Wasmtime GitHub notifications bot (Sep 23 2022 at 21:38): Wasmtime GitHub notifications bot (Sep 23 2022 at 21:38):jameysharp requested cfallin for a review on PR #4951.
Wasmtime GitHub notifications bot (Sep 23 2022 at 21:38):jameysharp opened PR #4951 from shrink-abiarg to main:
We weren't using the "union" cargo feature for the smallvec crate, which reduces the size of a SmallVec by one machine word. This feature requires Rust 1.49 but we already require much newer versions.
I also reduced ABIArgSlot::Stack::offset from i64 to i32, so it fits in the same space as ABIArgSlot::Reg::reg. This eliminates all padding from ABIArgSlot, saving 8 bytes there. Without that change, ABIArg wouldn't shrink even though it contains a SmallVec.
When using Wasmtime to compile pulldown-cmark from Sightglass, this saves a decent amount of memory allocations and writes. According to
valgrind --tool=dhat:
- 6.3MiB (3.78%) less memory allocated over the program's lifetime
- 0.5MiB (4.16%) less memory allocated at maximum heap size
- 5.6MiB (1.94%) fewer bytes written to
- 0.5% fewer instructions executed
Reducing the size of SmallVecs also shrinks other types by varying amounts. Here are some types that shrink by quite a bit but aren't allocated often:
- 264 bytes: cranelift_codegen::machinst::buffer::MachBuffer
- 112 bytes: cranelift_codegen::machinst::abi::SigData
- 64 bytes: wasmtime_cranelift::compiler::CompilerContext
- 56 bytes: cranelift_codegen::context::Context
Here are some types which don't shrink by a lot, but are allocated very often:
- 16 bytes: cranelift_codegen::isa::x64::inst::CallInfo
- 16 bytes: cranelift_codegen::machinst::abi::Caller
- 8 bytes: cranelift_codegen::machinst::buffer::MachBranch
- 8 bytes: cranelift_frontend::ssa::SSABlockData
- 8 bytes: regalloc2::ion::data_structures::LiveBundle
- 8 bytes: regalloc2::ion::data_structures::LiveRange
- 8 bytes: regalloc2::ion::data_structures::SpillSet
- 8 bytes: regalloc2::ion::data_structures::SpillSlotList
- 8 bytes: regalloc2::ion::data_structures::VRegData
- 8 bytes: regalloc2::ion::process::AllocRegResult
- 8 bytes: regalloc2::moves::MoveVecWithScratch
- 8 bytes: regalloc2::moves::ParallelMoves
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Wasmtime GitHub notifications bot (Sep 23 2022 at 21:38):jameysharp requested fitzgen for a review on PR #4951.
Wasmtime GitHub notifications bot (Sep 23 2022 at 21:40):cfallin submitted PR review.
Wasmtime GitHub notifications bot (Sep 23 2022 at 22:49):jameysharp updated PR #4951 from shrink-abiarg to main.
Wasmtime GitHub notifications bot (Sep 23 2022 at 23:32):jameysharp merged PR #4951.
Last updated: Dec 23 2024 at 12:05 UTC