[wasm] Remove support for compilation task throttling.

This removes support to track the memory footprint of fully executed but
not yet finalized compilation units. It was used to throttle creation of
new tasks when the latent memory pressure of this unfinished jobs rose
above a certain threshold. Now that units no longer incur a significant
latent memory pressure, this is no longer needed.

R=clemensh@chromium.org
BUG=v8:7921

Change-Id: I3f4a563ebcb85b7aeac50f469a8a495eecf8aa3d
Reviewed-on: https://chromium-review.googlesource.com/1136291
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54435}

src/compiler/wasm-compiler.cc

@@ -5232,10 +5232,6 @@ void TurbofanWasmCompilationUnit::ExecuteCompilation() {
     }
     if (ok_) wasm_code_ = info.wasm_code();
   }
-
-  // Record the memory cost this unit places on the system until
-  // it is finalized.
-  wasm_unit_->memory_cost_ = sizeof(TurbofanWasmCompilationUnit);
 }
 
 wasm::WasmCode* TurbofanWasmCompilationUnit::FinishCompilation(

src/wasm/baseline/liftoff-compiler.cc

@@ -1886,10 +1886,6 @@ bool LiftoffCompilationUnit::ExecuteCompilation() {
       wasm::WasmCode::kLiftoff);
   wasm_unit_->native_module_->PublishCode(code_);
 
-  // Record the memory cost this unit places on the system until
-  // it is finalized.
-  wasm_unit_->memory_cost_ = sizeof(*this);
-
   return true;
 }
 

src/wasm/function-compiler.h

@@ -76,7 +76,6 @@ class WasmCompilationUnit final {
       Isolate* isolate, ModuleEnv* env, const wasm::WasmFunction* function,
       CompilationMode = GetDefaultCompilationMode());
 
-  size_t memory_cost() const { return memory_cost_; }
   wasm::NativeModule* native_module() const { return native_module_; }
   CompilationMode mode() const { return mode_; }
 
@@ -90,7 +89,6 @@ class WasmCompilationUnit final {
   wasm::WasmName func_name_;
   Counters* counters_;
   int func_index_;
-  size_t memory_cost_ = 0;
   wasm::NativeModule* native_module_;
   // TODO(wasm): Put {lower_simd_} inside the {ModuleEnv}.
   bool lower_simd_;

src/wasm/module-compiler.cc

@@ -95,8 +95,6 @@ class CompilationState {
   bool SetFinisherIsRunning(bool value);
   void ScheduleFinisherTask();
 
-  bool StopBackgroundCompilationTaskForThrottling();
-
   void Abort();
 
   Isolate* isolate() const { return isolate_; }
@@ -127,7 +125,6 @@ class CompilationState {
   WasmEngine* const wasm_engine_;
   // TODO(clemensh): Remove ModuleEnv, generate it when needed.
   ModuleEnv module_env_;
-  const size_t max_memory_;
   const CompileMode compile_mode_;
   bool baseline_compilation_finished_ = false;
 
@@ -148,8 +145,6 @@ class CompilationState {
   std::vector<std::unique_ptr<WasmCompilationUnit>> baseline_finish_units_;
   std::vector<std::unique_ptr<WasmCompilationUnit>> tiering_finish_units_;
 
-  size_t allocated_memory_ = 0;
-
   // End of fields protected by {mutex_}.
   //////////////////////////////////////////////////////////////////////////////
 
@@ -464,12 +459,6 @@ ModuleEnv CreateDefaultModuleEnv(const WasmModule* module,
   return ModuleEnv(module, use_trap_handler, kRuntimeExceptionSupport);
 }
 
-size_t GetMaxUsableMemorySize(Isolate* isolate) {
-  return isolate->heap()->memory_allocator()->code_range()->valid()
-             ? isolate->heap()->memory_allocator()->code_range()->size()
-             : isolate->heap()->code_space()->Capacity();
-}
-
 // The CompilationUnitBuilder builds compilation units and stores them in an
 // internal buffer. The buffer is moved into the working queue of the
 // CompilationState when {Commit} is called.
@@ -863,16 +852,14 @@ class BackgroundCompileTask : public CancelableTask {
 
   void RunInternal() override {
     TRACE_COMPILE("(3b) Compiling...\n");
-    // The number of currently running background tasks is reduced either in
+    // The number of currently running background tasks is reduced in
-    // {StopBackgroundCompilationTaskForThrottling} or in
     // {OnBackgroundTaskStopped}.
-    while (!compilation_state_->StopBackgroundCompilationTaskForThrottling()) {
+    while (!compilation_state_->failed()) {
-      if (compilation_state_->failed() ||
+      if (!FetchAndExecuteCompilationUnit(compilation_state_)) {
-          !FetchAndExecuteCompilationUnit(compilation_state_)) {
-        compilation_state_->OnBackgroundTaskStopped();
         break;
       }
     }
+    compilation_state_->OnBackgroundTaskStopped();
   }
 
  private:
@@ -2769,14 +2756,12 @@ CompilationState::CompilationState(internal::Isolate* isolate,
     : isolate_(isolate),
       wasm_engine_(isolate->wasm_engine()),
       module_env_(env),
-      max_memory_(GetMaxUsableMemorySize(isolate) / 2),
       compile_mode_(FLAG_wasm_tier_up && env.module->origin == kWasmOrigin
                         ? CompileMode::kTiering
                         : CompileMode::kRegular),
       max_background_tasks_(std::max(
           1, std::min(FLAG_wasm_num_compilation_tasks,
                       V8::GetCurrentPlatform()->NumberOfWorkerThreads()))) {
-  DCHECK_LT(0, max_memory_);
   v8::Isolate* v8_isolate = reinterpret_cast<v8::Isolate*>(isolate_);
   v8::Platform* platform = V8::GetCurrentPlatform();
   foreground_task_runner_ = platform->GetForegroundTaskRunner(v8_isolate);
@@ -2858,7 +2843,6 @@ std::unique_ptr<WasmCompilationUnit> CompilationState::GetNextExecutedUnit() {
   if (units.empty()) return {};
   std::unique_ptr<WasmCompilationUnit> ret = std::move(units.back());
   units.pop_back();
-  allocated_memory_ -= ret->memory_cost();
   return ret;
 }
 
@@ -2907,7 +2891,6 @@ void CompilationState::OnFinishedUnit() {
 void CompilationState::ScheduleUnitForFinishing(
     std::unique_ptr<WasmCompilationUnit> unit,
     WasmCompilationUnit::CompilationMode mode) {
-  size_t cost = unit->memory_cost();
   base::LockGuard<base::Mutex> guard(&mutex_);
   if (compile_mode_ == CompileMode::kTiering &&
       mode == WasmCompilationUnit::CompilationMode::kTurbofan) {
@@ -2915,7 +2898,6 @@ void CompilationState::ScheduleUnitForFinishing(
   } else {
     baseline_finish_units_.push_back(std::move(unit));
   }
-  allocated_memory_ += cost;
 
   if (!finisher_is_running_ && !failed_) {
     ScheduleFinisherTask();
@@ -2942,8 +2924,6 @@ void CompilationState::RestartBackgroundTasks(size_t max) {
     // No need to restart tasks if compilation already failed.
     if (failed_) return;
 
-    bool should_increase_workload = allocated_memory_ <= max_memory_ / 2;
-    if (!should_increase_workload) return;
     DCHECK_LE(num_background_tasks_, max_background_tasks_);
     if (num_background_tasks_ == max_background_tasks_) return;
     size_t num_compilation_units =
@@ -2979,15 +2959,6 @@ void CompilationState::ScheduleFinisherTask() {
       base::make_unique<FinishCompileTask>(this, &foreground_task_manager_));
 }
 
-bool CompilationState::StopBackgroundCompilationTaskForThrottling() {
-  base::LockGuard<base::Mutex> guard(&mutex_);
-  DCHECK_LE(1, num_background_tasks_);
-  bool can_accept_work = allocated_memory_ < max_memory_;
-  if (can_accept_work) return false;
-  --num_background_tasks_;
-  return true;
-}
-
 void CompilationState::Abort() {
   {
     base::LockGuard<base::Mutex> guard(&mutex_);