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⚡ Bolt: Optimize guest string comparison allocations and lock contention - #13

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manupawickramasinghe merged 1 commit into
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bolt/perf-kernel-strcmp-chunking-13762838680573309854
Jul 25, 2026
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⚡ Bolt: Optimize guest string comparison allocations and lock contention#13
manupawickramasinghe merged 1 commit into
mainfrom
bolt/perf-kernel-strcmp-chunking-13762838680573309854

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@manupawickramasinghe

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💡 What

Updated TryCompareStrings and TryCompareStringsCaseInsensitive to use chunked memory reading with 4KB stackalloc spans instead of 1-byte iterative reads. This prevents acquiring read locks per byte during string comparisons in guest space.

🎯 Subsystem & Bottleneck

  • Subsystem: Kernel HLE
  • Target File(s): src/SharpEmu.Libs/Kernel/KernelMemoryCompatExports.cs
  • Bottleneck Addressed: VirtualMemory locking contention and function call overhead caused by TryReadCompat being called per byte on long strings.

📜 Git & Contributor Context

  • Recent File History: Last modified < 7 days ago by @M.N Wickramasinghe.
  • Conflict Check: Explicit approval requested and obtained from user via chat prior to implementation. Verified change does not overlap with recent commits or reverted attempts.

📊 Measured Performance Impact

  • Allocation Delta: 0 B allocated per call (retained zero-allocation status while significantly improving performance).
  • Computational Impact: Drastically reduces lock contention by converting O(N) VirtualMemory lock acquisitions to O(N/4096).

🔬 Verification Checklist

  • Executed dotnet test (All tests passed)
  • Verified zero unexpected allocations in hot path
  • Verified formatting with dotnet format
  • Confirmed thread safety and emulation accuracy

PR created automatically by Jules for task 13762838680573309854 started by @manupawickramasinghe

- Updated `TryCompareStrings` and `TryCompareStringsCaseInsensitive` in `KernelMemoryCompatExports.cs`.
- Replaced per-byte `TryReadCompat` loops with 4KB chunked stack allocations.
- Ensures zero allocations while minimizing lock contention on `VirtualMemory` accesses during HLE syscall string operations.

Co-authored-by: manupawickramasinghe <73810867+manupawickramasinghe@users.noreply.github.com>
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Copilot AI review requested due to automatic review settings July 24, 2026 20:22

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2 participants