feat: Upstream NIOAsyncRuntime from PassiveLogic to swift-nio. NIOAsyncRuntime is a new module that provides MTELG and NIOThreadPool using Swift Concurrency. It compiles to wasm and runs in the browser.

Author: scottmarchant

Benchmarks/Benchmarks/NIOAsyncRuntimeBenchmarks/Benchmarks.swift

@@ -0,0 +1,122 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2026 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+// NOTE: By and large the benchmarks here were ported from swift-nio
+// to allow side-by-side performance comparison
+//
+// See https://github.com/apple/swift-nio/blob/main/Benchmarks/Benchmarks/NIOPosixBenchmarks/Benchmarks.swift
+
+import Benchmark
+import NIOAsyncRuntime
+import NIOCore
+
+private let eventLoop = MultiThreadedEventLoopGroup.singleton.next()
+
+let benchmarks = {
+    let defaultMetrics: [BenchmarkMetric] = [
+        .mallocCountTotal,
+        .contextSwitches,
+        .wallClock,
+    ]
+
+    Benchmark(
+        "MTELG.immediateTasksThroughput",
+        configuration: Benchmark.Configuration(
+            metrics: defaultMetrics,
+            scalingFactor: .mega,
+            maxDuration: .seconds(10_000_000),
+            maxIterations: 5
+        )
+    ) { benchmark in
+        func noOp() {}
+        for _ in benchmark.scaledIterations {
+            eventLoop.execute { noOp() }
+        }
+    }
+
+    Benchmark(
+        "MTELG.scheduleTask(in:_:)",
+        configuration: Benchmark.Configuration(
+            metrics: defaultMetrics,
+            scalingFactor: .mega,
+            maxDuration: .seconds(10_000_000),
+            maxIterations: 5
+        )
+    ) { benchmark in
+        for _ in benchmark.scaledIterations {
+            eventLoop.scheduleTask(in: .hours(1), {})
+        }
+    }
+
+    Benchmark(
+        "MTELG.scheduleCallback(in:_:)",
+        configuration: Benchmark.Configuration(
+            metrics: defaultMetrics,
+            scalingFactor: .mega,
+            maxDuration: .seconds(10_000_000),
+            maxIterations: 5
+        )
+    ) { benchmark in
+        final class Timer: NIOScheduledCallbackHandler {
+            func handleScheduledCallback(eventLoop: some EventLoop) {}
+        }
+        let timer = Timer()
+
+        benchmark.startMeasurement()
+        for _ in benchmark.scaledIterations {
+            let handle = try! eventLoop.scheduleCallback(in: .hours(1), handler: timer)
+        }
+    }
+
+    Benchmark(
+        "Jump to EL and back using execute and unsafecontinuation",
+        configuration: .init(
+            metrics: defaultMetrics,
+            scalingFactor: .kilo
+        )
+    ) { benchmark in
+        for _ in benchmark.scaledIterations {
+            await withUnsafeContinuation { (continuation: UnsafeContinuation<Void, Never>) in
+                eventLoop.execute {
+                    continuation.resume()
+                }
+            }
+        }
+    }
+
+    final actor Foo {
+        nonisolated public let unownedExecutor: UnownedSerialExecutor
+
+        init(eventLoop: any EventLoop) {
+            self.unownedExecutor = eventLoop.executor.asUnownedSerialExecutor()
+        }
+
+        func foo() {
+            blackHole(Void())
+        }
+    }
+
+    Benchmark(
+        "Jump to EL and back using actor with EL executor",
+        configuration: .init(
+            metrics: defaultMetrics,
+            scalingFactor: .kilo
+        )
+    ) { benchmark in
+        let actor = Foo(eventLoop: eventLoop)
+        for _ in benchmark.scaledIterations {
+            await actor.foo()
+        }
+    }
+}

Benchmarks/Benchmarks/NIOAsyncRuntimeBenchmarks/Util/GlobalExecutor.swift

@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2026 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+// NOTE: By and large the benchmarks here were ported from swift-nio
+// to allow side-by-side performance comparison
+//
+// See https://github.com/apple/swift-nio/blob/main/Benchmarks/Benchmarks/NIOPosixBenchmarks/Benchmarks.swift
+
+#if canImport(Darwin)
+import Darwin.C
+#elseif canImport(Glibc)
+import Glibc
+#else
+#error("Unsupported platform.")
+#endif
+
+// This file allows us to hook the global executor which
+// we can use to mimic task executors for now.
+typealias EnqueueGlobalHook =
+    @convention(thin) (UnownedJob, @convention(thin) (UnownedJob) -> Void) -> Void
+
+var swiftTaskEnqueueGlobalHook: EnqueueGlobalHook? {
+    get { _swiftTaskEnqueueGlobalHook.pointee }
+    set { _swiftTaskEnqueueGlobalHook.pointee = newValue }
+}
+
+private let _swiftTaskEnqueueGlobalHook: UnsafeMutablePointer<EnqueueGlobalHook?> =
+    dlsym(dlopen(nil, RTLD_LAZY), "swift_task_enqueueGlobal_hook").assumingMemoryBound(
+        to: EnqueueGlobalHook?.self
+    )

Package.swift

@@ -47,6 +47,7 @@ let package = Package(
         .library(name: "NIO", targets: ["NIO"]),
         .library(name: "NIOEmbedded", targets: ["NIOEmbedded"]),
         .library(name: "NIOPosix", targets: ["NIOPosix"]),
+        .library(name: "NIOAsyncRuntime", targets: ["NIOAsyncRuntime"]),
         .library(name: "_NIOConcurrency", targets: ["_NIOConcurrency"]),
         .library(name: "NIOTLS", targets: ["NIOTLS"]),
         .library(name: "NIOHTTP1", targets: ["NIOHTTP1"]),
@@ -112,6 +113,15 @@ let package = Package(
             resources: includePrivacyManifest ? [.copy("PrivacyInfo.xcprivacy")] : [],
             swiftSettings: swiftSettings
         ),
+        .target(
+            name: "NIOAsyncRuntime",
+            dependencies: [
+                "NIOCore",
+                swiftAtomics,
+            ],
+            exclude: ["README.md"],
+            swiftSettings: swiftSettings
+        ),
         .target(
             name: "NIO",
             dependencies: [