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When generating long strings or slices with Repeat we currently reuse intermediate states as a way to quickly build exponentially longer results. This works well as long as the intermediate states fit into the processor D-cache. If they don't we start thrashing the D-cache by reading in the whole intermediate state over and over on each iteration. Instead, once we reach a large enough intermediate state (that allows the memcpy operation to perform at peak) we cap the size of chunk of the state that is used as source for subsequent appends. This ensures that this smaller source chunk is always present in the D-cache, and the append operation does not need to read the state contents from memory. Currently the cap is set to 8KB, a number derived via experimentation to yield the highest performance across a a large range of result sizes. Slightly higher caps also produced similar results: 8KB was chosen as the smallest one in this performance plateau with the intention to minimize D-cache pollution. For result sizes larger than the fastest cache levels we get significantly higher performance compared to the current implementation: strings: name old speed new speed delta RepeatLarge/256/1-16 1.73GB/s ± 1% 1.73GB/s ± 0% ~ (p=0.556 n=5+4) RepeatLarge/256/16-16 2.02GB/s ± 0% 1.95GB/s ± 8% ~ (p=0.222 n=5+5) RepeatLarge/512/1-16 2.30GB/s ±13% 2.47GB/s ± 1% ~ (p=0.548 n=5+5) RepeatLarge/512/16-16 2.38GB/s ±16% 2.77GB/s ± 1% +16.27% (p=0.032 n=5+5) RepeatLarge/1024/1-16 3.17GB/s ± 1% 3.18GB/s ± 0% ~ (p=0.730 n=4+5) RepeatLarge/1024/16-16 3.39GB/s ± 2% 3.38GB/s ± 1% ~ (p=0.548 n=5+5) RepeatLarge/2048/1-16 3.32GB/s ± 2% 3.32GB/s ± 2% ~ (p=1.000 n=5+5) RepeatLarge/2048/16-16 3.41GB/s ± 4% 3.46GB/s ± 2% ~ (p=0.310 n=5+5) RepeatLarge/4096/1-16 3.60GB/s ± 4% 3.67GB/s ± 3% ~ (p=0.690 n=5+5) RepeatLarge/4096/16-16 3.74GB/s ± 3% 3.71GB/s ± 5% ~ (p=0.690 n=5+5) RepeatLarge/8192/1-16 3.94GB/s ± 4% 4.01GB/s ± 1% ~ (p=0.222 n=5+5) RepeatLarge/8192/16-16 3.94GB/s ± 6% 4.05GB/s ± 1% ~ (p=0.222 n=5+5) RepeatLarge/8192/4097-16 4.25GB/s ± 6% 4.32GB/s ± 3% ~ (p=0.690 n=5+5) RepeatLarge/16384/1-16 4.96GB/s ± 1% 5.02GB/s ± 2% ~ (p=0.421 n=5+5) RepeatLarge/16384/16-16 4.99GB/s ± 2% 5.07GB/s ± 1% ~ (p=0.421 n=5+5) RepeatLarge/16384/4097-16 5.15GB/s ± 3% 5.17GB/s ± 1% ~ (p=1.000 n=5+5) RepeatLarge/32768/1-16 5.44GB/s ± 2% 5.42GB/s ± 1% ~ (p=0.841 n=5+5) RepeatLarge/32768/16-16 5.46GB/s ± 4% 5.44GB/s ± 1% ~ (p=0.905 n=5+4) RepeatLarge/32768/4097-16 4.84GB/s ± 2% 4.59GB/s ±12% -5.05% (p=0.032 n=5+5) RepeatLarge/65536/1-16 5.85GB/s ± 0% 5.84GB/s ± 1% ~ (p=0.690 n=5+5) RepeatLarge/65536/16-16 5.81GB/s ± 2% 5.84GB/s ± 2% ~ (p=0.421 n=5+5) RepeatLarge/65536/4097-16 5.38GB/s ± 6% 5.45GB/s ± 1% ~ (p=1.000 n=5+5) RepeatLarge/131072/1-16 6.20GB/s ± 1% 6.31GB/s ± 1% +1.80% (p=0.008 n=5+5) RepeatLarge/131072/16-16 6.12GB/s ± 3% 6.25GB/s ± 3% ~ (p=0.095 n=5+5) RepeatLarge/131072/4097-16 5.95GB/s ± 1% 5.85GB/s ±10% ~ (p=1.000 n=5+5) RepeatLarge/262144/1-16 6.33GB/s ± 1% 6.56GB/s ± 0% +3.62% (p=0.016 n=5+4) RepeatLarge/262144/16-16 6.42GB/s ± 0% 6.65GB/s ± 1% +3.58% (p=0.016 n=4+5) RepeatLarge/262144/4097-16 6.31GB/s ± 1% 6.44GB/s ± 1% +1.94% (p=0.008 n=5+5) RepeatLarge/524288/1-16 6.23GB/s ± 1% 6.92GB/s ± 3% +11.02% (p=0.008 n=5+5) RepeatLarge/524288/16-16 6.24GB/s ± 1% 6.97GB/s ± 2% +11.77% (p=0.016 n=4+5) RepeatLarge/524288/4097-16 6.14GB/s ± 2% 6.73GB/s ± 3% +9.50% (p=0.008 n=5+5) RepeatLarge/1048576/1-16 5.23GB/s ± 1% 6.53GB/s ± 6% +24.85% (p=0.008 n=5+5) RepeatLarge/1048576/16-16 5.21GB/s ± 1% 6.56GB/s ± 4% +25.93% (p=0.008 n=5+5) RepeatLarge/1048576/4097-16 5.22GB/s ± 1% 6.26GB/s ± 2% +20.09% (p=0.008 n=5+5) RepeatLarge/2097152/1-16 3.95GB/s ± 1% 5.96GB/s ± 1% +51.01% (p=0.008 n=5+5) RepeatLarge/2097152/16-16 3.94GB/s ± 1% 5.98GB/s ± 2% +51.99% (p=0.008 n=5+5) RepeatLarge/2097152/4097-16 4.94GB/s ± 1% 5.71GB/s ± 2% +15.63% (p=0.008 n=5+5) RepeatLarge/4194304/1-16 3.10GB/s ± 1% 5.89GB/s ± 1% +89.90% (p=0.008 n=5+5) RepeatLarge/4194304/16-16 3.09GB/s ± 1% 5.86GB/s ± 1% +89.89% (p=0.008 n=5+5) RepeatLarge/4194304/4097-16 3.13GB/s ± 1% 5.89GB/s ± 1% +88.36% (p=0.008 n=5+5) RepeatLarge/8388608/1-16 3.06GB/s ± 1% 6.31GB/s ±16% +105.84% (p=0.008 n=5+5) RepeatLarge/8388608/16-16 3.08GB/s ± 1% 6.62GB/s ± 1% +114.66% (p=0.008 n=5+5) RepeatLarge/8388608/4097-16 3.13GB/s ± 2% 6.87GB/s ± 1% +119.62% (p=0.008 n=5+5) RepeatLarge/16777216/1-16 3.21GB/s ± 3% 5.88GB/s ± 1% +83.27% (p=0.008 n=5+5) RepeatLarge/16777216/16-16 3.23GB/s ± 2% 5.84GB/s ± 2% +80.49% (p=0.008 n=5+5) RepeatLarge/16777216/4097-16 3.30GB/s ± 6% 5.88GB/s ± 2% +78.18% (p=0.008 n=5+5) RepeatLarge/33554432/1-16 3.71GB/s ± 3% 5.91GB/s ± 2% +59.17% (p=0.008 n=5+5) RepeatLarge/33554432/16-16 3.67GB/s ± 3% 5.91GB/s ± 2% +61.13% (p=0.008 n=5+5) RepeatLarge/33554432/4097-16 3.71GB/s ± 1% 5.77GB/s ± 6% +55.51% (p=0.008 n=5+5) RepeatLarge/67108864/1-16 4.61GB/s ±11% 6.00GB/s ± 5% +30.15% (p=0.008 n=5+5) RepeatLarge/67108864/16-16 4.62GB/s ± 7% 6.11GB/s ± 2% +32.35% (p=0.008 n=5+5) RepeatLarge/67108864/4097-16 4.71GB/s ± 2% 6.24GB/s ± 2% +32.60% (p=0.008 n=5+5) RepeatLarge/134217728/1-16 4.53GB/s ± 8% 6.28GB/s ±11% +38.57% (p=0.008 n=5+5) RepeatLarge/134217728/16-16 4.78GB/s ± 3% 6.36GB/s ± 3% +33.16% (p=0.008 n=5+5) RepeatLarge/134217728/4097-16 4.73GB/s ± 6% 6.46GB/s ± 3% +36.63% (p=0.008 n=5+5) RepeatLarge/268435456/1-16 4.09GB/s ±25% 6.37GB/s ±19% +56.00% (p=0.008 n=5+5) RepeatLarge/268435456/16-16 4.50GB/s ± 4% 6.86GB/s ± 0% +52.49% (p=0.016 n=5+4) RepeatLarge/268435456/4097-16 4.73GB/s ± 5% 6.90GB/s ± 0% +45.94% (p=0.008 n=5+5) RepeatLarge/536870912/1-16 4.38GB/s ±36% 6.52GB/s ± 8% +48.68% (p=0.008 n=5+5) RepeatLarge/536870912/16-16 4.69GB/s ±12% 6.90GB/s ± 1% +46.97% (p=0.008 n=5+5) RepeatLarge/536870912/4097-16 4.87GB/s ± 8% 6.98GB/s ± 0% +43.36% (p=0.008 n=5+5) RepeatLarge/1073741824/1-16 3.87GB/s ±28% 6.96GB/s ± 1% +79.94% (p=0.016 n=5+4) RepeatLarge/1073741824/16-16 4.79GB/s ± 9% 6.93GB/s ± 0% +44.79% (p=0.008 n=5+5) RepeatLarge/1073741824/4097-16 4.65GB/s ± 8% 7.02GB/s ± 1% +51.02% (p=0.008 n=5+5) bytes: name old speed new speed delta RepeatLarge/256/1-16 1.93GB/s ± 1% 1.84GB/s ± 1% -4.81% (p=0.000 n=10+10) RepeatLarge/256/16-16 2.25GB/s ± 2% 2.15GB/s ± 1% -4.45% (p=0.000 n=9+8) RepeatLarge/512/1-16 2.71GB/s ± 1% 2.62GB/s ± 1% -3.27% (p=0.000 n=10+9) RepeatLarge/512/16-16 2.96GB/s ± 4% 2.91GB/s ± 1% ~ (p=0.243 n=9+10) RepeatLarge/1024/1-16 3.35GB/s ± 1% 3.27GB/s ± 1% -2.61% (p=0.000 n=9+10) RepeatLarge/1024/16-16 3.56GB/s ± 2% 3.52GB/s ± 1% -1.10% (p=0.010 n=10+9) RepeatLarge/2048/1-16 3.52GB/s ± 1% 3.45GB/s ± 1% -1.92% (p=0.000 n=10+10) RepeatLarge/2048/16-16 3.61GB/s ± 1% 3.58GB/s ± 0% -0.82% (p=0.008 n=9+8) RepeatLarge/4096/1-16 3.85GB/s ± 2% 3.80GB/s ± 2% ~ (p=0.165 n=10+10) RepeatLarge/4096/16-16 3.88GB/s ± 3% 3.84GB/s ± 4% ~ (p=0.393 n=10+10) RepeatLarge/8192/1-16 4.12GB/s ± 2% 4.04GB/s ± 1% -1.96% (p=0.000 n=10+10) RepeatLarge/8192/16-16 4.11GB/s ± 2% 4.09GB/s ± 1% ~ (p=0.278 n=9+10) RepeatLarge/8192/4097-16 4.38GB/s ± 1% 4.39GB/s ± 4% ~ (p=0.720 n=9+10) RepeatLarge/16384/1-16 5.06GB/s ± 2% 4.95GB/s ± 3% -2.29% (p=0.001 n=10+9) RepeatLarge/16384/16-16 5.11GB/s ± 3% 5.06GB/s ± 3% ~ (p=0.315 n=10+9) RepeatLarge/16384/4097-16 5.22GB/s ± 3% 5.26GB/s ± 3% ~ (p=0.211 n=9+10) RepeatLarge/32768/1-16 5.54GB/s ± 2% 5.50GB/s ± 3% ~ (p=0.353 n=10+10) RepeatLarge/32768/16-16 5.55GB/s ± 1% 5.60GB/s ± 1% +0.91% (p=0.035 n=10+9) RepeatLarge/32768/4097-16 4.88GB/s ± 2% 4.85GB/s ± 2% ~ (p=0.447 n=10+9) RepeatLarge/65536/1-16 5.86GB/s ± 1% 5.93GB/s ± 2% +1.18% (p=0.043 n=8+10) RepeatLarge/65536/16-16 5.83GB/s ± 2% 5.98GB/s ± 1% +2.67% (p=0.000 n=10+10) RepeatLarge/65536/4097-16 5.57GB/s ± 0% 5.56GB/s ± 3% ~ (p=0.696 n=8+10) RepeatLarge/131072/1-16 6.23GB/s ± 1% 6.38GB/s ± 2% +2.51% (p=0.000 n=9+10) RepeatLarge/131072/16-16 6.21GB/s ± 2% 6.37GB/s ± 1% +2.72% (p=0.000 n=9+10) RepeatLarge/131072/4097-16 6.04GB/s ± 1% 6.09GB/s ± 3% ~ (p=0.356 n=9+10) RepeatLarge/262144/1-16 6.47GB/s ± 1% 6.63GB/s ± 2% +2.57% (p=0.003 n=10+10) RepeatLarge/262144/16-16 6.45GB/s ± 2% 6.69GB/s ± 2% +3.65% (p=0.000 n=10+10) RepeatLarge/262144/4097-16 6.35GB/s ± 1% 6.51GB/s ± 2% +2.48% (p=0.000 n=9+10) RepeatLarge/524288/1-16 6.21GB/s ± 2% 6.95GB/s ± 1% +11.95% (p=0.000 n=10+10) RepeatLarge/524288/16-16 6.24GB/s ± 2% 6.93GB/s ± 2% +11.11% (p=0.000 n=10+10) RepeatLarge/524288/4097-16 6.18GB/s ± 2% 6.82GB/s ± 1% +10.39% (p=0.000 n=9+10) RepeatLarge/1048576/1-16 5.34GB/s ± 2% 6.41GB/s ± 2% +20.05% (p=0.000 n=10+10) RepeatLarge/1048576/16-16 5.33GB/s ± 1% 6.45GB/s ± 2% +20.84% (p=0.000 n=10+9) RepeatLarge/1048576/4097-16 5.28GB/s ± 1% 6.17GB/s ± 2% +16.75% (p=0.000 n=10+10) RepeatLarge/2097152/1-16 4.04GB/s ± 1% 6.21GB/s ± 1% +53.89% (p=0.000 n=9+8) RepeatLarge/2097152/16-16 4.02GB/s ± 1% 6.20GB/s ± 2% +54.37% (p=0.000 n=10+9) RepeatLarge/2097152/4097-16 4.94GB/s ± 1% 6.04GB/s ± 1% +22.36% (p=0.000 n=10+10) RepeatLarge/4194304/1-16 3.10GB/s ± 1% 5.74GB/s ± 0% +85.04% (p=0.000 n=10+9) RepeatLarge/4194304/16-16 3.10GB/s ± 2% 5.72GB/s ± 1% +84.26% (p=0.000 n=9+10) RepeatLarge/4194304/4097-16 3.03GB/s ± 4% 5.61GB/s ± 1% +85.06% (p=0.000 n=10+9) RepeatLarge/8388608/1-16 3.08GB/s ± 2% 6.25GB/s ± 1% +103.09% (p=0.000 n=9+9) RepeatLarge/8388608/16-16 3.07GB/s ± 2% 6.26GB/s ± 3% +104.07% (p=0.000 n=10+9) RepeatLarge/8388608/4097-16 3.08GB/s ± 2% 6.23GB/s ± 2% +102.09% (p=0.000 n=9+10) RepeatLarge/16777216/1-16 3.25GB/s ± 2% 5.78GB/s ± 3% +78.03% (p=0.000 n=9+9) RepeatLarge/16777216/16-16 3.25GB/s ± 1% 5.75GB/s ± 1% +77.21% (p=0.000 n=9+10) RepeatLarge/16777216/4097-16 3.29GB/s ± 3% 5.72GB/s ± 2% +73.74% (p=0.000 n=10+10) RepeatLarge/33554432/1-16 3.68GB/s ± 2% 5.90GB/s ± 1% +60.20% (p=0.000 n=10+10) RepeatLarge/33554432/16-16 3.69GB/s ± 3% 5.88GB/s ± 1% +59.54% (p=0.000 n=10+9) RepeatLarge/33554432/4097-16 3.74GB/s ± 1% 5.94GB/s ± 2% +58.68% (p=0.000 n=7+10) RepeatLarge/67108864/1-16 4.62GB/s ±12% 6.11GB/s ± 3% +32.23% (p=0.000 n=10+9) RepeatLarge/67108864/16-16 4.77GB/s ± 2% 6.09GB/s ± 2% +27.88% (p=0.000 n=9+9) RepeatLarge/67108864/4097-16 4.78GB/s ± 1% 6.19GB/s ± 1% +29.51% (p=0.000 n=9+10) RepeatLarge/134217728/1-16 4.60GB/s ±16% 6.52GB/s ± 9% +41.67% (p=0.000 n=10+10) RepeatLarge/134217728/16-16 4.80GB/s ± 4% 6.81GB/s ± 2% +41.82% (p=0.000 n=10+9) RepeatLarge/134217728/4097-16 4.79GB/s ± 4% 6.81GB/s ± 2% +42.31% (p=0.000 n=9+10) RepeatLarge/268435456/1-16 4.43GB/s ±25% 6.27GB/s ±14% +41.52% (p=0.000 n=10+10) RepeatLarge/268435456/16-16 4.75GB/s ± 4% 6.68GB/s ± 4% +40.50% (p=0.000 n=9+10) RepeatLarge/268435456/4097-16 4.75GB/s ± 3% 6.58GB/s ± 4% +38.68% (p=0.000 n=9+10) RepeatLarge/536870912/1-16 4.96GB/s ± 9% 6.39GB/s ±16% +28.90% (p=0.000 n=8+10) RepeatLarge/536870912/16-16 4.66GB/s ± 6% 6.57GB/s ± 7% +40.82% (p=0.000 n=10+9) RepeatLarge/536870912/4097-16 4.68GB/s ±11% 6.88GB/s ± 3% +47.01% (p=0.000 n=10+9) RepeatLarge/1073741824/1-16 4.39GB/s ±23% 6.57GB/s ± 5% +49.75% (p=0.000 n=10+8) RepeatLarge/1073741824/16-16 4.73GB/s ±13% 6.89GB/s ± 1% +45.68% (p=0.000 n=9+8) RepeatLarge/1073741824/4097-16 4.97GB/s ±15% 6.73GB/s ± 9% +35.45% (p=0.000 n=10+10) The results above come from a Intel i9-9980HK (256KB L2) with TurboBoost disabled. Change-Id: I79dd57da0429aee9020ffd7bc458a034b999b740 Reviewed-on: https://go-review.googlesource.com/c/go/+/419054 Reviewed-by: Ian Lance Taylor <iant@google.com> Auto-Submit: Ian Lance Taylor <iant@google.com> Run-TryBot: Ian Lance Taylor <iant@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> |
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| CONTRIBUTING.md | ||
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