[browser][MT] pre-load threads early in dotnet.js

src/mono/browser/build/BrowserWasmApp.targets

@@ -121,7 +121,8 @@
 
     <PropertyGroup>
       <!-- TODO: set this from some user-facing property?  -1 means use the default baked into dotnet.native.js -->
-      <_WasmPThreadPoolSize Condition="'$(_WasmPThreadPoolSize)' == ''">-1</_WasmPThreadPoolSize>
+      <_WasmPThreadPoolInitialSize Condition="'$(_WasmPThreadPoolInitialSize)' == ''">-1</_WasmPThreadPoolInitialSize>
+      <_WasmPThreadPoolUnusedSize Condition="'$(_WasmPThreadPoolUnusedSize)' == ''">-1</_WasmPThreadPoolUnusedSize>
     </PropertyGroup>
 
     <ItemGroup>
@@ -148,7 +149,8 @@
       NativeAssets="@(WasmNativeAsset)"
       DebugLevel="$(WasmDebugLevel)"
       IncludeThreadsWorker="$(WasmEnableThreads)"
-      PThreadPoolSize="$(_WasmPThreadPoolSize)"
+      PThreadPoolInitialSize="$(_WasmPThreadPoolInitialSize)"
+      PThreadPoolUnusedSize="$(_WasmPThreadPoolUnusedSize)"
       UseWebcil="$(WasmEnableWebcil)"
       WasmIncludeFullIcuData="$(WasmIncludeFullIcuData)"
       WasmIcuDataFileName="$(WasmIcuDataFileName)"

src/mono/browser/runtime/assets.ts

@@ -1,13 +1,14 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+import type { AssetEntryInternal } from "./types/internal";
+
 import cwraps from "./cwraps";
 import { mono_wasm_load_icu_data } from "./icu";
 import { Module, loaderHelpers, mono_assert, runtimeHelpers } from "./globals";
 import { mono_log_info, mono_log_debug, parseSymbolMapFile } from "./logging";
 import { mono_wasm_load_bytes_into_heap } from "./memory";
 import { endMeasure, MeasuredBlock, startMeasure } from "./profiler";
-import { AssetEntryInternal } from "./types/internal";
 import { AssetEntry } from "./types";
 import { VoidPtr } from "./types/emscripten";
 import { setSegmentationRulesFromJson } from "./hybrid-globalization/grapheme-segmenter";

src/mono/browser/runtime/cwraps.ts

@@ -6,13 +6,12 @@ import WasmEnableThreads from "consts:wasmEnableThreads";
 import type {
     MonoAssembly, MonoClass,
     MonoMethod, MonoObject,
-    MonoType, MonoObjectRef, MonoStringRef, JSMarshalerArguments
+    MonoType, MonoObjectRef, MonoStringRef, JSMarshalerArguments, PThreadPtr
 } from "./types/internal";
 import type { VoidPtr, CharPtrPtr, Int32Ptr, CharPtr, ManagedPointer } from "./types/emscripten";
 import { Module, runtimeHelpers } from "./globals";
 import { mono_log_error } from "./logging";
 import { mono_assert } from "./globals";
-import { PThreadPtr } from "./pthreads/shared/types";
 
 type SigLine = [lazyOrSkip: boolean | (() => boolean), name: string, returnType: string | null, argTypes?: string[], opts?: any];
 

src/mono/browser/runtime/debug.ts

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 import BuildConfiguration from "consts:configuration";
+
 import { INTERNAL, Module, loaderHelpers, runtimeHelpers } from "./globals";
 import { toBase64StringImpl } from "./base64";
 import cwraps from "./cwraps";

src/mono/browser/runtime/diagnostics/browser/controller.ts

@@ -7,10 +7,10 @@ import { threads_c_functions as cwraps } from "../../cwraps";
 import { INTERNAL, mono_assert } from "../../globals";
 import { mono_log_info, mono_log_debug, mono_log_warn } from "../../logging";
 import { withStackAlloc, getI32 } from "../../memory";
-import { Thread, waitForThread } from "../../pthreads/browser";
+import { waitForThread } from "../../pthreads";
 import { isDiagnosticMessage, makeDiagnosticServerControlCommand } from "../shared/controller-commands";
 import monoDiagnosticsMock from "consts:monoDiagnosticsMock";
-import { PThreadPtr } from "../../pthreads/shared/types";
+import { PThreadPtr, Thread } from "../../types/internal";
 
 /// An object that can be used to control the diagnostic server.
 export interface ServerController {

src/mono/browser/runtime/diagnostics/index.ts

@@ -37,12 +37,9 @@ let diagnosticsServerEnabled = false;
 let diagnosticsInitialized = false;
 
 export async function mono_wasm_init_diagnostics(): Promise<void> {
-    if (diagnosticsInitialized)
-        return;
-    if (!WasmEnableThreads) {
-        mono_log_warn("ignoring diagnostics options because this runtime does not support diagnostics");
-        return;
-    }
+    if (!WasmEnableThreads) return;
+    if (diagnosticsInitialized) return;
+
     const options = diagnostic_options_from_environment();
     if (!options)
         return;

src/mono/browser/runtime/diagnostics/mock/environment.ts

@@ -6,7 +6,7 @@ import type { FilterPredicate, MockEnvironment } from "./types";
 import Serializer from "../server_pthread/ipc-protocol/base-serializer";
 import { CommandSetId, EventPipeCommandId, ProcessCommandId } from "../server_pthread/ipc-protocol/types";
 import { assertNever } from "../../types/internal";
-import { pthread_self } from "../../pthreads/worker";
+import { pthread_self } from "../../pthreads";
 import { createPromiseController, mono_assert } from "../../globals";
 
 

src/mono/browser/runtime/diagnostics/server_pthread/index.ts

@@ -6,7 +6,7 @@ import WasmEnableThreads from "consts:wasmEnableThreads";
 import monoDiagnosticsMock from "consts:monoDiagnosticsMock";
 
 import { PromiseAndController, assertNever } from "../../types/internal";
-import { pthread_self } from "../../pthreads/worker";
+import { pthread_self } from "../../pthreads";
 import { createPromiseController, mono_assert } from "../../globals";
 import { threads_c_functions as cwraps } from "../../cwraps";
 import { EventPipeSessionIDImpl } from "../shared/types";

src/mono/browser/runtime/diagnostics/shared/controller-commands.ts

@@ -1,8 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-import type { MonoThreadMessage } from "../../pthreads/shared";
-import { isMonoThreadMessage } from "../../pthreads/shared";
+import { isMonoThreadMessage } from "../../pthreads";
+import type { MonoThreadMessage } from "../../types/internal";
 
 // Messages from the main thread to the diagnostic server thread
 export interface DiagnosticMessage extends MonoThreadMessage {

src/mono/browser/runtime/dotnet.d.ts

@@ -189,7 +189,15 @@ type MonoConfig = {
     /**
      * initial number of workers to add to the emscripten pthread pool
      */
-    pthreadPoolSize?: number;
+    pthreadPoolInitialSize?: number;
+    /**
+     * number of unused workers kept in the emscripten pthread pool after startup
+     */
+    pthreadPoolUnusedSize?: number;
+    /**
+     * Delay in milliseconds before starting the finalizer thread
+     */
+    finalizerThreadStartDelayMs?: number;
     /**
      * If true, a list of the methods optimized by the interpreter will be saved and used for faster startup
      *  on future runs of the application

src/mono/browser/runtime/exports-binding.ts

@@ -10,8 +10,7 @@ import { mono_interp_tier_prepare_jiterpreter, mono_jiterp_free_method_data_js }
 import { mono_interp_jit_wasm_entry_trampoline, mono_interp_record_interp_entry } from "./jiterpreter-interp-entry";
 import { mono_interp_jit_wasm_jit_call_trampoline, mono_interp_invoke_wasm_jit_call_trampoline, mono_interp_flush_jitcall_queue } from "./jiterpreter-jit-call";
 import { mono_wasm_resolve_or_reject_promise } from "./marshal-to-js";
-import { mono_wasm_eventloop_has_unsettled_interop_promises } from "./pthreads/shared/eventloop";
-import { mono_wasm_pthread_on_pthread_attached, mono_wasm_pthread_on_pthread_unregistered, mono_wasm_pthread_on_pthread_registered, mono_wasm_pthread_set_name } from "./pthreads/worker";
+import { mono_wasm_eventloop_has_unsettled_interop_promises } from "./pthreads";
 import { mono_wasm_schedule_timer, schedule_background_exec } from "./scheduling";
 import { mono_wasm_asm_loaded } from "./startup";
 import { mono_wasm_diagnostic_server_on_server_thread_created } from "./diagnostics/server_pthread";
@@ -22,13 +21,15 @@ import { mono_wasm_profiler_leave, mono_wasm_profiler_enter } from "./profiler";
 import { mono_wasm_change_case, mono_wasm_change_case_invariant } from "./hybrid-globalization/change-case";
 import { mono_wasm_compare_string, mono_wasm_ends_with, mono_wasm_starts_with, mono_wasm_index_of } from "./hybrid-globalization/collations";
 import { mono_wasm_get_calendar_info } from "./hybrid-globalization/calendar";
-import { mono_wasm_install_js_worker_interop, mono_wasm_uninstall_js_worker_interop } from "./pthreads/shared";
 
 import { mono_wasm_get_culture_info } from "./hybrid-globalization/culture-info";
 import { mono_wasm_get_first_day_of_week, mono_wasm_get_first_week_of_year } from "./hybrid-globalization/locales";
 import { mono_wasm_browser_entropy } from "./crypto";
 import { mono_wasm_cancel_promise } from "./cancelable-promise";
 
+import { mono_wasm_pthread_on_pthread_attached, mono_wasm_pthread_on_pthread_unregistered, mono_wasm_pthread_on_pthread_registered, mono_wasm_pthread_set_name } from "./pthreads";
+import { mono_wasm_install_js_worker_interop, mono_wasm_uninstall_js_worker_interop } from "./pthreads";
+
 // the JS methods would be visible to EMCC linker and become imports of the WASM module
 
 export const mono_wasm_threads_imports = !WasmEnableThreads ? [] : [

src/mono/browser/runtime/exports-internal.ts

@@ -1,6 +1,9 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+import WasmEnableThreads from "consts:wasmEnableThreads";
+
+import { MonoObjectNull, type MonoObject } from "./types/internal";
 import cwraps, { profiler_c_functions } from "./cwraps";
 import { mono_wasm_send_dbg_command_with_parms, mono_wasm_send_dbg_command, mono_wasm_get_dbg_command_info, mono_wasm_get_details, mono_wasm_release_object, mono_wasm_call_function_on, mono_wasm_debugger_resume, mono_wasm_detach_debugger, mono_wasm_raise_debug_event, mono_wasm_change_debugger_log_level, mono_wasm_debugger_attached } from "./debug";
 import { http_wasm_supports_streaming_request, http_wasm_supports_streaming_response, http_wasm_create_controller, http_wasm_abort_request, http_wasm_abort_response, http_wasm_transform_stream_write, http_wasm_transform_stream_close, http_wasm_fetch, http_wasm_fetch_stream, http_wasm_fetch_bytes, http_wasm_get_response_header_names, http_wasm_get_response_header_values, http_wasm_get_response_bytes, http_wasm_get_response_length, http_wasm_get_streamed_response_bytes, http_wasm_get_response_type, http_wasm_get_response_status } from "./http";
@@ -17,16 +20,17 @@ import { loadLazyAssembly } from "./lazyLoading";
 import { loadSatelliteAssemblies } from "./satelliteAssemblies";
 import { forceDisposeProxies } from "./gc-handles";
 import { mono_wasm_get_func_id_to_name_mappings } from "./logging";
-import { MonoObject, MonoObjectNull } from "./types/internal";
 import { monoStringToStringUnsafe } from "./strings";
-import { thread_available } from "./pthreads/browser";
 import { mono_wasm_bind_cs_function } from "./invoke-cs";
 
+import { dumpThreads, thread_available } from "./pthreads";
+
 export function export_internal(): any {
     return {
         // tests
         mono_wasm_exit: (exit_code: number) => { Module.err("early exit " + exit_code); },
         forceDisposeProxies,
+        dumpThreads: WasmEnableThreads ? dumpThreads : undefined,
 
         // with mono_wasm_debugger_log and mono_wasm_trace_logger
         logging: undefined,
@@ -57,7 +61,7 @@ export function export_internal(): any {
         get_global_this,
         get_dotnet_instance: () => exportedRuntimeAPI,
         dynamic_import,
-        thread_available,
+        thread_available: WasmEnableThreads ? thread_available : undefined,
         mono_wasm_bind_cs_function,
 
         // BrowserWebSocket

src/mono/browser/runtime/exports.ts

@@ -22,7 +22,7 @@ import { mono_wasm_stringify_as_error_with_stack } from "./logging";
 import { instantiate_asset, instantiate_symbols_asset, instantiate_segmentation_rules_asset } from "./assets";
 import { jiterpreter_dump_stats } from "./jiterpreter";
 import { forceDisposeProxies } from "./gc-handles";
-import { dumpThreads } from "./pthreads/browser";
+import { dumpThreads } from "./pthreads";
 
 export let runtimeList: RuntimeList;
 

src/mono/browser/runtime/interp-pgo.ts

@@ -197,7 +197,9 @@ export async function getCacheKey(prefix: string): Promise<string | null> {
     delete inputs.interopCleanupOnExit;
     delete inputs.dumpThreadsOnNonZeroExit;
     delete inputs.logExitCode;
-    delete inputs.pthreadPoolSize;
+    delete inputs.pthreadPoolInitialSize;
+    delete inputs.pthreadPoolUnusedSize;
+    delete inputs.finalizerThreadStartDelayMs;
     delete inputs.asyncFlushOnExit;
     delete inputs.remoteSources;
     delete inputs.ignorePdbLoadErrors;

src/mono/browser/runtime/loader/assets.ts

@@ -3,7 +3,7 @@
 
 import WasmEnableThreads from "consts:wasmEnableThreads";
 
-import type { AssetEntryInternal, PromiseAndController } from "../types/internal";
+import { PThreadPtrNull, type AssetEntryInternal, type PThreadWorker, type PromiseAndController } from "../types/internal";
 import type { AssetBehaviors, AssetEntry, LoadingResource, ResourceList, SingleAssetBehaviors as SingleAssetBehaviors, WebAssemblyBootResourceType } from "../types";
 import { ENVIRONMENT_IS_NODE, ENVIRONMENT_IS_SHELL, ENVIRONMENT_IS_WEB, loaderHelpers, mono_assert, runtimeHelpers } from "./globals";
 import { createPromiseController } from "./promise-controller";
@@ -20,6 +20,9 @@ let parallel_count = 0;
 const assetsToLoad: AssetEntryInternal[] = [];
 const singleAssets: Map<string, AssetEntryInternal> = new Map();
 
+// A duplicate in pthreads/shared.ts
+const worker_empty_prefix = "          -    ";
+
 const jsRuntimeModulesAssetTypes: {
     [k: string]: boolean
 } = {
@@ -733,4 +736,24 @@ export async function streamingCompileWasm() {
     catch (err) {
         loaderHelpers.wasmCompilePromise.promise_control.reject(err);
     }
-}
+}
+
+export function preloadWorkers() {
+    if (!WasmEnableThreads) return;
+    const jsModuleWorker = resolve_single_asset_path("js-module-threads");
+    for (let i = 0; i < loaderHelpers.config.pthreadPoolInitialSize!; i++) {
+        const workerNumber = loaderHelpers.workerNextNumber++;
+        const worker: Partial<PThreadWorker> = new Worker(jsModuleWorker.resolvedUrl!, {
+            name: "dotnet-worker-" + workerNumber.toString().padStart(3, "0"),
+        });
+        worker.info = {
+            workerNumber,
+            pthreadId: PThreadPtrNull,
+            reuseCount: 0,
+            updateCount: 0,
+            threadPrefix: worker_empty_prefix,
+            threadName: "emscripten-pool",
+        } as any;
+        loaderHelpers.loadingWorkers.push(worker as any);
+    }
+}

src/mono/browser/runtime/loader/config.ts

@@ -187,9 +187,15 @@ export function normalizeConfig() {
         config.cachedResourcesPurgeDelay = 10000;
     }
 
-    if (WasmEnableThreads && !Number.isInteger(config.pthreadPoolSize)) {
-        // ActiveIssue https://github.com/dotnet/runtime/issues/75602
-        config.pthreadPoolSize = 7;
+    // ActiveIssue https://github.com/dotnet/runtime/issues/75602
+    if (WasmEnableThreads && !Number.isInteger(config.pthreadPoolInitialSize)) {
+        config.pthreadPoolInitialSize = 7;
+    }
+    if (WasmEnableThreads && !Number.isInteger(config.pthreadPoolUnusedSize)) {
+        config.pthreadPoolUnusedSize = 3;
+    }
+    if (WasmEnableThreads && !Number.isInteger(config.finalizerThreadStartDelayMs)) {
+        config.finalizerThreadStartDelayMs = 200;
     }
 
     // this is how long the Mono GC will try to wait for all threads to be suspended before it gives up and aborts the process

src/mono/browser/runtime/loader/globals.ts

@@ -92,6 +92,8 @@ export function setLoaderGlobals(
         loadedFiles: [],
         loadedAssemblies: [],
         libraryInitializers: [],
+        loadingWorkers: [],
+        workerNextNumber: 1,
         actual_downloaded_assets_count: 0,
         actual_instantiated_assets_count: 0,
         expected_downloaded_assets_count: 0,

src/mono/browser/runtime/loader/run.ts

@@ -10,7 +10,7 @@ import { ENVIRONMENT_IS_WEB, ENVIRONMENT_IS_WORKER, emscriptenModule, exportedRu
 import { deep_merge_config, deep_merge_module, mono_wasm_load_config } from "./config";
 import { installUnhandledErrorHandler, mono_exit, registerEmscriptenExitHandlers } from "./exit";
 import { setup_proxy_console, mono_log_info, mono_log_debug } from "./logging";
-import { mono_download_assets, prepareAssets, prepareAssetsWorker, resolve_single_asset_path, streamingCompileWasm } from "./assets";
+import { mono_download_assets, preloadWorkers, prepareAssets, prepareAssetsWorker, resolve_single_asset_path, streamingCompileWasm } from "./assets";
 import { detect_features_and_polyfill } from "./polyfills";
 import { runtimeHelpers, loaderHelpers } from "./globals";
 import { init_globalization } from "./icu";
@@ -487,6 +487,7 @@ async function createEmscriptenMain(): Promise<RuntimeAPI> {
     setTimeout(async () => {
         try {
             init_globalization();
+            preloadWorkers();
             await mono_download_assets();
         }
         catch (err) {

src/mono/browser/runtime/loader/worker.ts

@@ -1,10 +1,10 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-import { MonoConfigInternal, WorkerToMainMessageType, monoMessageSymbol } from "../types/internal";
+import { MonoConfigInternal, PThreadInfo, WorkerToMainMessageType, monoMessageSymbol } from "../types/internal";
 import { MonoConfig } from "../types";
 import { deep_merge_config, normalizeConfig } from "./config";
-import { ENVIRONMENT_IS_WEB, loaderHelpers } from "./globals";
+import { ENVIRONMENT_IS_WEB, loaderHelpers, runtimeHelpers } from "./globals";
 import { mono_log_debug } from "./logging";
 
 export function setupPreloadChannelToMainThread() {
@@ -13,7 +13,8 @@ export function setupPreloadChannelToMainThread() {
     const mainPort = channel.port2;
     workerPort.addEventListener("message", (event) => {
         const config = JSON.parse(event.data.config) as MonoConfig;
-        onMonoConfigReceived(config);
+        const monoThreadInfo = JSON.parse(event.data.monoThreadInfo) as PThreadInfo;
+        onMonoConfigReceived(config, monoThreadInfo);
         workerPort.close();
         mainPort.close();
     }, { once: true });
@@ -30,13 +31,13 @@ export function setupPreloadChannelToMainThread() {
 let workerMonoConfigReceived = false;
 
 // called when the main thread sends us the mono config
-function onMonoConfigReceived(config: MonoConfigInternal): void {
+function onMonoConfigReceived(config: MonoConfigInternal, monoThreadInfo: PThreadInfo): void {
     if (workerMonoConfigReceived) {
         mono_log_debug("mono config already received");
         return;
     }
-
     deep_merge_config(loaderHelpers.config, config);
+    runtimeHelpers.monoThreadInfo = monoThreadInfo;
     normalizeConfig();
     mono_log_debug("mono config received");
     workerMonoConfigReceived = true;

src/mono/browser/runtime/managed-exports.ts

@@ -11,7 +11,7 @@ import { marshal_array_to_cs, marshal_array_to_cs_impl, marshal_bool_to_cs, mars
 import { marshal_int32_to_js, end_marshal_task_to_js, marshal_string_to_js, begin_marshal_task_to_js, marshal_exception_to_js } from "./marshal-to-js";
 import { do_not_force_dispose } from "./gc-handles";
 import { assert_c_interop, assert_js_interop } from "./invoke-js";
-import { mono_wasm_main_thread_ptr } from "./pthreads/shared";
+import { mono_wasm_main_thread_ptr } from "./pthreads";
 import { _zero_region } from "./memory";
 import { stringToUTF8Ptr } from "./strings";
 

src/mono/browser/runtime/marshal-to-cs.ts

@@ -22,7 +22,7 @@ import { _zero_region, forceThreadMemoryViewRefresh, localHeapViewF64, localHeap
 import { stringToMonoStringRoot, stringToUTF16 } from "./strings";
 import { JSMarshalerArgument, JSMarshalerArguments, JSMarshalerType, MarshalerToCs, MarshalerToJs, BoundMarshalerToCs, MarshalerType } from "./types/internal";
 import { TypedArray } from "./types/emscripten";
-import { addUnsettledPromise, settleUnsettledPromise } from "./pthreads/shared/eventloop";
+import { addUnsettledPromise, settleUnsettledPromise } from "./pthreads";
 import { mono_log_debug } from "./logging";
 import { complete_task } from "./managed-exports";
 import { gc_locked } from "./gc-lock";