dart_vm.cc

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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#include "flutter/runtime/dart_vm.h"
 
#include <sys/stat.h>
 
#include <sstream>
#include <vector>
 
#include "flutter/common/settings.h"
#include "flutter/fml/cpu_affinity.h"
#include "flutter/fml/logging.h"
#include "flutter/fml/mapping.h"
#include "flutter/fml/time/time_delta.h"
#include "flutter/fml/trace_event.h"
#include "flutter/lib/ui/dart_ui.h"
#include "flutter/runtime/dart_isolate.h"
#include "flutter/runtime/dart_vm_initializer.h"
#include "flutter/runtime/ptrace_check.h"
#include "third_party/dart/runtime/include/bin/dart_io_api.h"
#include "third_party/skia/include/core/SkExecutor.h"
#include "third_party/tonic/converter/dart_converter.h"
#include "third_party/tonic/dart_class_library.h"
#include "third_party/tonic/dart_class_provider.h"
#include "third_party/tonic/file_loader/file_loader.h"
#include "third_party/tonic/logging/dart_error.h"
#include "third_party/tonic/typed_data/typed_list.h"
 
namespace flutter {
 
// Arguments passed to the Dart VM in all configurations.
static const char* kDartAllConfigsArgs[] = {
    // clang-format off
    "--enable_mirrors=false",
    "--background_compilation",
    // 'mark_when_idle' appears to cause a regression, turning off for now.
    // "--mark_when_idle",
    // clang-format on
};
 
static const char* kDartPrecompilationArgs[] = {"--precompilation"};
 
static const char* kSerialGCArgs[] = {
    // clang-format off
    "--concurrent_mark=false",
    "--concurrent_sweep=false",
    "--compactor_tasks=1",
    "--scavenger_tasks=0",
    "--marker_tasks=0",
    // clang-format on
};
 
[[maybe_unused]]
static const char* kDartWriteProtectCodeArgs[] = {
    "--no_write_protect_code",
};
 
[[maybe_unused]]
static const char* kDartDisableIntegerDivisionArgs[] = {
    "--no_use_integer_division",
};
 
static const char* kDartAssertArgs[] = {
    // clang-format off
    "--enable_asserts",
    // clang-format on
};
 
static const char* kDartStartPausedArgs[]{
    "--pause_isolates_on_start",
};
 
static const char* kDartEndlessTraceBufferArgs[]{
    "--timeline_recorder=endless",
};
 
static const char* kDartSystraceTraceBufferArgs[] = {
    "--timeline_recorder=systrace",
};
 
static std::string DartFileRecorderArgs(const std::string& path) {
  std::ostringstream oss;
  oss << "--timeline_recorder=perfettofile:" << path;
  return oss.str();
}
 
// "Microtask" is included in all argument strings below, but "Microtask" stream
// events will only be recorded by the VM's timeline recorders when
// |Switch::ProfileMicrotasks| is set.
 
[[maybe_unused]]
static const char* kDartDefaultTraceStreamsArgs[]{
    "--timeline_streams=Dart,Embedder,GC,Microtask",
};
 
static const char* kDartStartupTraceStreamsArgs[]{
    "--timeline_streams=Compiler,Dart,Debugger,Embedder,GC,Isolate,Microtask,"
    "VM,API",
};
 
static const char* kDartSystraceTraceStreamsArgs[] = {
    "--timeline_streams=Compiler,Dart,Debugger,Embedder,GC,Isolate,Microtask,"
    "VM,API",
};
 
static const char* kDartProfileMicrotasksArgs[]{
    "--profile_microtasks",
};
 
static std::string DartOldGenHeapSizeArgs(uint64_t heap_size) {
  std::ostringstream oss;
  oss << "--old_gen_heap_size=" << heap_size;
  return oss.str();
}
 
constexpr char kFileUriPrefix[] = "file://";
constexpr size_t kFileUriPrefixLength = sizeof(kFileUriPrefix) - 1;
 
bool DartFileModifiedCallback(const char* source_url, int64_t since_ms) {
  if (strncmp(source_url, kFileUriPrefix, kFileUriPrefixLength) != 0u) {
    // Assume modified.
    return true;
  }
 
  const char* path = source_url + kFileUriPrefixLength;
  struct stat info;
  if (stat(path, &info) < 0) {
    return true;
  }
 
  // If st_mtime is zero, it's more likely that the file system doesn't support
  // mtime than that the file was actually modified in the 1970s.
  if (!info.st_mtime) {
    return true;
  }
 
  // It's very unclear what time bases we're with here. The Dart API doesn't
  // document the time base for since_ms. Reading the code, the value varies by
  // platform, with a typical source being something like gettimeofday.
  //
  // We add one to st_mtime because st_mtime has less precision than since_ms
  // and we want to treat the file as modified if the since time is between
  // ticks of the mtime.
  fml::TimeDelta mtime = fml::TimeDelta::FromSeconds(info.st_mtime + 1);
  fml::TimeDelta since = fml::TimeDelta::FromMilliseconds(since_ms);
 
  return mtime > since;
}
 
void ThreadExitCallback() {}
 
static const char kStdoutStreamId[] = "Stdout";
static const char kStderrStreamId[] = "Stderr";
 
static bool ServiceStreamListenCallback(const char* stream_id) {
  if (strcmp(stream_id, kStdoutStreamId) == 0) {
    dart::bin::SetCaptureStdout(true);
    return true;
  } else if (strcmp(stream_id, kStderrStreamId) == 0) {
    dart::bin::SetCaptureStderr(true);
    return true;
  }
  return false;
}
 
static void ServiceStreamCancelCallback(const char* stream_id) {
  if (strcmp(stream_id, kStdoutStreamId) == 0) {
    dart::bin::SetCaptureStdout(false);
  } else if (strcmp(stream_id, kStderrStreamId) == 0) {
    dart::bin::SetCaptureStderr(false);
  }
}
 
bool DartVM::IsRunningPrecompiledCode() {
  return Dart_IsPrecompiledRuntime();
}
 
static std::vector<const char*> ProfilingFlags(bool enable_profiling,
                                               bool profile_startup) {
// Disable Dart's built in profiler when building a debug build. This
// works around a race condition that would sometimes stop a crash's
// stack trace from being printed on Android.
#ifndef NDEBUG
  enable_profiling = false;
#endif
 
  // We want to disable profiling by default because it overwhelms LLDB. But
  // the VM enables the same by default. In either case, we have some profiling
  // flags.
  if (enable_profiling) {
    std::vector<const char*> flags = {
        // This is the default. But just be explicit.
        "--profiler",
        // This instructs the profiler to walk C++ frames, and to include
        // them in the profile.
        "--profile-vm",
#if FML_OS_IOS && FML_ARCH_CPU_ARM_FAMILY && FML_ARCH_CPU_ARMEL
        // Set the profiler interrupt period to 500Hz instead of the
        // default 1000Hz on 32-bit iOS devices to reduce average and worst
        // case frame build times.
        //
        // Note: profile_period is time in microseconds between sampling
        // events, not frequency. Frequency is calculated 1/period (or
        // 1,000,000 / 2,000 -> 500Hz in this case).
        "--profile_period=2000",
#else
        "--profile_period=1000",
#endif  // FML_OS_IOS && FML_ARCH_CPU_ARM_FAMILY && FML_ARCH_CPU_ARMEL
    };
 
    if (profile_startup) {
      // This instructs the profiler to discard new samples once the profiler
      // sample buffer is full. When this flag is not set, the profiler sample
      // buffer is used as a ring buffer, meaning that once it is full, new
      // samples start overwriting the oldest ones."
      flags.push_back("--profile_startup");
    }
 
    return flags;
  } else {
    return {"--no-profiler"};
  }
}
 
void PushBackAll(std::vector<const char*>* args,
                 const char** argv,
                 size_t argc) {
  for (size_t i = 0; i < argc; ++i) {
    args->push_back(argv[i]);
  }
}
 
static void EmbedderInformationCallback(Dart_EmbedderInformation* info) {
  info->version = DART_EMBEDDER_INFORMATION_CURRENT_VERSION;
  dart::bin::GetIOEmbedderInformation(info);
  info->name = "Flutter";
}
 
std::shared_ptr<DartVM> DartVM::Create(
    const Settings& settings,
    fml::RefPtr<const DartSnapshot> vm_snapshot,
    fml::RefPtr<const DartSnapshot> isolate_snapshot,
    std::shared_ptr<IsolateNameServer> isolate_name_server) {
  auto vm_data = DartVMData::Create(settings,                    //
                                    std::move(vm_snapshot),      //
                                    std::move(isolate_snapshot)  //
  );
 
  if (!vm_data) {
    FML_LOG(ERROR) << "Could not set up VM data to bootstrap the VM from.";
    return {};
  }
 
  // Note: std::make_shared unviable due to hidden constructor.
  return std::shared_ptr<DartVM>(
      new DartVM(vm_data, std::move(isolate_name_server)));
}
 
static std::atomic_size_t gVMLaunchCount;
 
size_t DartVM::GetVMLaunchCount() {
  return gVMLaunchCount;
}
 
// Minimum and maximum number of worker threads.
static constexpr size_t kMinCount = 2;
static constexpr size_t kMaxCount = 4;
 
DartVM::DartVM(const std::shared_ptr<const DartVMData>& vm_data,
               std::shared_ptr<IsolateNameServer> isolate_name_server)
    : settings_(vm_data->GetSettings()),
      concurrent_message_loop_(fml::ConcurrentMessageLoop::Create(
          std::clamp(fml::EfficiencyCoreCount().value_or(
                         std::thread::hardware_concurrency()) /
                         2,
                     kMinCount,
                     kMaxCount))),
      skia_concurrent_executor_(
          [runner = concurrent_message_loop_->GetTaskRunner()](
              const fml::closure& work) { runner->PostTask(work); }),
      vm_data_(vm_data),
      isolate_name_server_(std::move(isolate_name_server)),
      service_protocol_(std::make_shared<ServiceProtocol>()) {
  TRACE_EVENT0("flutter", "DartVMInitializer");
 
  gVMLaunchCount++;
 
  // Setting the executor is not thread safe but Dart VM initialization is. So
  // this call is thread-safe.
  SkExecutor::SetDefault(&skia_concurrent_executor_);
 
  FML_DCHECK(vm_data_);
  FML_DCHECK(isolate_name_server_);
  FML_DCHECK(service_protocol_);
 
  {
    TRACE_EVENT0("flutter", "dart::bin::BootstrapDartIo");
    dart::bin::BootstrapDartIo();
 
    if (!settings_.temp_directory_path.empty()) {
      dart::bin::SetSystemTempDirectory(settings_.temp_directory_path.c_str());
    }
  }
 
  std::vector<const char*> args;
 
  // Instruct the VM to ignore unrecognized flags.
  // There is a lot of diversity in a lot of combinations when it
  // comes to the arguments the VM supports. And, if the VM comes across a flag
  // it does not recognize, it exits immediately.
  args.push_back("--ignore-unrecognized-flags");
 
  for (auto* const profiler_flag : ProfilingFlags(
           settings_.enable_dart_profiling, settings_.profile_startup)) {
    args.push_back(profiler_flag);
  }
 
  PushBackAll(&args, kDartAllConfigsArgs, std::size(kDartAllConfigsArgs));
 
  if (IsRunningPrecompiledCode()) {
    PushBackAll(&args, kDartPrecompilationArgs,
                std::size(kDartPrecompilationArgs));
  }
 
  // Enable Dart assertions if we are not running precompiled code. We run non-
  // precompiled code only in the debug product mode.
  bool enable_asserts = !settings_.disable_dart_asserts;
 
#if !OS_FUCHSIA
  if (IsRunningPrecompiledCode()) {
    enable_asserts = false;
  }
#endif  // !OS_FUCHSIA
 
#if (FLUTTER_RUNTIME_MODE == FLUTTER_RUNTIME_MODE_DEBUG)
#if !FML_OS_IOS && !FML_OS_MACOSX
  // Debug mode uses the JIT, disable code page write protection to avoid
  // memory page protection changes before and after every compilation.
  PushBackAll(&args, kDartWriteProtectCodeArgs,
              std::size(kDartWriteProtectCodeArgs));
#else
  const bool tracing_result = EnableTracingIfNecessary(settings_);
  // This check should only trip if the embedding made no attempts to enable
  // tracing. At this point, it is too late display user visible messages. Just
  // log and die.
  FML_CHECK(tracing_result)
      << "Tracing not enabled before attempting to run JIT mode VM.";
#if TARGET_CPU_ARM
  // Tell Dart in JIT mode to not use integer division on armv7
  // Ideally, this would be detected at runtime by Dart.
  // TODO(dnfield): Remove this code
  // https://github.com/dart-lang/sdk/issues/24743
  PushBackAll(&args, kDartDisableIntegerDivisionArgs,
              std::size(kDartDisableIntegerDivisionArgs));
#endif  // TARGET_CPU_ARM
#endif  // !FML_OS_IOS && !FML_OS_MACOSX
#endif  // (FLUTTER_RUNTIME_MODE == FLUTTER_RUNTIME_MODE_DEBUG)
 
  if (enable_asserts) {
    PushBackAll(&args, kDartAssertArgs, std::size(kDartAssertArgs));
  }
 
  // On low power devices with lesser number of cores, using concurrent
  // marking or sweeping causes contention for the UI thread leading to
  // Jank, this option can be used to turn off all concurrent GC activities.
  if (settings_.enable_serial_gc) {
    PushBackAll(&args, kSerialGCArgs, std::size(kSerialGCArgs));
  }
 
  if (settings_.start_paused) {
    PushBackAll(&args, kDartStartPausedArgs, std::size(kDartStartPausedArgs));
  }
 
  if (settings_.endless_trace_buffer || settings_.trace_startup) {
    // If we are tracing startup, make sure the trace buffer is endless so we
    // don't lose early traces.
    PushBackAll(&args, kDartEndlessTraceBufferArgs,
                std::size(kDartEndlessTraceBufferArgs));
  }
 
  if (settings_.trace_systrace) {
    PushBackAll(&args, kDartSystraceTraceBufferArgs,
                std::size(kDartSystraceTraceBufferArgs));
    PushBackAll(&args, kDartSystraceTraceStreamsArgs,
                std::size(kDartSystraceTraceStreamsArgs));
  }
 
  std::string file_recorder_args;
  if (!settings_.trace_to_file.empty()) {
    file_recorder_args = DartFileRecorderArgs(settings_.trace_to_file);
    args.push_back(file_recorder_args.c_str());
    PushBackAll(&args, kDartSystraceTraceStreamsArgs,
                std::size(kDartSystraceTraceStreamsArgs));
  }
 
  if (settings_.trace_startup) {
    PushBackAll(&args, kDartStartupTraceStreamsArgs,
                std::size(kDartStartupTraceStreamsArgs));
  }
 
#if defined(OS_FUCHSIA)
  PushBackAll(&args, kDartSystraceTraceBufferArgs,
              std::size(kDartSystraceTraceBufferArgs));
  PushBackAll(&args, kDartSystraceTraceStreamsArgs,
              std::size(kDartSystraceTraceStreamsArgs));
#else
  if (!settings_.trace_systrace && !settings_.trace_startup) {
    PushBackAll(&args, kDartDefaultTraceStreamsArgs,
                std::size(kDartDefaultTraceStreamsArgs));
  }
#endif  // defined(OS_FUCHSIA)
 
  if (settings_.profile_microtasks) {
    PushBackAll(&args, kDartProfileMicrotasksArgs,
                std::size(kDartProfileMicrotasksArgs));
  }
 
  std::string old_gen_heap_size_args;
  if (settings_.old_gen_heap_size >= 0) {
    old_gen_heap_size_args =
        DartOldGenHeapSizeArgs(settings_.old_gen_heap_size);
    args.push_back(old_gen_heap_size_args.c_str());
  }
 
  for (size_t i = 0; i < settings_.dart_flags.size(); i++) {
    args.push_back(settings_.dart_flags[i].c_str());
  }
 
  char* flags_error = Dart_SetVMFlags(args.size(), args.data());
  if (flags_error) {
    FML_LOG(FATAL) << "Error while setting Dart VM flags: " << flags_error;
    ::free(flags_error);
  }
 
  dart::bin::SetExecutableName(settings_.executable_name.c_str());
 
  {
    TRACE_EVENT0("flutter", "Dart_Initialize");
    Dart_InitializeParams params = {};
    params.version = DART_INITIALIZE_PARAMS_CURRENT_VERSION;
    params.vm_snapshot_data = vm_data_->GetVMSnapshot().GetDataMapping();
    params.vm_snapshot_instructions =
        vm_data_->GetVMSnapshot().GetInstructionsMapping();
    params.create_group = reinterpret_cast<decltype(params.create_group)>(
        DartIsolate::DartIsolateGroupCreateCallback);
    params.initialize_isolate =
        reinterpret_cast<decltype(params.initialize_isolate)>(
            DartIsolate::DartIsolateInitializeCallback);
    params.shutdown_isolate =
        reinterpret_cast<decltype(params.shutdown_isolate)>(
            DartIsolate::DartIsolateShutdownCallback);
    params.cleanup_isolate = reinterpret_cast<decltype(params.cleanup_isolate)>(
        DartIsolate::DartIsolateCleanupCallback);
    params.cleanup_group = reinterpret_cast<decltype(params.cleanup_group)>(
        DartIsolate::DartIsolateGroupCleanupCallback);
    params.thread_exit = ThreadExitCallback;
    params.file_open = dart::bin::OpenFile;
    params.file_read = dart::bin::ReadFile;
    params.file_write = dart::bin::WriteFile;
    params.file_close = dart::bin::CloseFile;
    params.entropy_source = dart::bin::GetEntropy;
    DartVMInitializer::Initialize(&params,
                                  settings_.enable_timeline_event_handler,
                                  settings_.trace_systrace);
    // Send the earliest available timestamp in the application lifecycle to
    // timeline. The difference between this timestamp and the time we render
    // the very first frame gives us a good idea about Flutter's startup time.
    // Use an instant event because the call to Dart_TimelineGetMicros
    // may behave differently before and after the Dart VM is initialized.
    // As this call is immediately after initialization of the Dart VM,
    // we are interested in only one timestamp.
    int64_t micros = Dart_TimelineGetMicros();
    Dart_RecordTimelineEvent("FlutterEngineMainEnter",  // label
                             micros,                    // timestamp0
                             micros,   // timestamp1_or_async_id
                             0,        // flow_id_count
                             nullptr,  // flow_ids
                             Dart_Timeline_Event_Instant,  // event type
                             0,                            // argument_count
                             nullptr,                      // argument_names
                             nullptr                       // argument_values
    );
  }
 
  Dart_SetFileModifiedCallback(&DartFileModifiedCallback);
 
  // Allow streaming of stdout and stderr by the Dart vm.
  Dart_SetServiceStreamCallbacks(&ServiceStreamListenCallback,
                                 &ServiceStreamCancelCallback);
 
  Dart_SetEmbedderInformationCallback(&EmbedderInformationCallback);
 
  if (settings_.dart_library_sources_kernel != nullptr) {
    std::unique_ptr<fml::Mapping> dart_library_sources =
        settings_.dart_library_sources_kernel();
    // Set sources for dart:* libraries for debugging.
    Dart_SetDartLibrarySourcesKernel(dart_library_sources->GetMapping(),
                                     dart_library_sources->GetSize());
  }
 
  // Update thread names now that the Dart VM is initialized.
  concurrent_message_loop_->PostTaskToAllWorkers(
      [] { Dart_SetThreadName("FlutterConcurrentMessageLoopWorker"); });
}
 
DartVM::~DartVM() {
  // Setting the executor is not thread safe but Dart VM shutdown is. So
  // this call is thread-safe.
  SkExecutor::SetDefault(nullptr);
 
  if (Dart_CurrentIsolate() != nullptr) {
    Dart_ExitIsolate();
  }
 
  DartVMInitializer::Cleanup();
 
  dart::bin::CleanupDartIo();
}
 
std::shared_ptr<const DartVMData> DartVM::GetVMData() const {
  return vm_data_;
}
 
const Settings& DartVM::GetSettings() const {
  return settings_;
}
 
std::shared_ptr<ServiceProtocol> DartVM::GetServiceProtocol() const {
  return service_protocol_;
}
 
std::shared_ptr<IsolateNameServer> DartVM::GetIsolateNameServer() const {
  return isolate_name_server_;
}
 
std::shared_ptr<fml::ConcurrentTaskRunner>
DartVM::GetConcurrentWorkerTaskRunner() const {
  return concurrent_message_loop_->GetTaskRunner();
}
 
std::shared_ptr<fml::ConcurrentMessageLoop> DartVM::GetConcurrentMessageLoop() {
  return concurrent_message_loop_;
}
 
}  // namespace flutter