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Сидоренко Егор АлекчеевичandCodex
ca27b2de97
Resolve the allocator and lockfile conflicts against 8f376a471. Keep
main's horizon_threads allocator, startup configuration, and dependency
settings unchanged. Retain windows-mimalloc as a compatibility no-op and
keep the independent, opt-in Segment Heap resource experiment.
Co-Authored-By: Codex (GPT-6) <[email protected]>
70 lines
3.7 KiB
Markdown
70 lines
3.7 KiB
Markdown
# Windows allocator experiments
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The normal client already uses mimalloc through `horizon_threads::Allocator`,
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including its startup configuration and memory-release behavior. It does not
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request Windows Segment Heap. An off-by-default Cargo feature allows a separate
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experiment with the Win32 heap used by native libraries:
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| Feature | Effect on Windows |
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| --- | --- |
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| `windows-segment-heap` | Embeds a manifest requesting Segment Heap for Win32 heap APIs in this package's executables. |
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| `windows-mimalloc` | Compatibility no-op for earlier experiment commands; the client already uses mimalloc without this feature. |
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Neither feature changes non-Windows builds relative to the current main branch.
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Segment Heap is a build option, not a mod or runtime setting; changing it requires
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rebuilding and restarting the client. It does not replace or reconfigure the Rust
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allocator. Native libraries can still use Windows heap APIs even though Rust uses
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mimalloc. No frame-rate improvement is guaranteed.
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```sh
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# Current mimalloc baseline, then add Segment Heap. Keep the same profile.
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cargo build --profile fast -p horizon-client --bin horizon-client
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cargo build --profile fast -p horizon-client --bin horizon-client --features windows-segment-heap
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# Older commands still build, but these repeat the two variants above.
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cargo build --profile fast -p horizon-client --bin horizon-client --features windows-mimalloc
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cargo build --profile fast -p horizon-client --bin horizon-client --features windows-segment-heap,windows-mimalloc
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```
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Copy each executable to a separate experiment directory before building the next
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variant, or use a separate `CARGO_TARGET_DIR`. Keep prepared resources and worlds
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outside version control. Use disposable copies of a world and isolated data
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directories for tests, following [AGENTS.md](../AGENTS.md).
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Segment Heap is supported starting with Windows 10 version 2004 (build 19041),
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according to Microsoft's [application manifest documentation](https://learn.microsoft.com/en-us/windows/win32/sbscs/application-manifests#heaptype).
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The manifest leaves the optional architecture unspecified and keeps the usual `asInvoker`
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execution level. The existing icon and version resources are compiled together
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with it through the existing Windows-host resource build step. Cross-compiling
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that manifest from a non-Windows host is not supported by this build step.
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Builds on earlier Windows versions have not been tested.
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## Validate the executable
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On Windows, extract the manifest from a built executable using the Windows SDK's
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`mt.exe` (PowerShell syntax):
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```powershell
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mt.exe '-inputresource:target/fast/horizon-client.exe;#1' '-out:client.manifest'
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mt.exe -manifest client.manifest -validate_manifest
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```
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Check that the feature build contains `SegmentHeap` in the
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`http://schemas.microsoft.com/SMI/2020/WindowsSettings` namespace. The baseline
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must not contain this element. Confirm Explorer still shows Horizon's icon for
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both builds. Inspecting the final executable matters: a valid source XML file
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alone does not prove that the linker embedded it.
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## Measure separately
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Use the same commit, compiler, profile, settings, driver configuration, world
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copy, warm-up period and flight route for both variants. Alternate their
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order across repeated sessions. Capture individual frame times, their p99 and
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maximum, memory use and average FPS. Record game FPS limits, the display refresh
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rate and driver-level VSync: a driver override can cap FPS even when game VSync
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is disabled.
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Compare the current mimalloc baseline with that same build plus Segment Heap.
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The compatibility feature cannot measure system allocation versus mimalloc.
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Results from older system-allocator builds, or builds that also change meshing
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or LOD retirement, cannot establish the benefit of Segment Heap on current main.
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