memory-infra: Add peak-detector skeleton.

base/trace_event/memory_peak_detector.cc

Index: base/trace_event/memory_peak_detector.cc
diff --git a/base/trace_event/memory_peak_detector.cc b/base/trace_event/memory_peak_detector.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c361037c2d800540edbcf72ee2bbd415e1d69fab
--- /dev/null
+++ b/base/trace_event/memory_peak_detector.cc
@@ -0,0 +1,164 @@
+// Copyright 2017 The Chromium 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 "base/trace_event/memory_peak_detector.h"
+
+#include <stdint.h>
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "base/threading/sequenced_task_runner_handle.h"
+#include "base/time/time.h"
+#include "base/trace_event/memory_dump_provider_info.h"
+
+namespace base {
+namespace trace_event {
+
+// static
+MemoryPeakDetector* MemoryPeakDetector::GetInstance() {
+  static MemoryPeakDetector* instance = new MemoryPeakDetector();
+  return instance;
+}
+
+MemoryPeakDetector::MemoryPeakDetector()
+    : generation_(0),
+      state_(NOT_INITIALIZED),
+      polling_interval_ms_(0),
+      poll_tasks_count_for_testing_(0) {}
+
+MemoryPeakDetector::~MemoryPeakDetector() {
+  // This is hit only in tests, in which case the test is expected to TearDown()
+  // cleanly and not leave the peak detector running.
+  DCHECK_EQ(NOT_INITIALIZED, state_);
+}
+
+void MemoryPeakDetector::Setup(
+    const GetDumpProvidersFunction& get_dump_providers_function,
+    const scoped_refptr<SequencedTaskRunner>& task_runner,
+    const OnPeakDetectedCallback& on_peak_detected_callback) {
+  DCHECK(!get_dump_providers_function.is_null());
+  DCHECK(task_runner);
+  DCHECK(!on_peak_detected_callback.is_null());
+  DCHECK(state_ == NOT_INITIALIZED || state_ == DISABLED);
+  DCHECK(dump_providers_.empty());
+  get_dump_providers_function_ = get_dump_providers_function;
+  task_runner_ = task_runner;
+  on_peak_detected_callback_ = on_peak_detected_callback;
+  state_ = DISABLED;
+}
+
+void MemoryPeakDetector::TearDown() {
+  if (task_runner_) {
+    task_runner_->PostTask(
+        FROM_HERE,
+        Bind(&MemoryPeakDetector::TearDownInternal, Unretained(this)));
+  }
+  task_runner_ = nullptr;
+}
+
+void MemoryPeakDetector::Start() {
+  task_runner_->PostTask(
+      FROM_HERE, Bind(&MemoryPeakDetector::StartInternal, Unretained(this)));
+}
+
+void MemoryPeakDetector::Stop() {
+  task_runner_->PostTask(
+      FROM_HERE, Bind(&MemoryPeakDetector::StopInternal, Unretained(this)));
+}
+
+void MemoryPeakDetector::NotifyMemoryDumpProvidersChanged() {
+  // It is possible to call this before the first Setup() call, in which case
+  // we want to just make this a noop. The next Start() will fetch the MDP list.
+  if (!task_runner_)
+    return;
+  task_runner_->PostTask(
+      FROM_HERE,
+      Bind(&MemoryPeakDetector::ReloadDumpProvidersAndStartPollingIfNeeded,
+           Unretained(this)));
+}
+
+void MemoryPeakDetector::StartInternal() {
+  DCHECK_EQ(DISABLED, state_);
+  state_ = ENABLED;
+  polling_interval_ms_ = 1;  // TODO(primiano): temporary until next CL.
+
+  // If there are any dump providers available, NotifyMemoryDumpProvidersChanged
+  // will fetch them and start the polling. Otherwise this will remain in the
+  // ENABLED state and the actual polling will start on the next call to
+  // ReloadDumpProvidersAndStartPollingIfNeeded().
+  // Depending on the sandbox model, it is possible that no polling-capable dump
+  // providers will be ever available.
+  ReloadDumpProvidersAndStartPollingIfNeeded();
+}
+
+void MemoryPeakDetector::StopInternal() {
+  DCHECK_NE(NOT_INITIALIZED, state_);
+  state_ = DISABLED;
+  ++generation_;
+  dump_providers_.clear();
+}
+
+void MemoryPeakDetector::TearDownInternal() {
+  StopInternal();
+  get_dump_providers_function_.Reset();
+  on_peak_detected_callback_.Reset();
+  state_ = NOT_INITIALIZED;
+}
+
+void MemoryPeakDetector::ReloadDumpProvidersAndStartPollingIfNeeded() {
+  if (state_ == DISABLED || state_ == NOT_INITIALIZED)
+    return;  // Start() will re-fetch the MDP list later.
+
+  DCHECK((state_ == RUNNING && !dump_providers_.empty()) ||
+         (state_ == ENABLED && dump_providers_.empty()));
+
+  dump_providers_.clear();
+
+  // This is really MemoryDumpManager::GetDumpProvidersForPolling, % testing.
+  get_dump_providers_function_.Run(&dump_providers_);
+
+  if (state_ == ENABLED && !dump_providers_.empty()) {
+    // It's now time to start polling for realz.
+    state_ = RUNNING;
+    task_runner_->PostTask(FROM_HERE,
+                           Bind(&MemoryPeakDetector::PollMemoryAndDetectPeak,
+                                Unretained(this), ++generation_));
+  } else if (state_ == RUNNING && dump_providers_.empty()) {
+    // Will cause the next PollMemoryAndDetectPeak() task to early return.
+    state_ = ENABLED;
+    ++generation_;
+  }
+}
+
+void MemoryPeakDetector::PollMemoryAndDetectPeak(uint32_t expected_generation) {
+  if (state_ != RUNNING || expected_generation != generation_)
+    return;
+
+  // We should never end up in a situation where state_ == RUNNING but all dump
+  // providers are gone.
+  DCHECK(!dump_providers_.empty());
+
+  poll_tasks_count_for_testing_++;
+  uint64_t memory_total = 0;
+  for (const scoped_refptr<MemoryDumpProviderInfo>& mdp_info :
+       dump_providers_) {
+    DCHECK(mdp_info->options.is_fast_polling_supported);
+    uint64_t value = 0;
+    mdp_info->dump_provider->PollFastMemoryTotal(&value);
+    memory_total += value;
+  }
+  ignore_result(memory_total);  // TODO(primiano): temporary until next CL.
+
+  // TODO(primiano): Move actual peak detection logic from the
+  // MemoryDumpScheduler in next CLs.
+
+  SequencedTaskRunnerHandle::Get()->PostDelayedTask(
+      FROM_HERE,
+      Bind(&MemoryPeakDetector::PollMemoryAndDetectPeak, Unretained(this),
+           expected_generation),
+      TimeDelta::FromMilliseconds(polling_interval_ms_));
+}
+
+}  // namespace trace_event
+}  // namespace base