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[Docs] Actors and locks: benchmark, lock census of the frame and rules - #66
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Research note docs/proposals/ActorsAndLocks.md with its two tools: - Examples/ConcurrencyBench: standalone package that measures a Swift actor against NSLock, NSRecursiveLock, OSAllocatedUnfairLock, Mutex and a serial queue (uncontended, contended, latency seen by a synchronous thread with the thread pool idle and saturated, a pass over 10,000 entities). - LockCensusTests: opt-in render test (UNTOLD_LOCK_CENSUS=1) that counts every NSLock / NSRecursiveLock acquisition in renderer.draw and attributes it to the engine function that made it. No engine code changes.
…velop Same text as the upstream PR (untoldengine#1294), so the note merges cleanly at the next sync. The counts are identical; the frame times are a second set of runs.
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What
Research on two questions, with the tools to re-run it. No engine code changes.
Contents
docs/proposals/ActorsAndLocks.md: results, proposed rules for engine and editor, review of the critical path, how to reproduce, limits.Examples/ConcurrencyBench: standalone package (macOS 15) that measures an actor againstNSLock,NSRecursiveLock,OSAllocatedUnfairLock,Mutexand a serial queue.Tests/UntoldEngineRenderTests/LockCensusTests.swift: opt-in test (UNTOLD_LOCK_CENSUS=1, skipped otherwise) that counts everyNSLock/NSRecursiveLockacquisition inrenderer.drawand names the function that made it.Findings (Mac16,5, release builds)
Task; the wait is 7 µs with the thread pool idle and 2.4 to 24 ms (median) with the pool full of asset jobs. A lock stays under 1 µs. Actors are fine at the async edges (the three the engine has) and in the editor.sceneglobal getter, the component-id map and the scene-channel render-mode check.renderer.drawby 6 to 7 %; removing per-access locking (ceiling, not a shippable change) cuts it by 25 to 28 %.Verified
swift build -c releaseofExamples/ConcurrencyBench, all five sections run.LockCensusTestsrun in debug and release at 1,000 and 4,000 cubes; skipped without the environment variable.swiftformat --linton the new Swift files, commit prefix check.