71 lines
4.6 KiB
Markdown
71 lines
4.6 KiB
Markdown
A data structure for optimistic concurrency control on ranges of bitwise-lexicographically-ordered keys.
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Intended as an alternative to FoundationDB's skip list.
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Hardware for all benchmarks is an AMD Ryzen 9 7900 with (2x32GB) 5600MT/s CL28-34-34-89 1.35V RAM.
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```
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$ clang++ --version
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Ubuntu clang version 21.1.8 (6ubuntu1)
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Target: x86_64-pc-linux-gnu
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Thread model: posix
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InstalledDir: /usr/lib/llvm-21/bin
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```
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# Microbenchmark
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## Skip list
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| ns/op | op/s | err% | ins/op | cyc/op | IPC | bra/op | miss% | total | benchmark
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|--------------------:|--------------------:|--------:|----------------:|----------------:|-------:|---------------:|--------:|----------:|:----------
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| 164.29 | 6,086,873.38 | 0.0% | 3,107.03 | 604.19 | 5.142 | 558.59 | 0.0% | 1.96 | `point reads`
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| 161.05 | 6,209,395.38 | 0.1% | 3,036.76 | 592.21 | 5.128 | 539.35 | 0.0% | 1.93 | `prefix reads`
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| 239.55 | 4,174,539.38 | 0.1% | 3,722.71 | 880.68 | 4.227 | 692.00 | 0.0% | 2.86 | `range reads`
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| 354.75 | 2,818,919.14 | 0.7% | 4,523.64 | 1,304.75 | 3.467 | 720.22 | 2.0% | 4.23 | `point writes`
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| 345.32 | 2,895,878.47 | 0.1% | 4,484.57 | 1,270.31 | 3.530 | 705.00 | 1.8% | 4.12 | `prefix writes`
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| 193.48 | 5,168,547.42 | 0.1% | 2,224.10 | 711.72 | 3.125 | 377.17 | 3.3% | 2.32 | `range writes`
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| 404.89 | 2,469,777.50 | 2.4% | 6,855.96 | 1,489.70 | 4.602 | 1,227.82 | 1.3% | 0.05 | `monotonic increasing point writes`
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| 134,231.80 | 7,449.80 | 1.9% | 812,045.25 | 495,770.40 | 1.638 | 151,246.50 | 0.9% | 0.01 | `worst case for radix tree`
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| 37.80 | 26,454,311.17 | 0.4% | 701.00 | 139.14 | 5.038 | 102.00 | 0.0% | 0.01 | `create and destroy`
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## Radix tree (this implementation)
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| ns/op | op/s | err% | ins/op | cyc/op | IPC | bra/op | miss% | total | benchmark
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|--------------------:|--------------------:|--------:|----------------:|----------------:|-------:|---------------:|--------:|----------:|:----------
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| 12.89 | 77,565,115.56 | 0.1% | 244.55 | 47.43 | 5.155 | 34.21 | 0.6% | 0.15 | `point reads`
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| 15.11 | 66,162,047.76 | 0.1% | 297.79 | 55.60 | 5.356 | 43.23 | 0.4% | 0.18 | `prefix reads`
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| 36.29 | 27,559,358.29 | 0.1% | 783.16 | 133.44 | 5.869 | 109.52 | 0.2% | 0.43 | `range reads`
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| 20.53 | 48,719,405.55 | 0.1% | 381.81 | 75.51 | 5.057 | 51.04 | 0.5% | 0.25 | `point writes`
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| 39.37 | 25,402,042.40 | 0.1% | 685.00 | 144.83 | 4.730 | 106.72 | 0.3% | 0.47 | `prefix writes`
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| 43.78 | 22,843,841.63 | 0.1% | 800.40 | 161.06 | 4.970 | 127.36 | 0.1% | 0.53 | `range writes`
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| 78.37 | 12,760,008.75 | 1.0% | 1,452.61 | 288.24 | 5.040 | 278.69 | 0.1% | 0.01 | `monotonic increasing point writes`
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| 322,885.50 | 3,097.07 | 1.5% | 4,362,382.00 | 1,183,852.00 | 3.685 | 765,301.00 | 0.1% | 0.01 | `worst case for radix tree`
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| 99.99 | 10,000,718.79 | 0.4% | 1,775.00 | 367.93 | 4.824 | 288.00 | 0.0% | 0.01 | `create and destroy`
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# "Real data" test
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Point queries only. Gc ratio is the ratio of time spent doing garbage collection to time spent adding writes or doing garbage collection. Lower is better.
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## skip list
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```
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Check: 4.62967 seconds, 352.195 MB/s, Add: 3.34177 seconds, 167.771 MB/s, Gc ratio: 37.9399%, Peak idle memory: 5.51852e+06
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```
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## radix tree
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```
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Check: 1.00477 seconds, 1622.8 MB/s, Add: 1.21142 seconds, 462.808 MB/s, Gc ratio: 39.4716%, Peak idle memory: 2.0226e+06
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```
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## hash table
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(The hash table implementation doesn't work on range queries, and its purpose is to provide an idea of how fast point queries can be)
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```
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Check: 0.854254 seconds, 1908.74 MB/s, Add: 0.632626 seconds, 886.232 MB/s, Gc ratio: 41.0827%, Peak idle memory: 0
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```
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