gecko-dev/xpcom/build/perfprobe.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/**
 * A mechanism for interacting with operating system-provided
 * debugging/profiling tools such as Microsoft EWT/Windows Performance Toolkit.
 */

#ifndef mozilla_perfprobe_h
#define mozilla_perfprobe_h

#if !defined(XP_WIN)
#  error "For the moment, perfprobe.h is defined only for Windows platforms"
#endif

#include "nsError.h"
#include "nsString.h"
#include "mozilla/Logging.h"
#include "nsTArray.h"
#include <windows.h>
#undef GetStartupInfo  // Prevent Windows from polluting global namespace
#include <wmistr.h>
#include <evntrace.h>

namespace mozilla {
namespace probes {

class ProbeManager;

/**
 * A data structure supporting a trigger operation that can be used to
 * send information to the operating system.
 */

class Probe {
 public:
  NS_INLINE_DECL_REFCOUNTING(Probe)

  /**
   * Trigger the event.
   *
   * Note: Can be called from any thread.
   */
  nsresult Trigger();

 protected:
  ~Probe(){};

  Probe(const nsCID& aGUID, const nsACString& aName, ProbeManager* aManager);
  friend class ProbeManager;

 protected:
  /**
   * The system GUID associated to this probe. See the documentation
   * of |ProbeManager::Make| for more details.
   */
  const GUID mGUID;

  /**
   * The name of this probe. See the documentation
   * of |ProbeManager::Make| for more details.
   */
  const nsCString mName;

  /**
   * The ProbeManager managing this probe.
   *
   * Note: This is a weak reference to avoid a useless cycle.
   */
  class ProbeManager* mManager;
};

/**
 * A manager for a group of probes.
 *
 * You can have several managers in one application, provided that they all
 * have distinct IDs and names. However, having more than 2 is considered a bad
 * practice.
 */
class ProbeManager {
 public:
  NS_INLINE_DECL_REFCOUNTING(ProbeManager)

  /**
   * Create a new probe manager.
   *
   * This constructor should be called from the main thread.
   *
   * @param aApplicationUID The unique ID of the probe. Under Windows, this
   * unique ID must have been previously registered using an external tool.
   * See MyCategory on http://msdn.microsoft.com/en-us/library/aa364100.aspx
   * @param aApplicationName A name for the probe. Currently used only for
   * logging purposes. In the future, may be attached to the data sent to the
   * operating system.
   *
   * Note: If two ProbeManagers are constructed with the same uid and/or name,
   * behavior is unspecified.
   */
  ProbeManager(const nsCID& aApplicationUID,
               const nsACString& aApplicationName);

  /**
   * Acquire a probe.
   *
   * Note: Only probes acquired before the call to SetReady are taken into
   * account
   * Note: Can be called only from the main thread.
   *
   * @param aEventUID The unique ID of the probe. Under Windows, this unique
   * ID must have been previously registered using an external tool.
   * See MyCategory on http://msdn.microsoft.com/en-us/library/aa364100.aspx
   * @param aEventName A name for the probe. Currently used only for logging
   * purposes. In the
   * future, may be attached to the data sent to the operating system.
   * @return Either |null| in case of error or a valid |Probe*|.
   *
   * Note: If this method is called twice with the same uid and/or name,
   * behavior is undefined.
   */
  already_AddRefed<Probe> GetProbe(const nsCID& aEventUID,
                                   const nsACString& aEventName);

  /**
   * Start/stop the measuring session.
   *
   * This method should be called from the main thread.
   *
   * Note that starting an already started probe manager has no effect,
   * nor does stopping an already stopped probe manager.
   */
  nsresult StartSession();
  nsresult StopSession();

  /**
   * @return true If measures are currently on, i.e. if triggering probes is any
   * is useful. You do not have to check this before triggering a probe, unless
   * this can avoid complex computations.
   */
  bool IsActive();

 protected:
  ~ProbeManager();

  nsresult StartSession(nsTArray<RefPtr<Probe>>& aProbes);
  nsresult Init(const nsCID& aApplicationUID,
                const nsACString& aApplicationName);

 protected:
  /**
   * `true` if a session is in activity, `false` otherwise.
   */
  bool mIsActive;

  /**
   * The UID of this manager.
   * See documentation above for registration steps that you
   * may have to take.
   */
  nsCID mApplicationUID;

  /**
   * The name of the application.
   */
  nsCString mApplicationName;

  /**
   * All the probes that have been created for this manager.
   */
  nsTArray<RefPtr<Probe>> mAllProbes;

  /**
   * Handle used for triggering events
   */
  TRACEHANDLE mSessionHandle;

  /**
   * Handle used for registration/unregistration
   */
  TRACEHANDLE mRegistrationHandle;

  /**
   * `true` if initialization has been performed, `false` until then.
   */
  bool mInitialized;

  friend class Probe;  // Needs to access |mSessionHandle|
  friend ULONG WINAPI ControlCallback(WMIDPREQUESTCODE aRequestCode,
                                      PVOID aContext, ULONG* aReserved,
                                      PVOID aBuffer);  // Sets |mSessionHandle|
};

}  // namespace probes
}  // namespace mozilla

#endif  // mozilla_perfprobe_h