Use idle time to make progress on scheduled compilation jobs

src/compiler-dispatcher/compiler-dispatcher.cc

Index: src/compiler-dispatcher/compiler-dispatcher.cc
diff --git a/src/compiler-dispatcher/compiler-dispatcher.cc b/src/compiler-dispatcher/compiler-dispatcher.cc
index 8d503780cd5511b7af36cbbf865e6037277a5282..1b639fe9b0ad7035969b993a2253397461fa595c 100644
--- a/src/compiler-dispatcher/compiler-dispatcher.cc
+++ b/src/compiler-dispatcher/compiler-dispatcher.cc
@@ -4,6 +4,10 @@
 
 #include "src/compiler-dispatcher/compiler-dispatcher.h"
 
+#include "include/v8-platform.h"
+#include "include/v8.h"
+#include "src/base/platform/time.h"
+#include "src/cancelable-task.h"
 #include "src/compiler-dispatcher/compiler-dispatcher-job.h"
 #include "src/compiler-dispatcher/compiler-dispatcher-tracer.h"
 #include "src/objects-inl.h"
@@ -13,7 +17,12 @@ namespace internal {
 
 namespace {
 
-bool DoNextStepOnMainThread(CompilerDispatcherJob* job) {
+enum class ExceptionHandling { kSwallow, kThrow };
+
+bool DoNextStepOnMainThread(Isolate* isolate, CompilerDispatcherJob* job,
+                            ExceptionHandling exception_handling) {
+  DCHECK(ThreadId::Current().Equals(isolate->thread_id()));
+  v8::TryCatch try_catch(reinterpret_cast<v8::Isolate*>(isolate));
   switch (job->status()) {
     case CompileJobStatus::kInitial:
       job->PrepareToParseOnMainThread();
@@ -44,6 +53,11 @@ bool DoNextStepOnMainThread(CompilerDispatcherJob* job) {
       break;
   }
 
+  if (exception_handling == ExceptionHandling::kThrow &&
+      try_catch.HasCaught()) {
+    DCHECK(job->status() == CompileJobStatus::kFailed);
+    try_catch.ReThrow();
+  }
   return job->status() != CompileJobStatus::kFailed;
 }
 
@@ -52,14 +66,48 @@ bool IsFinished(CompilerDispatcherJob* job) {
          job->status() == CompileJobStatus::kFailed;
 }
 
+// Theoretically we get 50ms of idle time max, however it's unlikely that
+// we'll get all of it so try to be a conservative.
+const double kMaxIdleTimeToExpectInMs = 40;
+
 }  // namespace
 
-CompilerDispatcher::CompilerDispatcher(Isolate* isolate, size_t max_stack_size)
+class CompilerDispatcher::IdleTask : public CancelableIdleTask {
+ public:
+  IdleTask(Isolate* isolate, CompilerDispatcher* dispatcher);
+  ~IdleTask() override;
+
+  // CancelableIdleTask implementation.
+  void RunInternal(double deadline_in_seconds) override;
+
+ private:
+  CompilerDispatcher* dispatcher_;
+
+  DISALLOW_COPY_AND_ASSIGN(IdleTask);
+};
+
+CompilerDispatcher::IdleTask::IdleTask(Isolate* isolate,
+                                       CompilerDispatcher* dispatcher)
+    : CancelableIdleTask(isolate), dispatcher_(dispatcher) {}
+
+CompilerDispatcher::IdleTask::~IdleTask() {}
+
+void CompilerDispatcher::IdleTask::RunInternal(double deadline_in_seconds) {
+  dispatcher_->DoIdleWork(deadline_in_seconds);
+}
+
+CompilerDispatcher::CompilerDispatcher(Isolate* isolate, Platform* platform,
+                                       size_t max_stack_size)
     : isolate_(isolate),
+      platform_(platform),
       max_stack_size_(max_stack_size),
-      tracer_(new CompilerDispatcherTracer(isolate_)) {}
+      tracer_(new CompilerDispatcherTracer(isolate_)),
+      idle_task_scheduled_(false) {}
 
-CompilerDispatcher::~CompilerDispatcher() {}
+CompilerDispatcher::~CompilerDispatcher() {
+  // To avoid crashing in unit tests due to unfished jobs.
+  AbortAll(BlockingBehavior::kBlock);
+}
 
 bool CompilerDispatcher::Enqueue(Handle<SharedFunctionInfo> function) {
   // We only handle functions (no eval / top-level code / wasm) that are
@@ -75,6 +123,7 @@ bool CompilerDispatcher::Enqueue(Handle<SharedFunctionInfo> function) {
   std::pair<int, int> key(Script::cast(function->script())->id(),
                           function->function_literal_id());
   jobs_.insert(std::make_pair(key, std::move(job)));
+  ScheduleIdleTaskIfNeeded();
   return true;
 }
 
@@ -89,9 +138,11 @@ bool CompilerDispatcher::FinishNow(Handle<SharedFunctionInfo> function) {
   // TODO(jochen): Check if there's an in-flight background task working on this
   // job.
   while (!IsFinished(job->second.get())) {
-    DoNextStepOnMainThread(job->second.get());
+    DoNextStepOnMainThread(isolate_, job->second.get(),
+                           ExceptionHandling::kThrow);
   }
   bool result = job->second->status() != CompileJobStatus::kFailed;
+  job->second->ResetOnMainThread();
   jobs_.erase(job);
   return result;
 }
@@ -104,6 +155,7 @@ void CompilerDispatcher::Abort(Handle<SharedFunctionInfo> function,
 
   // TODO(jochen): Check if there's an in-flight background task working on this
   // job.
+  job->second->ResetOnMainThread();
   jobs_.erase(job);
 }
 
@@ -111,6 +163,9 @@ void CompilerDispatcher::AbortAll(BlockingBehavior blocking) {
   USE(blocking);
   // TODO(jochen): Check if there's an in-flight background task working on this
   // job.
+  for (auto& kv : jobs_) {
+    kv.second->ResetOnMainThread();
+  }
   jobs_.clear();
 }
 
@@ -126,5 +181,54 @@ CompilerDispatcher::JobMap::const_iterator CompilerDispatcher::GetJobFor(
   return jobs_.end();
 }
 
+void CompilerDispatcher::ScheduleIdleTaskIfNeeded() {
+  v8::Isolate* v8_isolate = reinterpret_cast<v8::Isolate*>(isolate_);
+  if (!platform_->IdleTasksEnabled(v8_isolate)) return;
+  if (idle_task_scheduled_) return;
+  if (jobs_.empty()) return;
+  idle_task_scheduled_ = true;
+  platform_->CallIdleOnForegroundThread(v8_isolate,
+                                        new IdleTask(isolate_, this));
+}
+
+void CompilerDispatcher::DoIdleWork(double deadline_in_seconds) {
+  idle_task_scheduled_ = false;
+
+  // Number of jobs that are unlikely to make progress during any idle callback
+  // due to their estimated duration.
+  size_t too_long_jobs = 0;
+
+  // Iterate over all available jobs & remaining time. For each job, decide
+  // whether to 1) skip it (if it would take too long), 2) erase it (if it's
+  // finished), or 3) make progress on it.
+  double idle_time_in_seconds =
+      deadline_in_seconds - platform_->MonotonicallyIncreasingTime();
+  for (auto job = jobs_.begin();
+       job != jobs_.end() && idle_time_in_seconds > 0.0;
+       idle_time_in_seconds =
+           deadline_in_seconds - platform_->MonotonicallyIncreasingTime()) {
+    double estimate_in_ms = job->second->EstimateRuntimeOfNextStepInMs();
+    if (idle_time_in_seconds <
+        (estimate_in_ms /
+         static_cast<double>(base::Time::kMillisecondsPerSecond))) {
+      // If there's not enough time left, try to estimate whether we would
+      // have managed to finish the job in a large idle task to assess
+      // whether we should ask for another idle callback.
+      if (estimate_in_ms > kMaxIdleTimeToExpectInMs) ++too_long_jobs;
+      ++job;
+    } else if (IsFinished(job->second.get())) {
+      job->second->ResetOnMainThread();
+      job = jobs_.erase(job);
+      break;
+    } else {
+      // Do one step, and keep processing the job (as we don't advance the
+      // iterator).
+      DoNextStepOnMainThread(isolate_, job->second.get(),
+                             ExceptionHandling::kSwallow);
+    }
+  }
+  if (jobs_.size() > too_long_jobs) ScheduleIdleTaskIfNeeded();
+}
+
 }  // namespace internal
 }  // namespace v8