighted to be here at Gocon today. I have wanted to come to this conference for two years and I am very grateful to the organisers for extending me the opportunity to present to you today.

Gocon 2014
I want to begin my talk with a question.

Why are people choosing to use Go ?

When people talk about their decision to learn Go, or use it in their product, they have a variety of answers, but there always three that are at the top of their list

Gocon 2014
These are the top three.

The first, Concurrency.

Go’s concurrency primitives are attractive to programmers who come from single threaded scripting languages like Nodejs, Ruby, or Python, or from languages like C++ or Java with their heavyweight threading model.

Ease of deployment.

We have heard today from experienced Gophers who appreciate the simplicity of deploying Go applications.

Gocon 2014

This leaves Performance.

I believe an important reason why people choose to use Go is because it is fast.

Gocon 2014 (4)

For my talk today I want to discuss five features that contribute to Go’s performance.

I will also share with you the details of how Go implements these features.

Gocon 2014 (5)

The first feature I want to talk about is Go’s efficient treatment and storage of values.

Gocon 2014 (6)

This is an example of a value in Go. When compiled, gocon consumes exactly four bytes of memory.

Let’s compare Go with some other languages

Gocon 2014 (7)

Due to the overhead of the way Python represents variables, storing the same value using Python consumes six times more memory.

This extra memory is used by Python to track type information, do reference counting, etc

Let’s look at another example:

Gocon 2014 (8)

Similar to Go, the Java int type consumes 4 bytes of memory to store this value.

However, to use this value in a collection like a List or Map, the compiler must convert it into an Integer object.

Gocon 2014 (9)

So an integer in Java frequently looks more like this and consumes between 16 and 24 bytes of memory.

Why is this important ? Memory is cheap and plentiful, why should this overhead matter ?

Gocon 2014 (10)

This is a graph showing CPU clock speed vs memory bus speed.

Notice how the gap between CPU clock speed and memory bus speed continues to widen.

The difference between the two is effectively how much time the CPU spends waiting for memory.

Gocon 2014 (11)

Since the late 1960’s CPU designers have understood this problem.

Their solution is a cache, an area of smaller, faster memory which is inserted between the CPU and main memory.

Gocon 2014 (12)

This is a Location type which holds the location of some object in three dimensional space. It is written in Go, so each Location consumes exactly 24 bytes of storage.

We can use this type to construct an array type of 1,000 Locations, which consumes exactly 24,000 bytes of memory.

Inside the array, the Location structures are stored sequentially, rather than as pointers to 1,000 Location structures stored randomly.

This is important because now all 1,000 Location structures are in the cache in sequence, packed tightly together.

Gocon 2014 (13)

Go lets you create compact data structures, avoiding unnecessary indirection.

Compact data structures utilise the cache better.

Better cache utilisation leads to better performance.

Gocon 2014 (14)

Function calls are not free.

Gocon 2014 (15)

Three things happen when a function is called.

A new stack frame is created, and the details of the caller recorded.

Any registers which may be overwritten during the function call are saved to the stack.

The processor computes the address of the function and executes a branch to that new address.

Gocon 2014 (16)

Because function calls are very common operations, CPU designers have worked hard to optimise this procedure, but they cannot eliminate the overhead.

Depending on what the function does, this overhead may be trivial or significant.

A solution to reducing function call overhead is an optimisation technique called Inlining.

Gocon 2014 (17)

The Go compiler inlines a function by treating the body of the function as if it were part of the caller.

Inlining has a cost; it increases binary size.

It only makes sense to inline when the overhead of calling a function is large relative to the work the function does, so only simple functions are candidates for inlining.

Complicated functions are usually not dominated by the overhead of calling them and are therefore not inlined.

Gocon 2014 (18)

This example shows the function Double calling util.Max.

To reduce the overhead of the call to util.Max, the compiler can inline util.Max into Double, resulting in something like this

Gocon 2014 (19)

After inlining there is no longer a call to util.Max, but the behaviour of Double is unchanged.

Inlining isn’t exclusive to Go. Almost every compiled or JITed language performs this optimisation. But how does inlining in Go work?

The Go implementation is very simple. When a package is compiled, any small function that is suitable for inlining is marked and then compiled as usual.

Then both the source of the function and the compiled version are stored.

Gocon 2014 (20)

This slide shows the contents of util.a. The source has been transformed a little to make it easier for the compiler to process quickly.

When the compiler compiles Double it sees that util.Max is inlinable, and the source of util.Max is available.

Rather than insert a call to the compiled version of util.Max, it can substitute the source of the original function.

Having the source of the function enables other optimizations.

Gocon 2014 (21)

In this example, although the function Test always returns false, Expensive cannot know that without executing it.

When Test is inlined, we get something like this

Gocon 2014 (22)

The compiler now knows that the expensive code is unreachable.

Not only does this save the cost of calling Test, it saves compiling or running any of the expensive code that is now unreachable.

The Go compiler can automatically inline functions across files and even across packages. This includes code that calls inlinable functions from the standard library.

Gocon 2014 (23)

Mandatory garbage collection makes Go a simpler and safer language.

This does not imply that garbage collection makes Go slow, or that garbage collection is the ultimate arbiter of the speed of your program.

What it does mean is memory allocated on the heap comes at a cost. It is a debt that costs CPU time every time the GC runs until that memory is freed.

Gocon 2014 (24)

There is however another place to allocate memory, and that is the stack.

Unlike C, which forces you to choose if a value will be stored on the heap, via malloc, or on the stack, by declaring it inside the scope of the function, Go implements an optimisation called escape analysis.

Gocon 2014 (25)

Escape analysis determines whether any references to a value escape the function in which the value is declared.

If no references escape, the value may be safely stored on the stack.

Values stored on the stack do not need to be allocated or freed.

Lets look at some examples

Gocon 2014 (26)

Sum adds the numbers between 1 and 100 and returns the result. This is a rather unusual way to do this, but it illustrates how Escape Analysis works.

Because the numbers slice is only referenced inside Sum, the compiler will arrange to store the 100 integers for that slice on the stack, rather than the heap.

There is no need to garbage collect numbers, it is automatically freed when Sum returns.

Gocon 2014 (27)

This second example is also a little contrived. In CenterCursor we create a new Cursor and store a pointer to it in c.

Then we pass c to the Center() function which moves the Cursor to the center of the screen.

Then finally we print the X and Y locations of that Cursor.

Even though c was allocated with the new function, it will not be stored on the heap, because no reference c escapes the CenterCursor function.

Gocon 2014 (28)

Go’s optimisations are always enabled by default. You can see the compiler’s escape analysis and inlining decisions with the -gcflags=-m switch.

Because escape analysis is performed at compile time, not run time, stack allocation will always be faster than heap allocation, no matter how efficient your garbage collector is.

I will talk more about the stack in the remaining sections of this talk.

Gocon 2014 (30)

Go has goroutines. These are the foundations for concurrency in Go.

I want to step back for a moment and explore the history that leads us to goroutines.

In the beginning computers ran one process at a time. Then in the 60’s the idea of multiprocessing, or time sharing became popular.

In a time-sharing system the operating systems must constantly switch the attention of the CPU between these processes by recording the state of the current process, then restoring the state of another.

This is called process switching.

Gocon 2014 (29)

There are three main costs of a process switch.

First is the kernel needs to store the contents of all the CPU registers for that process, then restore the values for another process.

The kernel also needs to flush the CPU’s mappings from virtual memory to physical memory as these are only valid for the current process.

Finally there is the cost of the operating system context switch, and the overhead of the scheduler function to choose the next process to occupy the CPU.

Gocon 2014 (31)

There are a surprising number of registers in a modern processor. I have difficulty fitting them on one slide, which should give you a clue how much time it takes to save and restore them.

Because a process switch can occur at any point in a process’ execution, the operating system needs to store the contents of all of these registers because it does not know which are currently in use.

Gocon 2014 (32)

This lead to the development of threads, which are conceptually the same as processes, but share the same memory space.

As threads share address space, they are lighter than processes so are faster to create and faster to switch between.

Gocon 2014 (33)

Goroutines take the idea of threads a step further.

Goroutines are cooperatively scheduled, rather than relying on the kernel to manage their time sharing.

The switch between goroutines only happens at well defined points, when an explicit call is made to the Go runtime scheduler.

The compiler knows the registers which are in use and saves them automatically.

Gocon 2014 (34)

While goroutines are cooperatively scheduled, this scheduling is handled for you by the runtime.

Places where Goroutines may yield to others are:

  • Channel send and receive operations, if those operations would block.
  • The Go statement, although there is no guarantee that new goroutine will be scheduled immediately.
  • Blocking syscalls like file and network operations.
  • After being stopped for a garbage collection cycle.

Gocon 2014 (35)

This an example to illustrate some of the scheduling points described in the previous slide.

The thread, depicted by the arrow, starts on the left in the ReadFile function. It encounters os.Open, which blocks the thread while waiting for the file operation to complete, so the scheduler switches the thread to the goroutine on the right hand side.

Execution continues until the read from the c chan blocks, and by this time the os.Open call has completed so the scheduler switches the thread back the left hand side and continues to the file.Read function, which again blocks on file IO.

The scheduler switches the thread back to the right hand side for another channel operation, which has unblocked during the time the left hand side was running, but it blocks again on the channel send.

Finally the thread switches back to the left hand side as the Read operation has completed and data is available.

Gocon 2014 (36)

This slide shows the low level runtime.Syscall function which is the base for all functions in the os package.

Any time your code results in a call to the operating system, it will go through this function.

The call to entersyscall informs the runtime that this thread is about to block.

This allows the runtime to spin up a new thread which will service other goroutines while this current thread blocked.

This results in relatively few operating system threads per Go process, with the Go runtime taking care of assigning a runnable Goroutine to a free operating system thread.

Gocon 2014 (37)

In the previous section I discussed how goroutines reduce the overhead of managing many, sometimes hundreds of thousands of concurrent threads of execution.

There is another side to the goroutine story, and that is stack management, which leads me to my final topic.

Gocon 2014 (39)

This is a diagram of the memory layout of a process. The key thing we are interested is the location of the heap and the stack.

Traditionally inside the address space of a process, the heap is at the bottom of memory, just above the program (text) and grows upwards.

The stack is located at the top of the virtual address space, and grows downwards.

Gocon 2014 (40)

Because the heap and stack overwriting each other would be catastrophic, the operating system usually arranges to place an area of unwritable memory between the stack and the heap to ensure that if they did collide, the program will abort.

This is called a guard page, and effectively limits the stack size of a process, usually in the order of several megabytes.

Gocon 2014 (41)

We’ve discussed that threads share the same address space, so for each thread, it must have its own stack.

Because it is hard to predict the stack requirements of a particular thread, a large amount of memory is reserved for each thread’s stack along with a guard page.

The hope is that this is more than will ever be needed and the guard page will never be hit.

The downside is that as the number of threads in your program increases, the amount of available address space is reduced.

Gocon 2014 (42)

We’ve seen that the Go runtime schedules a large number of goroutines onto a small number of threads, but what about the stack requirements of those goroutines ?

Instead of using guard pages, the Go compiler inserts a check as part of every function call to check if there is sufficient stack for the function to run. If there is not, the runtime can allocate more stack space.

Because of this check, a goroutines initial stack can be made much smaller, which in turn permits Go programmers to treat goroutines as cheap resources.

Gocon 2014 (43)

This is a slide that shows how stacks are managed in Go 1.2.

When G calls to H there is not enough space for H to run, so the runtime allocates a new stack frame from the heap, then runs H on that new stack segment. When H returns, the stack area is returned to the heap before returning to G.

Gocon 2014 (44)

This method of managing the stack works well in general, but for certain types of code, usually recursive code, it can cause the inner loop of your program to straddle one of these stack boundaries.

For example, in the inner loop of your program, function G may call H many times in a loop,

Each time this will cause a stack split. This is known as the hot split problem.

Gocon 2014 (45)

To solve hot splits, Go 1.3 has adopted a new stack management method.

Instead of adding and removing additional stack segments, if the stack of a goroutine is too small, a new, larger, stack will be allocated.

The old stack’s contents are copied to the new stack, then the goroutine continues with its new larger stack.

After the first call to H the stack will be large enough that the check for available stack space will always succeed.

This resolves the hot split problem.

Gocon 2014 (46)

Values, Inlining, Escape Analysis, Goroutines, and segmented/copying stacks.

These are the five features that I chose to speak about today, but they are by no means the only things that makes Go a fast programming language, just as there more that three reasons that people cite as their reason to learn Go.

As powerful as these five features are individually, they do not exist in isolation.

For example, the way the runtime multiplexes goroutines onto threads would not be nearly as efficient without growable stacks.

Inlining reduces the cost of the stack size check by combining smaller functions into larger ones.

Escape analysis reduces the pressure on the garbage collector by automatically moving allocations from the heap to the stack.

Escape analysis is also provides better cache locality.

Without growable stacks, escape analysis might place too much pressure on the stack.

Gocon 2014 (47)

* Thank you to the Gocon organisers for permitting me to speak today
* twitter / web / email details
* thanks to @offbymany, @billkennedy_go, and Minux for their assistance in preparing this talk.

autobench-next updated for Go 1.3

Now that go1.3beta1 has been released I’ve updated the autobench-next branch to track Go 1.2 vs tip (go1.3beta1).

Using autobench is very simple, clone the repository and run make to produce a benchmark on your machine.

% cd devel
% git clone -b autobench-next https://github.com/davecheney/autobench.git
% cd autobench
% make

You can stay up to date with the update target

% git pull 
% make update
% make

Contributions and benchmark results are always welcome. As the Go 1.3 cycle draws to a close I will merge this branch back into master replacing the older 1.1 vs 1.2 comparisons.

Introducing autobench-next

Earlier this year I wrote a small harness to compare the relative performance of Go 1.0 and the then just released Go 1.1. You can read the posts about the Go 1.1 performance improvements: amd64, 386 and arm.

As the Go 1.2 cycle is entering feature freeze next week, I’ve taken the opportunity to create a new branch of autobench, autobench-next which tracks Go 1.1 vs tip.

Using autobench is very simple, clone the repository and run make to produce a benchmark on your machine.

% cd devel
% git clone -b autobench-next https://github.com/davecheney/autobench.git
% cd autobench
% make

You can stay up to date with the update target

% make update
% make

Contributions and benchmark results are always welcome. As the Go 1.2 cycle draws to a close I will merge this branch back into master replacing the older 1.0 vs 1.1 comparisons.