Metrics provider for statistical stack profiler

chrome/browser/metrics/call_stack_profile_metrics_provider.cc

+// Copyright 2015 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 "call_stack_profile_metrics_provider.h"
+
+#include "base/md5.h"
+#include "base/profiler/stack_sampling_profiler.h"
+#include "components/metrics/proto/chrome_user_metrics_extension.pb.h"
+
+using base::StackSamplingProfiler;
+using metrics::CallStackProfile;
+using metrics::CallStackEntry;

[Ilya Sherman, 2015/03/10 01:44:46]

nit: Please alphabetize

[Mike Wittman, 2015/03/16 23:55:14]

Done.

+using metrics::ChromeUserMetricsExtension;
+using metrics::ModuleIdentifier;
+using metrics::SampledProfile;
+
+namespace {

[Ilya Sherman, 2015/03/10 01:44:46]

nit: Please include a blank line after this one.

[Mike Wittman, 2015/03/16 23:55:15]

Done.

+// The protobuf expects the MD5 checksum prefix of the module name.
+uint64 HashModuleFilename(const base::FilePath& filename) {
+  const base::FilePath::StringType basename = filename.BaseName().value();
+  base::MD5Digest md5;
+  base::MD5Sum(&basename[0], basename.size() * sizeof(base::FilePath::CharType),
+               &md5);
+  return *reinterpret_cast<uint64*>(&md5.a[0]);
+}
+
+void CopySampleToProto(const StackSamplingProfiler::Sample& sample,
+                       CallStackProfile::Sample* proto_sample) {

[Ilya Sherman, 2015/03/10 01:44:46]

nit: Please document all functions, including local ones.

[Mike Wittman, 2015/03/16 23:55:15]

Done.

+  for (const StackSamplingProfiler::Frame& frame : sample) {
+    CallStackEntry* call_stack_entry = proto_sample->add_entries();
+    call_stack_entry->set_address(frame.ip_offset);
+    call_stack_entry->set_module_id_index(frame.module_index);
+  }
+}
+
+void CopyProfileToProto(
+    const StackSamplingProfiler::Profile& profile,
+    metrics::CallStackProfile* proto_profile) {
+  if (profile.samples.empty())
+    return;
+
+  CallStackProfile::Sample* current_sample_proto = nullptr;
+  for (auto it = profile.samples.begin(); it != profile.samples.end(); ++it) {
+    if (!current_sample_proto || *it != *(it - 1)) {

[Ilya Sherman, 2015/03/10 01:44:46]

Hmm, this seems like a surprising design.  Why doesn't the Profile use a map
representation to count the number of samples for each function?

[Mike Wittman, 2015/03/16 23:55:15]

After further discussion, we want to support two different use cases here:
profiles where the sequence of sample stacks is important and should be
preserved, and profiles where the sample stacks are essentially independent and
sequence is not important.

I've added a preserve_sample_ordering variable to the input to distinguish
between the two, and updated the code to handle the unordered case with a map.

+      current_sample_proto = proto_profile->add_samples();
+      CopySampleToProto(profile.samples.front(), current_sample_proto);
+      current_sample_proto->set_count(1);
+    } else {
+      current_sample_proto->set_count(current_sample_proto->count() + 1);
+    }
+  }
+
+  for (const StackSamplingProfiler::Module& module : profile.modules) {
+    ModuleIdentifier* module_id = proto_profile->add_module_ids();
+    module_id->set_build_id(module.id);
+    module_id->set_name_md5_prefix(HashModuleFilename(module.filename));
+  }
+
+  proto_profile->set_profile_duration_ms(
+      profile.profile_duration.InMilliseconds());
+  proto_profile->set_sampling_period_ms(
+      profile.sampling_period.InMilliseconds());
+}
+}  // namespace
+
+CallStackProfileMetricsProvider::CallStackProfileMetricsProvider() {}
+
+CallStackProfileMetricsProvider::~CallStackProfileMetricsProvider() {}
+
+void CallStackProfileMetricsProvider::ProvideGeneralMetrics(
+    metrics::ChromeUserMetricsExtension* uma_proto) {
+  std::vector<StackSamplingProfiler::Profile> profiles;
+  StackSamplingProfiler::GetPendingProfiles(&profiles);
+
+  for (StackSamplingProfiler::Profile profile : profiles) {
+    CallStackProfile* call_stack_profile =
+        uma_proto->add_sampled_profile()->mutable_call_stack_profile();
+    CopyProfileToProto(profile, call_stack_profile);
+  }
+}