2 Commits

Author	SHA1	Message	Date
Russ Cox	d447279927	cmd/internal/gc: optimize slice + write barrier ... The code generated for a slice x[i:j] or x[i:j:k] computes the entire new slice (base, len, cap) and then uses it as the evaluation of the slice expression. If the slice is part of an update x = x[i:j] or x = x[i:j:k], there are opportunities to avoid computing some of these fields. For x = x[0:i], we know that only the len is changing; base can be ignored completely, and cap can be left unmodified. For x = x[0:i:j], we know that only len and cap are changing; base can be ignored completely. For x = x[i:i], we know that the resulting cap is zero, and we don't adjust the base during a slice producing a zero-cap result, so again base can be ignored completely. No write to base, no write barrier. The old slice code was trying to work at a Go syntax level, mainly because that was how you wrote code just once instead of once per architecture. Now the compiler is factored a bit better and we can implement slice during code generation but still have one copy of the code. So the new code is working at that lower level. (It must, to update only parts of the result.) This CL by itself: name old mean new mean delta BinaryTree17 5.81s × (0.98,1.03) 5.71s × (0.96,1.05) ~ (p=0.101) Fannkuch11 4.35s × (1.00,1.00) 4.39s × (1.00,1.00) +0.79% (p=0.000) FmtFprintfEmpty 86.0ns × (0.94,1.11) 82.6ns × (0.98,1.04) -3.86% (p=0.048) FmtFprintfString 276ns × (0.98,1.04) 273ns × (0.98,1.02) ~ (p=0.235) FmtFprintfInt 274ns × (0.98,1.06) 270ns × (0.99,1.01) ~ (p=0.119) FmtFprintfIntInt 506ns × (0.99,1.01) 475ns × (0.99,1.01) -6.02% (p=0.000) FmtFprintfPrefixedInt 391ns × (0.99,1.01) 393ns × (1.00,1.01) ~ (p=0.139) FmtFprintfFloat 566ns × (0.99,1.01) 574ns × (1.00,1.01) +1.33% (p=0.001) FmtManyArgs 1.91µs × (0.99,1.01) 1.87µs × (0.99,1.02) -1.83% (p=0.000) GobDecode 15.3ms × (0.99,1.02) 15.0ms × (0.98,1.05) -1.84% (p=0.042) GobEncode 11.5ms × (0.97,1.03) 11.4ms × (0.99,1.03) ~ (p=0.152) Gzip 645ms × (0.99,1.01) 647ms × (0.99,1.01) ~ (p=0.265) Gunzip 142ms × (1.00,1.00) 143ms × (1.00,1.01) +0.90% (p=0.000) HTTPClientServer 90.5µs × (0.97,1.04) 88.5µs × (0.99,1.03) -2.27% (p=0.014) JSONEncode 32.0ms × (0.98,1.03) 29.6ms × (0.98,1.01) -7.51% (p=0.000) JSONDecode 114ms × (0.99,1.01) 104ms × (1.00,1.01) -8.60% (p=0.000) Mandelbrot200 6.04ms × (1.00,1.01) 6.02ms × (1.00,1.00) ~ (p=0.057) GoParse 6.47ms × (0.97,1.05) 6.37ms × (0.97,1.04) ~ (p=0.105) RegexpMatchEasy0_32 171ns × (0.93,1.07) 152ns × (0.99,1.01) -11.09% (p=0.000) RegexpMatchEasy0_1K 550ns × (0.98,1.01) 530ns × (1.00,1.00) -3.78% (p=0.000) RegexpMatchEasy1_32 135ns × (0.99,1.02) 134ns × (0.99,1.01) -1.33% (p=0.002) RegexpMatchEasy1_1K 879ns × (1.00,1.01) 865ns × (1.00,1.00) -1.58% (p=0.000) RegexpMatchMedium_32 243ns × (1.00,1.00) 233ns × (1.00,1.00) -4.30% (p=0.000) RegexpMatchMedium_1K 70.3µs × (1.00,1.00) 69.5µs × (1.00,1.00) -1.13% (p=0.000) RegexpMatchHard_32 3.82µs × (1.00,1.01) 3.74µs × (1.00,1.00) -1.95% (p=0.000) RegexpMatchHard_1K 117µs × (1.00,1.00) 115µs × (1.00,1.00) -1.69% (p=0.000) Revcomp 917ms × (0.97,1.04) 920ms × (0.97,1.04) ~ (p=0.786) Template 114ms × (0.99,1.01) 117ms × (0.99,1.01) +2.58% (p=0.000) TimeParse 622ns × (0.99,1.01) 615ns × (0.99,1.00) -1.06% (p=0.000) TimeFormat 665ns × (0.99,1.01) 654ns × (0.99,1.00) -1.70% (p=0.000) This CL and previous CL (append) combined: name old mean new mean delta BinaryTree17 5.68s × (0.97,1.04) 5.71s × (0.96,1.05) ~ (p=0.638) Fannkuch11 4.41s × (0.98,1.03) 4.39s × (1.00,1.00) ~ (p=0.474) FmtFprintfEmpty 92.7ns × (0.91,1.16) 82.6ns × (0.98,1.04) -10.89% (p=0.004) FmtFprintfString 281ns × (0.96,1.08) 273ns × (0.98,1.02) ~ (p=0.078) FmtFprintfInt 288ns × (0.97,1.06) 270ns × (0.99,1.01) -6.37% (p=0.000) FmtFprintfIntInt 493ns × (0.97,1.04) 475ns × (0.99,1.01) -3.53% (p=0.002) FmtFprintfPrefixedInt 423ns × (0.97,1.04) 393ns × (1.00,1.01) -7.07% (p=0.000) FmtFprintfFloat 598ns × (0.99,1.01) 574ns × (1.00,1.01) -4.02% (p=0.000) FmtManyArgs 1.89µs × (0.98,1.05) 1.87µs × (0.99,1.02) ~ (p=0.305) GobDecode 14.8ms × (0.98,1.03) 15.0ms × (0.98,1.05) ~ (p=0.237) GobEncode 12.3ms × (0.98,1.01) 11.4ms × (0.99,1.03) -6.95% (p=0.000) Gzip 656ms × (0.99,1.05) 647ms × (0.99,1.01) ~ (p=0.101) Gunzip 142ms × (1.00,1.00) 143ms × (1.00,1.01) +0.58% (p=0.001) HTTPClientServer 91.2µs × (0.97,1.04) 88.5µs × (0.99,1.03) -3.02% (p=0.003) JSONEncode 32.6ms × (0.97,1.08) 29.6ms × (0.98,1.01) -9.10% (p=0.000) JSONDecode 114ms × (0.97,1.05) 104ms × (1.00,1.01) -8.74% (p=0.000) Mandelbrot200 6.11ms × (0.98,1.04) 6.02ms × (1.00,1.00) ~ (p=0.090) GoParse 6.66ms × (0.97,1.04) 6.37ms × (0.97,1.04) -4.41% (p=0.000) RegexpMatchEasy0_32 159ns × (0.99,1.00) 152ns × (0.99,1.01) -4.69% (p=0.000) RegexpMatchEasy0_1K 538ns × (1.00,1.01) 530ns × (1.00,1.00) -1.57% (p=0.000) RegexpMatchEasy1_32 138ns × (1.00,1.00) 134ns × (0.99,1.01) -2.91% (p=0.000) RegexpMatchEasy1_1K 869ns × (0.99,1.01) 865ns × (1.00,1.00) -0.51% (p=0.012) RegexpMatchMedium_32 252ns × (0.99,1.01) 233ns × (1.00,1.00) -7.85% (p=0.000) RegexpMatchMedium_1K 72.7µs × (1.00,1.00) 69.5µs × (1.00,1.00) -4.43% (p=0.000) RegexpMatchHard_32 3.85µs × (1.00,1.00) 3.74µs × (1.00,1.00) -2.74% (p=0.000) RegexpMatchHard_1K 118µs × (1.00,1.00) 115µs × (1.00,1.00) -2.24% (p=0.000) Revcomp 920ms × (0.97,1.07) 920ms × (0.97,1.04) ~ (p=0.998) Template 129ms × (0.98,1.03) 117ms × (0.99,1.01) -9.79% (p=0.000) TimeParse 619ns × (0.99,1.01) 615ns × (0.99,1.00) -0.57% (p=0.011) TimeFormat 661ns × (0.98,1.04) 654ns × (0.99,1.00) ~ (p=0.223) Change-Id: If054d81ab2c71d8d62cf54b5b1fac2af66b387fc Reviewed-on: https://go-review.googlesource.com/9813 Reviewed-by: David Chase <drchase@google.com> Run-TryBot: Russ Cox <rsc@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>	2015-05-13 19:20:39 +00:00
Russ Cox	8552047a32	cmd/internal/gc: optimize append + write barrier ... The code generated for x = append(x, v) is roughly: t := x if len(t)+1 > cap(t) { t = grow(t) } t[len(t)] = v len(t)++ x = t We used to generate this code as Go pseudocode during walk. Generate it instead as actual instructions during gen. Doing so lets us apply a few optimizations. The most important is that when, as in the above example, the source slice and the destination slice are the same, the code can instead do: t := x if len(t)+1 > cap(t) { t = grow(t) x = {base(t), len(t)+1, cap(t)} } else { len(x)++ } t[len(t)] = v That is, in the fast path that does not reallocate the array, only the updated length needs to be written back to x, not the array pointer and not the capacity. This is more like what you'd write by hand in C. It's faster in general, since the fast path elides two of the three stores, but it's especially faster when the form of x is such that the base pointer write would turn into a write barrier. No write, no barrier. name old mean new mean delta BinaryTree17 5.68s × (0.97,1.04) 5.81s × (0.98,1.03) +2.35% (p=0.023) Fannkuch11 4.41s × (0.98,1.03) 4.35s × (1.00,1.00) ~ (p=0.090) FmtFprintfEmpty 92.7ns × (0.91,1.16) 86.0ns × (0.94,1.11) -7.31% (p=0.038) FmtFprintfString 281ns × (0.96,1.08) 276ns × (0.98,1.04) ~ (p=0.219) FmtFprintfInt 288ns × (0.97,1.06) 274ns × (0.98,1.06) -4.94% (p=0.002) FmtFprintfIntInt 493ns × (0.97,1.04) 506ns × (0.99,1.01) +2.65% (p=0.009) FmtFprintfPrefixedInt 423ns × (0.97,1.04) 391ns × (0.99,1.01) -7.52% (p=0.000) FmtFprintfFloat 598ns × (0.99,1.01) 566ns × (0.99,1.01) -5.27% (p=0.000) FmtManyArgs 1.89µs × (0.98,1.05) 1.91µs × (0.99,1.01) ~ (p=0.231) GobDecode 14.8ms × (0.98,1.03) 15.3ms × (0.99,1.02) +3.01% (p=0.000) GobEncode 12.3ms × (0.98,1.01) 11.5ms × (0.97,1.03) -5.93% (p=0.000) Gzip 656ms × (0.99,1.05) 645ms × (0.99,1.01) ~ (p=0.055) Gunzip 142ms × (1.00,1.00) 142ms × (1.00,1.00) -0.32% (p=0.034) HTTPClientServer 91.2µs × (0.97,1.04) 90.5µs × (0.97,1.04) ~ (p=0.468) JSONEncode 32.6ms × (0.97,1.08) 32.0ms × (0.98,1.03) ~ (p=0.190) JSONDecode 114ms × (0.97,1.05) 114ms × (0.99,1.01) ~ (p=0.887) Mandelbrot200 6.11ms × (0.98,1.04) 6.04ms × (1.00,1.01) ~ (p=0.167) GoParse 6.66ms × (0.97,1.04) 6.47ms × (0.97,1.05) -2.81% (p=0.014) RegexpMatchEasy0_32 159ns × (0.99,1.00) 171ns × (0.93,1.07) +7.19% (p=0.002) RegexpMatchEasy0_1K 538ns × (1.00,1.01) 550ns × (0.98,1.01) +2.30% (p=0.000) RegexpMatchEasy1_32 138ns × (1.00,1.00) 135ns × (0.99,1.02) -1.60% (p=0.000) RegexpMatchEasy1_1K 869ns × (0.99,1.01) 879ns × (1.00,1.01) +1.08% (p=0.000) RegexpMatchMedium_32 252ns × (0.99,1.01) 243ns × (1.00,1.00) -3.71% (p=0.000) RegexpMatchMedium_1K 72.7µs × (1.00,1.00) 70.3µs × (1.00,1.00) -3.34% (p=0.000) RegexpMatchHard_32 3.85µs × (1.00,1.00) 3.82µs × (1.00,1.01) -0.81% (p=0.000) RegexpMatchHard_1K 118µs × (1.00,1.00) 117µs × (1.00,1.00) -0.56% (p=0.000) Revcomp 920ms × (0.97,1.07) 917ms × (0.97,1.04) ~ (p=0.808) Template 129ms × (0.98,1.03) 114ms × (0.99,1.01) -12.06% (p=0.000) TimeParse 619ns × (0.99,1.01) 622ns × (0.99,1.01) ~ (p=0.062) TimeFormat 661ns × (0.98,1.04) 665ns × (0.99,1.01) ~ (p=0.524) See next CL for combination with a similar optimization for slice. The benchmarks that are slower in this CL are still faster overall with the combination of the two. Change-Id: I2a7421658091b2488c64741b4db15ab6c3b4cb7e Reviewed-on: https://go-review.googlesource.com/9812 Reviewed-by: David Chase <drchase@google.com>	2015-05-12 17:55:09 +00:00