[wasm] Reduce number of calls to setTimer

src/libraries/System.Private.Runtime.InteropServices.JavaScript/tests/System.Private.Runtime.InteropServices.JavaScript.Tests.csproj

@@ -17,6 +17,11 @@
     <Compile Include="System\Runtime\InteropServices\JavaScript\HelperMarshal.cs" />
     <Compile Include="System\Runtime\InteropServices\JavaScript\Http\HttpRequestMessageTest.cs" />
     <Compile Include="System\Runtime\InteropServices\JavaScript\ParallelTests.cs" />
+    <Compile Include="System\Runtime\InteropServices\JavaScript\TimerTests.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <WasmExtraFilesToDeploy Include="timers.js" />
   </ItemGroup>
   <ItemGroup>
     <!-- Part of the shared framework but not exposed. -->

src/libraries/System.Private.Runtime.InteropServices.JavaScript/tests/System/Runtime/InteropServices/JavaScript/TimerTests.cs

@@ -0,0 +1,116 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace System.Runtime.InteropServices.JavaScript.Tests
+{
+    // V8's implementation of setTimer ignores delay parameter and always run immediately. So it could not be used to test this.
+    [ConditionalClass(typeof(PlatformDetection), nameof(PlatformDetection.IsBrowserDomSupported))]
+    public class TimerTests : IAsyncLifetime
+    {
+        static JSObject _timersHelper;
+        static Function _installWrapper;
+        static Function _getRegisterCount;
+        static Function _getHitCount;
+        static Function _cleanupWrapper;
+        // static Function _log;
+
+        public static IEnumerable<object[]> TestCases()
+        {
+            yield return new object[] { new int[0], 0, null, null };
+            yield return new object[] { new[] { 10 }, 1 , null, null };
+            yield return new object[] { new[] { 10, 5 }, 2 , null, null };
+            yield return new object[] { new[] { 10, 20 }, 1 , null, null };
+            yield return new object[] { new[] { 800, 600, 400, 200, 050 }, 5, 13, 9 };
+        }
+
+        [Theory]
+        [MemberData(nameof(TestCases))]
+        public async Task TestTimers(int[] timeouts, int? expectedSetCounter, int? expectedSetCounterAfterCleanUp, int? expectedHitCount)
+        {
+            int wasCalled = 0;
+            Timer[] timers = new Timer[timeouts.Length];
+            try
+            {
+                // _log.Call(null, $"Waiting for runtime to settle");
+                await Task.Delay(2000);
+                _installWrapper.Call();
+                // _log.Call(null, $"Ready!");
+
+                for (int i = 0; i < timeouts.Length; i++)
+                {
+                    int index = i;
+                    // _log.Call(null, $"Registering {index} delay {timeouts[i]}");
+                    timers[i] = new Timer((_) =>
+                    {
+                        // _log.Call(null, $"In timer{index}");
+                        wasCalled++;
+                    }, null, timeouts[i], 0);
+                }
+
+                var setCounter = (int)_getRegisterCount.Call();
+                Assert.True(0 == wasCalled, $"wasCalled: {wasCalled}");
+                Assert.True((expectedSetCounter ?? timeouts.Length) == setCounter, $"setCounter: actual {setCounter} expected {expectedSetCounter}");
+
+            }
+            finally
+            {
+                await WaitForCleanup();
+                Assert.True(timeouts.Length == wasCalled, $"wasCalled: actual {wasCalled} expected {timeouts.Length}");
+
+                if (expectedSetCounterAfterCleanUp != null)
+                {
+                    var setCounter = (int)_getRegisterCount.Call();
+                    Assert.True(expectedSetCounterAfterCleanUp.Value == setCounter, $"setCounter: actual {setCounter} expected {expectedSetCounterAfterCleanUp.Value}");
+                }
+
+                if (expectedHitCount != null)
+                {
+                    var hitCounter = (int)_getHitCount.Call();
+                    Assert.True(expectedHitCount == hitCounter, $"hitCounter: actual {hitCounter} expected {expectedHitCount}");
+                }
+
+                for (int i = 0; i < timeouts.Length; i++)
+                {
+                    timers[i].Dispose();
+                }
+            }
+        }
+
+        private async Task WaitForCleanup()
+        {
+            // _log.Call(null, "wait for cleanup begin");
+            await Task.Delay(1200);
+            _cleanupWrapper.Call();
+            // _log.Call(null, "wait for cleanup end");
+        }
+
+        public async Task InitializeAsync()
+        {
+            if (_timersHelper == null)
+            {
+                Function helper = new Function(@"
+                    const loadTimersJs = async () => {
+                        await import('./timers.js');
+                    };
+                    return loadTimersJs();
+                ");
+                await (Task)helper.Call();
+
+                _timersHelper = (JSObject)Runtime.GetGlobalObject("timersHelper");
+                _installWrapper = (Function)_timersHelper.GetObjectProperty("install");
+                _getRegisterCount = (Function)_timersHelper.GetObjectProperty("getRegisterCount");
+                _getHitCount = (Function)_timersHelper.GetObjectProperty("getHitCount");
+                _cleanupWrapper = (Function)_timersHelper.GetObjectProperty("cleanup");
+                // var console = (JSObject)Runtime.GetGlobalObject("console");
+                // _log = (Function)console.GetObjectProperty("log");
+            }
+        }
+
+        public Task DisposeAsync() => Task.CompletedTask;
+    }
+}

src/libraries/System.Private.Runtime.InteropServices.JavaScript/tests/timers.js

@@ -0,0 +1,44 @@
+class TimersHelper {
+    install() {
+        const measuredCallbackName = "mono_wasm_set_timeout_exec";
+        globalThis.registerCount = 0;
+        globalThis.hitCount = 0;
+        // console.log("install")
+        if (!globalThis.originalSetTimeout) {
+            globalThis.originalSetTimeout = globalThis.setTimeout;
+        }
+        globalThis.setTimeout = (cb, time) => {
+            var start = Date.now().valueOf();
+            if (cb.name === measuredCallbackName) {
+                globalThis.registerCount++;
+                // console.log(`registerCount: ${globalThis.registerCount} now:${start} delay:${time}`)
+            }
+            return globalThis.originalSetTimeout(() => {
+                if (cb.name === measuredCallbackName) {
+                    var hit = Date.now().valueOf();
+                    globalThis.hitCount++;
+                    var delta = hit - start;
+                    // console.log(`hitCount: ${globalThis.hitCount} now:${hit} delay:${time} delta:${delta}`)
+                }
+                cb();
+            }, time);
+        };
+    }
+
+    getRegisterCount() {
+        // console.log(`registerCount: ${globalThis.registerCount} `)
+        return globalThis.registerCount;
+    }
+
+    getHitCount() {
+        // console.log(`hitCount: ${globalThis.hitCount} `)
+        return globalThis.hitCount;
+    }
+
+    cleanup() {
+        // console.log(`cleanup registerCount: ${globalThis.registerCount} hitCount: ${globalThis.hitCount} `)
+        globalThis.setTimeout = globalThis.originalSetTimeout;
+    }
+}
+
+globalThis.timersHelper = new TimersHelper();

src/mono/System.Private.CoreLib/src/System/Threading/TimerQueue.Browser.Mono.cs

@@ -17,7 +17,9 @@ internal partial class TimerQueue
     {
         private static List<TimerQueue>? s_scheduledTimers;
         private static List<TimerQueue>? s_scheduledTimersToFire;
+        private static long s_shortestDueTimeMs = long.MaxValue;
 
+        // this means that it's in the s_scheduledTimers collection, not that it's the one which would run on the next TimeoutCallback
         private bool _isScheduled;
         private long _scheduledDueTimeMs;
 
@@ -27,49 +29,91 @@ private TimerQueue(int id)
 
         [DynamicDependency("TimeoutCallback")]
         // The id argument is unused in netcore
+        // This replaces the current pending setTimeout with shorter one
         [MethodImplAttribute(MethodImplOptions.InternalCall)]
         private static extern void SetTimeout(int timeout, int id);
 
         // Called by mini-wasm.c:mono_set_timeout_exec
         private static void TimeoutCallback()
         {
-            int shortestWaitDurationMs = PumpTimerQueue();
+            // always only have one scheduled at a time
+            s_shortestDueTimeMs = long.MaxValue;
 
-            if (shortestWaitDurationMs != int.MaxValue)
-            {
-                SetTimeout((int)shortestWaitDurationMs, 0);
-            }
+            long currentTimeMs = TickCount64;
+            ReplaceNextSetTimeout(PumpTimerQueue(currentTimeMs), currentTimeMs);
         }
 
+        // this is called with shortest of timers scheduled on the particular TimerQueue
         private bool SetTimer(uint actualDuration)
         {
             Debug.Assert((int)actualDuration >= 0);
-            long dueTimeMs = TickCount64 + (int)actualDuration;
+            long currentTimeMs = TickCount64;
             if (!_isScheduled)
             {
                 s_scheduledTimers ??= new List<TimerQueue>(Instances.Length);
                 s_scheduledTimersToFire ??= new List<TimerQueue>(Instances.Length);
                 s_scheduledTimers.Add(this);
                 _isScheduled = true;
             }
-            _scheduledDueTimeMs = dueTimeMs;
-            SetTimeout((int)actualDuration, 0);
+
+            _scheduledDueTimeMs = currentTimeMs + (int)actualDuration;
+
+            ReplaceNextSetTimeout(ShortestDueTime(), currentTimeMs);
 
             return true;
         }
 
-        private static int PumpTimerQueue()
+        // shortest time of all TimerQueues
+        private static void ReplaceNextSetTimeout(long shortestDueTimeMs, long currentTimeMs)
         {
-            if (s_scheduledTimersToFire == null)
+            if (shortestDueTimeMs == int.MaxValue)
+            {
+                return;
+            }
+
+            // this also covers s_shortestDueTimeMs = long.MaxValue when none is scheduled
+            if (s_shortestDueTimeMs > shortestDueTimeMs)
+            {
+                s_shortestDueTimeMs = shortestDueTimeMs;
+                int shortestWait = Math.Max((int)(shortestDueTimeMs - currentTimeMs), 0);
+                // this would cancel the previous schedule and create shorter one
+                // it is expensive call
+                SetTimeout(shortestWait, 0);
+            }
+        }
+
+        private static long ShortestDueTime()
+        {
+            if (s_scheduledTimers == null)
             {
                 return int.MaxValue;
             }
 
+            long shortestDueTimeMs = long.MaxValue;
+            var timers = s_scheduledTimers!;
+            for (int i = timers.Count - 1; i >= 0; --i)
+            {
+                TimerQueue timer = timers[i];
+                if (timer._scheduledDueTimeMs < shortestDueTimeMs)
+                {
+                    shortestDueTimeMs = timer._scheduledDueTimeMs;
+                }
+            }
+
+            return shortestDueTimeMs;
+        }
+
+        private static long PumpTimerQueue(long currentTimeMs)
+        {
+            if (s_scheduledTimersToFire == null)
+            {
+                return ShortestDueTime();
+            }
+
             List<TimerQueue> timersToFire = s_scheduledTimersToFire!;
             List<TimerQueue> timers;
             timers = s_scheduledTimers!;
-            long currentTimeMs = TickCount64;
-            int shortestWaitDurationMs = int.MaxValue;
+            long shortestDueTimeMs = int.MaxValue;
             for (int i = timers.Count - 1; i >= 0; --i)
             {
                 TimerQueue timer = timers[i];
@@ -88,9 +132,9 @@ private static int PumpTimerQueue()
                     continue;
                 }
 
-                if (waitDurationMs < shortestWaitDurationMs)
+                if (timer._scheduledDueTimeMs < shortestDueTimeMs)
                 {
-                    shortestWaitDurationMs = (int)waitDurationMs;
+                    shortestDueTimeMs = timer._scheduledDueTimeMs;
                 }
             }
 
@@ -103,7 +147,7 @@ private static int PumpTimerQueue()
                 timersToFire.Clear();
             }
 
-            return shortestWaitDurationMs;
+            return shortestDueTimeMs;
         }
     }
 }

src/mono/wasm/runtime/rollup.config.js

@@ -35,7 +35,8 @@ const terserConfig = {
     },
     mangle: {
         // because of stack walk at src/mono/wasm/debugger/BrowserDebugProxy/MonoProxy.cs
-        keep_fnames: /(mono_wasm_runtime_ready|mono_wasm_fire_debugger_agent_message)/,
+        // and unit test at src\libraries\System.Private.Runtime.InteropServices.JavaScript\tests\timers.js
+        keep_fnames: /(mono_wasm_runtime_ready|mono_wasm_fire_debugger_agent_message|mono_wasm_set_timeout_exec)/,
     },
 };
 const plugins = isDebug ? [writeOnChangePlugin()] : [terser(terserConfig), writeOnChangePlugin()];

src/mono/wasm/runtime/scheduling.ts

@@ -3,7 +3,6 @@
 
 import cwraps from "./cwraps";
 
-const timeout_queue: Function[] = [];
 let spread_timers_maximum = 0;
 export let isChromium = false;
 let pump_count = 0;
@@ -19,23 +18,14 @@ if (globalThis.navigator) {
 }
 
 function pump_message() {
-    while (timeout_queue.length > 0) {
-        --pump_count;
-        const cb: Function = timeout_queue.shift()!;
-        cb();
-    }
     while (pump_count > 0) {
         --pump_count;
         cwraps.mono_background_exec();
     }
 }
 
-function mono_wasm_set_timeout_exec(id: number) {
-    cwraps.mono_set_timeout_exec(id);
-}
-
 export function prevent_timer_throttling(): void {
-    if (isChromium) {
+    if (!isChromium) {
         return;
     }
 
@@ -48,7 +38,7 @@ export function prevent_timer_throttling(): void {
     for (let schedule = next_reach_time; schedule < desired_reach_time; schedule += light_throttling_frequency) {
         const delay = schedule - now;
         setTimeout(() => {
-            mono_wasm_set_timeout_exec(0);
+            cwraps.mono_set_timeout_exec(0);
             pump_count++;
             pump_message();
         }, delay);
@@ -58,21 +48,17 @@ export function prevent_timer_throttling(): void {
 
 export function schedule_background_exec(): void {
     ++pump_count;
-    if (typeof globalThis.setTimeout === "function") {
-        globalThis.setTimeout(pump_message, 0);
-    }
+    setTimeout(pump_message, 0);
 }
 
+let lastScheduledTimeoutId: any = undefined;
 export function mono_set_timeout(timeout: number, id: number): void {
-
-    if (typeof globalThis.setTimeout === "function") {
-        globalThis.setTimeout(function () {
-            mono_wasm_set_timeout_exec(id);
-        }, timeout);
-    } else {
-        ++pump_count;
-        timeout_queue.push(function () {
-            mono_wasm_set_timeout_exec(id);
-        });
+    function mono_wasm_set_timeout_exec() {
+        cwraps.mono_set_timeout_exec(id);
     }
-}
+    if (lastScheduledTimeoutId) {
+        clearTimeout(lastScheduledTimeoutId);
+        lastScheduledTimeoutId = undefined;
+    }
+    lastScheduledTimeoutId = setTimeout(mono_wasm_set_timeout_exec, timeout);
+}