golang 1.8工具鏈改進

astaxie發表於2016-11-21
Golang

golang 1.8工具鏈改進

本文是關於1.8開發週期中Go工具鏈改進的進度報告。

現在已經是11月了，golang1.8只剩最後的幾個修改列表，剩餘的會移到1.9釋出，1.8版本於2017年2月釋出。

對於本系列的更多內容，請閱讀我上一篇關於9月份的Go 1.8工具鏈改進的文章，以及我在1.7版對Go工具鏈改進的文章。

更快編譯

自從2015年8月釋出的Go 1.5以來，編譯時間顯著長於Go 1.4。 解決這種緩慢的工作開始於Go 1.7，並且仍在進行。

Robert Griesemer和Matthew Dempsky致力於重寫一個更快的解析器，並刪除了許多從以前版本遺留的基於yacc的解析器繼承的包級別的變數。 這個解析器產生一個新的抽象語法樹，而編譯器的其餘部分需先前的yacc語法樹。 對於1.8，新的解析器必須將其輸出轉換為先前的語法樹，以供編譯器的其餘部分使用。 即使使用這個額外的轉換步驟，新的解析器也不比以前的版本慢，並且計劃在Go 1.9中刪除這個轉換過程。

Go 1.8的目標是比1.7平均減少15%的編譯時間。 與兩個月前報告的3-5％的改進相比，還需要作出更多努力。

注意：jujud，kube-controller-manager和gogs的基準指令碼線上。 請自己嘗試並報告您的發現。

程式碼生成提速

go1.7週期的主要特點是64位Intel的新SSA後端。 在Go 1.8中，SSA後端已經推廣到Go支援的所有其他架構，並且舊的後端程式碼已被刪除。

amd64憑藉是最受歡迎的生產架構，一直是新特性最快支援的。 正如我在幾個月前報導的，比較Go 1.8和Go 1.7在英特爾架構上的結果顯示，程式碼生成，轉義分析和對std庫的優化有很大改進。

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)

從切換到SSA後端的重大改進出現在非intel體系結構上。 這裡是Arm64的結果：

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)

只是重新編譯程式碼就能有相當大的改進。

Defer and cgo的提升

如果，在go1.8，根據一些基準測試顯示，Austin將使用延遲的開銷減少了一半。 即使defer是否可用於熱程式碼路徑的問題依然沒有完全解決，但是根據一些基準測試，在go1.8 Austin(開發者)將使用延遲的開銷減少了一半。

runtime包基準測試結果不太好。

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)

在最常見的情況下，defer提高了三分之一效能，其中語句關閉不超過一個單一的變數。

此外，David Crawshaw的一項優化降低了cgo程式碼路徑近一半的開銷。

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支援64位mips平臺，感謝Minux和Cherry的工作。 然而，卻不支援不那麼強大但豐富的32位mips平臺。 感謝弗拉基米爾·斯特凡諾維奇（Vladimir Stefanovic）的工作，Go 1.8將支援32位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

雖然有32位mips主機可能太小，無法在本地編譯Go程式，您可以隨時在您的開發工作站做linux / mips交叉編譯。

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