metrics/base: log whether drives have seek penalties.

chrome/browser/metrics/drive_metrics_provider.h

+// 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.
+
+#ifndef CHROME_BROWSER_METRICS_DRIVE_METRICS_PROVIDER_H_
+#define CHROME_BROWSER_METRICS_DRIVE_METRICS_PROVIDER_H_
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/threading/thread_checker.h"
+#include "components/metrics/metrics_provider.h"
+#include "components/metrics/proto/system_profile.pb.h"
+
+// Provides metrics about the local drives on a user's computer. Currently only
+// checks to see if they incur a seek-time penalty (e.g. if they're SSDs).
+//
+// Defers gathering metrics until after "rush hour" (startup) so as to not bog
+// down the FILE thread.
+class DriveMetricsProvider : public metrics::MetricsProvider {
+ public:
+  DriveMetricsProvider();
+  ~DriveMetricsProvider() override;
+
+  // metrics::MetricsDataProvider:
+  void ProvideSystemProfileMetrics(
+      metrics::SystemProfileProto* system_profile_proto) override;
+
+ private:
+  // A response to querying a drive as to whether it incurs a seek penalty.
+  // |has_seek_penalty| is set if |success| is true.
+  struct SeekPenaltyResponse {
+    SeekPenaltyResponse();
+    bool success;
+    bool has_seek_penalty;
+  };
+
+  struct DriveMetrics {
+    SeekPenaltyResponse app_drive;
+    SeekPenaltyResponse user_data_drive;
+  };
+
+  // Gather metrics about various drives on the FILE thread.
+  DriveMetrics GetDriveMetrics();
+
+  // Tries to determine whether there is a penalty for seeking on the drive that
+  // hosts |path_service_key| (for example: the drive that holds "Local State").
+  void QuerySeekPenalty(int path_service_key, SeekPenaltyResponse* response);
+
+  // Called when metrics are done being gathered from the FILE thread.
+  void GotDriveMetrics(const DriveMetrics& metrics);
+
+  // Fills |drive| with information from successful |response|s.
+  void FillDriveMetrics(
+      const SeekPenaltyResponse& response,
+      metrics::SystemProfileProto::Hardware::Drive* drive);
+
+  // False until |GotDriveMetrics| is called.
+  bool got_metrics_;
+
+  // Information gathered about various important drives.
+  DriveMetrics metrics_;
+
+  base::ThreadChecker thread_checker_;
+  base::WeakPtrFactory<DriveMetricsProvider> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(DriveMetricsProvider);
+};
+
+#endif  // CHROME_BROWSER_METRICS_DRIVE_METRICS_PROVIDER_H_