Inline storage for instance fields and frame locals

[Hirevo]

Currently (before this PR), in the bytecode interpreter, instance fields and frame locals are stored within vectors (as Vec<Value>).

This means that to reach them, one needs to first dereference two pointers.

In the example of a class instance (stored as SOMRef<Instance>), one needs to:

• dereference once to get to the instance struct.
• dereference again to get to the field value within the vector of fields.

Due to the vector being a separate allocation, it is very likely that this causes cache misses, slowing down the program.

This PR uses raw pointer arithmetic, a bit of unsafe, and coordination with the GC to allocate additional space right besides the class instance (or stack frame) to store the fields (or locals) into, rather than into a separate vector, and uses pointer offsets to implement accesses, hopefully improving locality and therefore improving cache hit rates.

Depends on #33.

[som-rs-benchmarker]

Here are the benchmark results for feat/inline-fields (commit: f17df09):

AST interpreter

+-----------------+----------------------------------------+---------------------------+
| Benchmark       | master (base)                          | feat/inline-fields (head) |
+-----------------+----------------------------------------+---------------------------+
| Bounce          | 191.37 ms ± 15.42 (172.72..222.50)     | 1.05x ± 0.10 (0.93..1.09) |
| BubbleSort      | 249.42 ms ± 12.09 (238.96..275.60)     | 0.99x ± 0.05 (0.95..1.01) |
| DeltaBlue       | 162.23 ms ± 17.85 (142.58..192.92)     | 1.10x ± 0.13 (1.01..1.14) |
| Dispatch        | 188.68 ms ± 17.95 (173.00..224.17)     | 1.09x ± 0.12 (0.99..1.16) |
| Fannkuch        | 120.60 ms ± 10.79 (112.11..139.36)     | 0.97x ± 0.11 (0.85..1.03) |
| Fibonacci       | 348.72 ms ± 10.75 (340.14..376.46)     | 0.94x ± 0.07 (0.81..1.01) |
| FieldLoop       | 314.12 ms ± 13.66 (301.09..345.94)     | 1.06x ± 0.05 (1.03..1.08) |
| GraphSearch     | 82.45 ms ± 7.89 (75.89..101.25)        | 1.04x ± 0.10 (0.97..1.09) |
| IntegerLoop     | 327.72 ms ± 37.34 (295.60..422.43)     | 1.07x ± 0.13 (1.01..1.13) |
| JsonSmall       | 184.87 ms ± 4.98 (178.46..194.98)      | 0.96x ± 0.06 (0.87..1.02) |
| List            | 221.42 ms ± 6.70 (211.53..234.01)      | 0.99x ± 0.05 (0.92..1.05) |
| Loop            | 419.24 ms ± 30.02 (386.30..472.87)     | 1.04x ± 0.09 (0.96..1.09) |
| Mandelbrot      | 247.61 ms ± 22.79 (232.95..308.84)     | 0.98x ± 0.10 (0.89..1.03) |
| NBody           | 194.21 ms ± 3.62 (189.57..199.52)      | 0.94x ± 0.07 (0.85..1.01) |
| PageRank        | 278.19 ms ± 11.07 (263.22..302.83)     | 0.99x ± 0.05 (0.93..1.03) |
| Permute         | 304.78 ms ± 22.92 (280.50..360.63)     | 1.08x ± 0.09 (0.98..1.12) |
| Queens          | 237.88 ms ± 30.12 (216.11..319.32)     | 1.05x ± 0.15 (0.88..1.12) |
| QuickSort       | 71.62 ms ± 2.22 (69.61..77.28)         | 0.98x ± 0.12 (0.81..1.07) |
| Recurse         | 271.86 ms ± 15.12 (248.81..301.77)     | 1.05x ± 0.07 (0.98..1.08) |
| Richards        | 3987.78 ms ± 116.71 (3883.22..4193.07) | 1.03x ± 0.04 (0.96..1.05) |
| Sieve           | 410.50 ms ± 22.74 (376.53..457.70)     | 1.04x ± 0.07 (0.97..1.09) |
| Storage         | 80.77 ms ± 1.85 (78.41..84.34)         | 0.93x ± 0.16 (0.67..1.06) |
| Sum             | 173.83 ms ± 22.03 (146.29..208.79)     | 1.11x ± 0.15 (1.03..1.18) |
| Towers          | 308.83 ms ± 23.34 (282.98..359.38)     | 0.99x ± 0.09 (0.88..1.05) |
| TreeSort        | 147.51 ms ± 5.01 (142.78..159.36)      | 0.97x ± 0.08 (0.85..1.04) |
| WhileLoop       | 340.21 ms ± 19.45 (318.81..381.32)     | 0.93x ± 0.07 (0.86..1.02) |
|                 |                                        |                           |
| Average Speedup |               (baseline)               | 1.01x ± 0.02 (0.93..1.11) |
+-----------------+----------------------------------------+---------------------------+

The raw ReBench data files are available for download here: baseline and head

Bytecode interpreter

The raw ReBench data files are available for download here: baseline and head

The benchmarks were run using ReBench v1.2.0
The statistical analysis was done using rebench-tabler v0.1.0

The source code of this benchmark runner is available as a GitHub Gist for more details about the setup

[som-rs-benchmarker]

Here are the benchmark results for feat/inline-fields (commit: 659a218):

AST interpreter

+-----------------+----------------------------------------+---------------------------+
| Benchmark       | master (base)                          | feat/inline-fields (head) |
+-----------------+----------------------------------------+---------------------------+
| Bounce          | 193.56 ms ± 6.78 (184.02..203.93)      | 0.89x ± 0.10 (0.78..0.99) |
| BubbleSort      | 274.03 ms ± 14.72 (252.09..293.55)     | 0.94x ± 0.14 (0.69..1.06) |
| DeltaBlue       | 170.21 ms ± 24.76 (149.46..227.88)     | 1.00x ± 0.18 (0.81..1.12) |
| Dispatch        | 190.68 ms ± 13.78 (176.11..217.45)     | 0.97x ± 0.09 (0.87..1.03) |
| Fannkuch        | 132.53 ms ± 18.65 (113.06..166.66)     | 1.05x ± 0.15 (1.00..1.15) |
| Fibonacci       | 388.18 ms ± 21.44 (366.46..426.65)     | 1.05x ± 0.07 (0.97..1.08) |
| FieldLoop       | 346.85 ms ± 23.86 (304.41..378.93)     | 0.98x ± 0.09 (0.84..1.05) |
| GraphSearch     | 81.46 ms ± 3.98 (77.34..88.81)         | 0.98x ± 0.07 (0.90..1.04) |
| IntegerLoop     | 344.56 ms ± 35.82 (304.82..436.43)     | 1.05x ± 0.12 (0.98..1.12) |
| JsonSmall       | 211.13 ms ± 29.43 (189.15..282.89)     | 0.97x ± 0.16 (0.83..1.08) |
| List            | 245.51 ms ± 13.28 (228.22..265.10)     | 1.02x ± 0.09 (0.89..1.12) |
| Loop            | 417.66 ms ± 17.49 (389.47..442.49)     | 0.92x ± 0.08 (0.80..1.05) |
| Mandelbrot      | 272.77 ms ± 18.55 (247.10..304.97)     | 0.97x ± 0.17 (0.67..1.07) |
| NBody           | 229.51 ms ± 21.41 (188.84..268.65)     | 0.91x ± 0.13 (0.77..1.07) |
| PageRank        | 308.44 ms ± 24.98 (278.38..354.15)     | 1.01x ± 0.11 (0.86..1.09) |
| Permute         | 326.18 ms ± 26.02 (281.97..364.30)     | 0.96x ± 0.14 (0.78..1.12) |
| Queens          | 260.12 ms ± 29.42 (225.41..324.86)     | 1.09x ± 0.13 (1.03..1.17) |
| QuickSort       | 74.60 ms ± 5.46 (69.01..86.30)         | 0.93x ± 0.12 (0.78..1.08) |
| Recurse         | 285.19 ms ± 13.45 (262.92..311.85)     | 1.01x ± 0.08 (0.92..1.11) |
| Richards        | 4389.05 ms ± 180.56 (4054.82..4598.70) | 1.04x ± 0.06 (0.98..1.09) |
| Sieve           | 462.54 ms ± 27.60 (423.33..504.71)     | 1.10x ± 0.08 (1.05..1.17) |
| Storage         | 94.77 ms ± 10.98 (85.43..113.54)       | 1.06x ± 0.15 (0.90..1.17) |
| Sum             | 185.48 ms ± 18.92 (157.21..215.67)     | 1.08x ± 0.17 (0.86..1.25) |
| Towers          | 327.16 ms ± 33.24 (297.54..408.98)     | 1.01x ± 0.12 (0.93..1.08) |
| TreeSort        | 168.61 ms ± 19.48 (148.06..219.50)     | 1.03x ± 0.14 (0.89..1.15) |
| WhileLoop       | 406.59 ms ± 34.09 (370.11..458.88)     | 1.09x ± 0.11 (0.97..1.17) |
|                 |                                        |                           |
| Average Speedup |               (baseline)               | 1.01x ± 0.02 (0.89..1.10) |
+-----------------+----------------------------------------+---------------------------+

The raw ReBench data files are available for download here: baseline and head

Bytecode interpreter

+-----------------+---------------------------------------+---------------------------+
| Benchmark       | master (base)                         | feat/inline-fields (head) |
+-----------------+---------------------------------------+---------------------------+
| Bounce          | 77.34 ms ± 3.57 (71.93..83.15)        | 0.63x ± 0.09 (0.48..0.77) |
| BubbleSort      | 103.36 ms ± 3.07 (98.04..108.06)      | 0.60x ± 0.05 (0.54..0.66) |
| DeltaBlue       | 66.80 ms ± 8.67 (57.24..87.60)        | 0.65x ± 0.11 (0.55..0.72) |
| Dispatch        | 77.99 ms ± 2.64 (75.08..81.27)        | 0.59x ± 0.08 (0.46..0.69) |
| Fannkuch        | 49.18 ms ± 3.45 (45.28..57.06)        | 0.65x ± 0.08 (0.53..0.76) |
| Fibonacci       | 143.38 ms ± 7.77 (134.52..155.29)     | 0.74x ± 0.06 (0.66..0.79) |
| FieldLoop       | 166.73 ms ± 13.36 (151.33..191.09)    | 1.02x ± 0.09 (0.98..1.11) |
| GraphSearch     | 34.48 ms ± 4.82 (30.50..45.95)        | 0.57x ± 0.14 (0.40..0.75) |
| IntegerLoop     | 146.47 ms ± 13.85 (133.43..179.00)    | 0.65x ± 0.08 (0.55..0.73) |
| JsonSmall       | 101.89 ms ± 18.32 (80.95..133.50)     | 0.81x ± 0.22 (0.61..1.03) |
| List            | 110.44 ms ± 8.94 (96.51..124.43)      | 0.64x ± 0.07 (0.57..0.70) |
| Loop            | 190.00 ms ± 7.89 (182.64..208.73)     | 0.69x ± 0.06 (0.62..0.76) |
| Mandelbrot      | 116.59 ms ± 11.24 (104.09..138.99)    | 0.85x ± 0.11 (0.75..0.94) |
| NBody           | 84.22 ms ± 6.07 (79.27..99.11)        | 0.67x ± 0.08 (0.58..0.77) |
| PageRank        | 135.32 ms ± 20.33 (113.04..172.63)    | 0.70x ± 0.13 (0.61..0.84) |
| Permute         | 114.25 ms ± 8.34 (106.52..134.45)     | 0.71x ± 0.06 (0.67..0.79) |
| Queens          | 104.35 ms ± 17.33 (88.45..135.14)     | 0.73x ± 0.15 (0.65..0.88) |
| QuickSort       | 28.93 ms ± 0.83 (27.74..30.82)        | 0.71x ± 0.06 (0.64..0.80) |
| Recurse         | 122.14 ms ± 19.56 (109.85..172.76)    | 0.82x ± 0.14 (0.72..0.87) |
| Richards        | 1486.01 ms ± 80.72 (1385.83..1628.36) | 0.57x ± 0.04 (0.54..0.62) |
| Sieve           | 176.72 ms ± 13.92 (160.91..204.20)    | 0.69x ± 0.08 (0.59..0.80) |
| Storage         | 33.96 ms ± 1.56 (31.90..36.95)        | 0.71x ± 0.09 (0.58..0.90) |
| Sum             | 72.34 ms ± 7.30 (65.42..87.66)        | 0.65x ± 0.10 (0.53..0.82) |
| Towers          | 134.51 ms ± 21.65 (113.67..188.97)    | 0.68x ± 0.13 (0.58..0.77) |
| TreeSort        | 55.40 ms ± 8.94 (46.92..72.11)        | 0.69x ± 0.13 (0.61..0.76) |
| WhileLoop       | 193.77 ms ± 23.45 (169.07..231.40)    | 1.07x ± 0.17 (0.86..1.17) |
|                 |                                       |                           |
| Average Speedup |              (baseline)               | 0.71x ± 0.02 (0.57..1.07) |
+-----------------+---------------------------------------+---------------------------+

The raw ReBench data files are available for download here: baseline and head

The benchmarks were run using ReBench v1.2.0
The statistical analysis was done using rebench-tabler v0.1.0

The source code of this benchmark runner is available as a GitHub Gist for more details about the setup

[OctaveLarose]

Current results on our machines: https://rebench.stefan-marr.de/som-rs/compare/aa52b413ea453d496882546092419c839d56633f..a596c147c4b629fa1feaa89be2767744fb34e134

Assuming I didn't mess up the comparison (I don't think I did), it's a big slowdown - though not on FieldLoop for some reason?