Trace-based benchmarking via a mojo app.

apps/benchmark/benchmark_app.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 <memory>
+#include <set>
+#include <string>
+#include <vector>
+
+#include "apps/benchmark/args.h"
+#include "apps/benchmark/event.h"
+#include "apps/benchmark/measurements.h"
+#include "apps/benchmark/trace_collector_client.h"
+#include "base/bind.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/strings/string_util.h"
+#include "base/time/time.h"
+#include "base/trace_event/trace_event.h"
+#include "mojo/application/application_runner_chromium.h"
+#include "mojo/public/c/system/main.h"
+#include "mojo/public/cpp/application/application_connection.h"
+#include "mojo/public/cpp/application/application_delegate.h"
+#include "mojo/public/cpp/application/application_impl.h"
+#include "mojo/services/tracing/public/interfaces/tracing.mojom.h"
+
+namespace benchmark {
+namespace {
+
+class BenchmarkApp : public mojo::ApplicationDelegate,
+                     public TraceCollectorClient::Receiver {
+ public:
+  BenchmarkApp() {}
+  ~BenchmarkApp() override {}
+
+  // mojo:ApplicationDelegate:
+  void Initialize(mojo::ApplicationImpl* app) override {
+    // Parse command-line arguments.
+    if (!GetArgs(app->args(), &args_)) {
+      mojo::ApplicationImpl::Terminate();

[jamesr, 2015/08/27 21:12:38]

maybe let the user know that the arguments didn't parse cleanly?

[ppi, 2015/08/28 12:15:11]

Done.

+      return;
+    }
+
+    // Calculate a list of trace categories we want to collect: a union of all
+    // categories targeted in measurements.
+    std::set<std::string> category_set;
+    for (const Measurement& measurement : args_.measurements) {
+      category_set.insert(measurement.target_event.category);
+    }
+    std::vector<std::string> unique_categories(category_set.begin(),
+                                               category_set.end());
+    std::string categories_str = JoinString(unique_categories, ',');

[jamesr, 2015/08/27 21:12:38]

hmm, this uses base::'s string utilities (which seems fine IMO) so why doesn't
the rest?

[ppi, 2015/08/28 12:15:11]

Done.

+
+    // Connect to trace collector, which will fetch the trace events produced by
+    // the app being benchmarked.
+    tracing::TraceCollectorPtr trace_collector;
+    app->ConnectToService("mojo:tracing", &trace_collector);
+    trace_collector_client_.reset(
+        new TraceCollectorClient(this, trace_collector.Pass()));
+    trace_collector_client_->Start(categories_str);
+
+    // Record the time origin for measurements just before connecting to the app
+    // being benchmarked.
+    time_origin_ = base::TimeTicks::FromInternalValue(MojoGetTimeTicksNow());
+    traced_app_connection_ = app->ConnectToApplication(args_.app);
+
+    // Post task to stop tracing when the time is up.
+    base::MessageLoop::current()->PostDelayedTask(
+        FROM_HERE,
+        base::Bind(&BenchmarkApp::StopTracing, base::Unretained(this)),
+        args_.duration);
+  }
+
+  void StopTracing() {
+    // Request the trace collector to send back the data. When the data is ready
+    // we will be called at OnTraceCollected().
+    trace_collector_client_->Stop();
+  }
+
+  // TraceCollectorClient::Receiver:
+  void OnTraceCollected(std::string trace_data) override {
+    // Parse trace events.
+    std::vector<Event> events;
+    if (!GetEvents(trace_data, &events)) {
+      LOG(ERROR) << "Failed to parse the trace data";
+      mojo::ApplicationImpl::Terminate();
+      return;
+    }
+
+    // Calculate and print the results.
+    bool succeeded = true;
+    Measurements measurements(events, time_origin_);
+    for (const Measurement& measurement : args_.measurements) {
+      double result = measurements.Measure(measurement);
+      if (result >= 0.0) {
+        printf("measurement: %s %lf\n", measurement.spec.c_str(), result);
+      } else {
+        succeeded = false;
+        printf("measurement: %s FAILED\n", measurement.spec.c_str());
+      }
+    }
+
+    // Scripts that run benchmarks can pick this up as a signal that the run
+    // succeeded, as shell exit code is 0 even if an app exits early due to an
+    // error.
+    if (succeeded) {
+      printf("benchmark succeeded\n");
+    } else {
+      printf("some measurements failed\n");
+    }
+    mojo::ApplicationImpl::Terminate();
+  }
+
+ private:
+  Args args_;
+  mojo::ApplicationConnection* traced_app_connection_;
+  scoped_ptr<TraceCollectorClient> trace_collector_client_;
+  base::TimeTicks time_origin_;
+
+  DISALLOW_COPY_AND_ASSIGN(BenchmarkApp);
+};
+}  // namespace
+}  // namespace benchmark
+
+MojoResult MojoMain(MojoHandle application_request) {
+  mojo::ApplicationRunnerChromium runner(new benchmark::BenchmarkApp);
+  auto ret = runner.Run(application_request);
+  fflush(nullptr);
+  return ret;
+}