EXPERIMENT: MemDecoder tweak
#109910
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EXPERIMENT: MemDecoder tweak
#109910
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@bors try @rust-timer queue |
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⌛ Trying commit 23a77dc with merge 7d210e27e7028d72af6c2cbc026edc71c2d65abc... |
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☀️ Try build successful - checks-actions |
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Finished benchmarking commit (7d210e27e7028d72af6c2cbc026edc71c2d65abc): comparison URL. Overall result: ✅ improvements - no action neededBenchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf. @bors rollup=never Instruction countThis is a highly reliable metric that was used to determine the overall result at the top of this comment.
Max RSS (memory usage)ResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
CyclesThis benchmark run did not return any relevant results for this metric. |
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Apr 26, 2023
Rewrite MemDecoder around pointers not a slice This is basically rust-lang#109910 but I'm being a lot more aggressive. The pointer-based structure means that it makes a lot more sense to absorb more complexity into `MemDecoder`, most of the diff is just complexity moving from one place to another. The primary argument for this structure is that we only incur a single bounds check when doing multi-byte reads from a `MemDecoder`. With the slice-based implementation we need to do those with `data[position..position + len]` , which needs to account for `position + len` wrapping. It would be possible to dodge the first bounds check if we stored a slice that starts at `position`, but that would require updating the pointer and length on every read. This PR also embeds the failure path in a separate function, which means that this PR should subsume all the perf wins observed in rust-lang#109867.
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Apr 26, 2023
Rewrite MemDecoder around pointers not a slice This is basically rust-lang/rust#109910 but I'm being a lot more aggressive. The pointer-based structure means that it makes a lot more sense to absorb more complexity into `MemDecoder`, most of the diff is just complexity moving from one place to another. The primary argument for this structure is that we only incur a single bounds check when doing multi-byte reads from a `MemDecoder`. With the slice-based implementation we need to do those with `data[position..position + len]` , which needs to account for `position + len` wrapping. It would be possible to dodge the first bounds check if we stored a slice that starts at `position`, but that would require updating the pointer and length on every read. This PR also embeds the failure path in a separate function, which means that this PR should subsume all the perf wins observed in rust-lang/rust#109867.
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Apr 20, 2024
Rewrite MemDecoder around pointers not a slice This is basically rust-lang/rust#109910 but I'm being a lot more aggressive. The pointer-based structure means that it makes a lot more sense to absorb more complexity into `MemDecoder`, most of the diff is just complexity moving from one place to another. The primary argument for this structure is that we only incur a single bounds check when doing multi-byte reads from a `MemDecoder`. With the slice-based implementation we need to do those with `data[position..position + len]` , which needs to account for `position + len` wrapping. It would be possible to dodge the first bounds check if we stored a slice that starts at `position`, but that would require updating the pointer and length on every read. This PR also embeds the failure path in a separate function, which means that this PR should subsume all the perf wins observed in rust-lang/rust#109867.
RalfJung
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Apr 27, 2024
Rewrite MemDecoder around pointers not a slice This is basically rust-lang/rust#109910 but I'm being a lot more aggressive. The pointer-based structure means that it makes a lot more sense to absorb more complexity into `MemDecoder`, most of the diff is just complexity moving from one place to another. The primary argument for this structure is that we only incur a single bounds check when doing multi-byte reads from a `MemDecoder`. With the slice-based implementation we need to do those with `data[position..position + len]` , which needs to account for `position + len` wrapping. It would be possible to dodge the first bounds check if we stored a slice that starts at `position`, but that would require updating the pointer and length on every read. This PR also embeds the failure path in a separate function, which means that this PR should subsume all the perf wins observed in rust-lang/rust#109867.
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@saethlin nerd-sniped me in #109867 🙂
I played a bit, and it looks like using an iterator could avoid some bounds checking (https://rust.godbolt.org/z/av4b168T5) by not needing to check the
positionseparately.Let's see what perf has to say 🤞
r? @ghost