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KOBAYASHI Shuji
98d091436d
## Implementation Summary * Only keys and only values of hash table are contiguous to eliminate structure padding. * Change upper limit of `iv_tbl` size to `UINT16_MAX` (it seems to be acceptable in mruby because the total number of classes/modules immediately after starting Redmine is 20,000 or less). * `iv_tbl*` point hash buckets directly. ## Benchmark Summary Only the results of typical situations on 64-bit Word-boxing are present here. For more detailed information, including consideration, see below report (although most of the body is written in Japanese). * https://shuujii.github.io/mruby-iv-benchmark ### Memory Usage Lower value is better. | iv_tbl Size | Baseline | New | Factor | |------------:|---------------:|---------------:|-----------:| | 4 | 88B | 52B | 0.59091x | | 30 | 536B | 388B | 0.72388x | | 100 | 2072B | 1540B | 0.74324x | | 200 | 4120B | 3076B | 0.74660x | Although not mentioned in the above report, the memory usage of `mrbtest` (full-core gembox) is as follows in the result by Valgrind. * Baseline: 108,086 allocs, 16,313,122 bytes allocated * New: 94,273 allocs, 15,875,214 bytes allocated ### Performance Higher value is better. #### `mrb_obj_iv_set` | iv_tbl Size | Baseline | New | Factor | |------------:|---------------:|---------------:|-----------:| | 4 | 88.63003M i/s | 92.60611M i/s | 1.04486x | | 30 | 32.97066M i/s | 25.25095M i/s | 0.76586x | | 100 | 16.33224M i/s | 22.74998M i/s | 1.39295x | | 200 | 5.64484M i/s | 6.79949M i/s | 1.20455x | #### `mrb_obj_iv_get` | iv_tbl Size | Baseline | New | Factor | |------------:|---------------:|---------------:|-----------:| | 4 | 217.58391M i/s | 237.59912M i/s | 1.09199x | | 30 | 139.56195M i/s | 160.49470M i/s | 1.14999x | | 100 | 143.09716M i/s | 190.95047M i/s | 1.33441x | | 200 | 89.75291M i/s | 134.78717M i/s | 1.50176x | ### Binary Size Lower value is better. | File | Baseline | New | Factor | |:------------|---------------:|---------------:|-----------:| | mruby | 697,520B | 697,520B | 1.00000x | | libmruby.a | 1,046,570B | 1,046,682B | 0.99989x | ## Note The address in `struct RObject::iv` may change after initialization because `iv_tbl*` points directly to hash buckets. Therefore, the address cannot be copied and shared when include/prepend. So, when sharing `iv_tbl`, refer to it via the sharing source class. As a result, the following bug have also been fixed. * [An `iv_tbl` is not shared when a class includes or prepends an empty module](https://gist.github.com/shuujii/0ac23fa24b0c55b2c602b534d81e4a95)