path: root/xpcom/base/nsMemoryReporterManager.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/. */

#ifndef nsMemoryReporterManager_h__
#define nsMemoryReporterManager_h__

#include "mozilla/Mutex.h"
#include "nsHashKeys.h"
#include "nsIMemoryReporter.h"
#include "nsITimer.h"
#include "nsServiceManagerUtils.h"
#include "nsTHashtable.h"

namespace mozilla {
namespace dom {
class ContentParent;
class MemoryReport;
} // namespace dom
} // namespace mozilla

class nsITimer;

class nsMemoryReporterManager final : public nsIMemoryReporterManager
{
  virtual ~nsMemoryReporterManager();

public:
  NS_DECL_THREADSAFE_ISUPPORTS
  NS_DECL_NSIMEMORYREPORTERMANAGER

  nsMemoryReporterManager();

  // Gets the memory reporter manager service.
  static nsMemoryReporterManager* GetOrCreate()
  {
    nsCOMPtr<nsIMemoryReporterManager> imgr =
      do_GetService("@mozilla.org/memory-reporter-manager;1");
    return static_cast<nsMemoryReporterManager*>(imgr.get());
  }

  typedef nsDataHashtable<nsRefPtrHashKey<nsIMemoryReporter>, bool> StrongReportersTable;
  typedef nsDataHashtable<nsPtrHashKey<nsIMemoryReporter>, bool> WeakReportersTable;

  // Inter-process memory reporting proceeds as follows.
  //
  // - GetReports() (declared within NS_DECL_NSIMEMORYREPORTERMANAGER)
  //   synchronously gets memory reports for the current process, sets up some
  //   state (mPendingProcessesState) for when child processes report back --
  //   including a timer -- and starts telling child processes to get memory
  //   reports.  Control then returns to the main event loop.
  //
  //   The number of concurrent child process reports is limited by the pref
  //   "memory.report_concurrency" in order to prevent the memory overhead of
  //   memory reporting from causing problems, especially on B2G when swapping
  //   to compressed RAM; see bug 1154053.
  //
  // - HandleChildReport() is called (asynchronously) once per child process
  //   reporter callback.
  //
  // - EndProcessReport() is called (asynchronously) once per process that
  //   finishes reporting back, including the parent.  If all processes do so
  //   before time-out, the timer is cancelled.  If there are child processes
  //   whose requests have not yet been sent, they will be started until the
  //   concurrency limit is (again) reached.
  //
  // - TimeoutCallback() is called (asynchronously) if all the child processes
  //   don't respond within the time threshold.
  //
  // - FinishReporting() finishes things off.  It is *always* called -- either
  //   from EndChildReport() (if all child processes have reported back) or
  //   from TimeoutCallback() (if time-out occurs).
  //
  // All operations occur on the main thread.
  //
  // The above sequence of steps is a "request".  A partially-completed request
  // is described as "in flight".
  //
  // Each request has a "generation", a unique number that identifies it.  This
  // is used to ensure that each reports from a child process corresponds to
  // the appropriate request from the parent process.  (It's easier to
  // implement a generation system than to implement a child report request
  // cancellation mechanism.)
  //
  // Failures are mostly ignored, because it's (a) typically the most sensible
  // thing to do, and (b) often hard to do anything else.  The following are
  // the failure cases of note.
  //
  // - If a request is made while the previous request is in flight, the new
  //   request is ignored, as per getReports()'s specification.  No error is
  //   reported, because the previous request will complete soon enough.
  //
  // - If one or more child processes fail to respond within the time limit,
  //   things will proceed as if they don't exist.  No error is reported,
  //   because partial information is better than nothing.
  //
  // - If a child process reports after the time-out occurs, it is ignored.
  //   (Generation checking will ensure it is ignored even if a subsequent
  //   request is in flight;  this is the main use of generations.)  No error
  //   is reported, because there's nothing sensible to be done about it at
  //   this late stage.
  //
  // - If the time-out occurs after a child process has sent some reports but
  //   before it has signaled completion (see bug 1151597), then what it
  //   successfully sent will be included, with no explicit indication that it
  //   is incomplete.
  //
  // Now, what what happens if a child process is created/destroyed in the
  // middle of a request?  Well, PendingProcessesState is initialized with an array
  // of child process actors as of when the report started.  So...
  //
  // - If a process is created after reporting starts, it won't be sent a
  //   request for reports.  So the reported data will reflect how things were
  //   when the request began.
  //
  // - If a process is destroyed before it starts reporting back, the reported
  //   data will reflect how things are when the request ends.
  //
  // - If a process is destroyed after it starts reporting back but before it
  //   finishes, the reported data will contain a partial report for it.
  //
  // - If a process is destroyed after reporting back, but before all other
  //   child processes have reported back, it will be included in the reported
  //   data.  So the reported data will reflect how things were when the
  //   request began.
  //
  // The inconsistencies between these cases are unfortunate but difficult to
  // avoid.  It's enough of an edge case to not be worth doing more.
  //
  void HandleChildReport(uint32_t aGeneration,
                         const mozilla::dom::MemoryReport& aChildReport);
  void EndProcessReport(uint32_t aGeneration, bool aSuccess);

  // Functions that (a) implement distinguished amounts, and (b) are outside of
  // this module.
  struct AmountFns
  {
    mozilla::InfallibleAmountFn mJSMainRuntimeGCHeap;
    mozilla::InfallibleAmountFn mJSMainRuntimeTemporaryPeak;
    mozilla::InfallibleAmountFn mJSMainRuntimeCompartmentsSystem;
    mozilla::InfallibleAmountFn mJSMainRuntimeCompartmentsUser;

    mozilla::InfallibleAmountFn mImagesContentUsedUncompressed;

    mozilla::InfallibleAmountFn mStorageSQLite;

    mozilla::InfallibleAmountFn mLowMemoryEventsVirtual;
    mozilla::InfallibleAmountFn mLowMemoryEventsPhysical;

    mozilla::InfallibleAmountFn mGhostWindows;

    AmountFns()
    {
      mozilla::PodZero(this);
    }
  };
  AmountFns mAmountFns;

  // Convenience function to get RSS easily from other code.  This is useful
  // when debugging transient memory spikes with printf instrumentation.
  static int64_t ResidentFast();

  // Convenience function to get peak RSS easily from other code.
  static int64_t ResidentPeak();

  // Convenience function to get USS easily from other code.  This is useful
  // when debugging unshared memory pages for forked processes.
  static int64_t ResidentUnique();

  // Functions that measure per-tab memory consumption.
  struct SizeOfTabFns
  {
    mozilla::JSSizeOfTabFn    mJS;
    mozilla::NonJSSizeOfTabFn mNonJS;

    SizeOfTabFns()
    {
      mozilla::PodZero(this);
    }
  };
  SizeOfTabFns mSizeOfTabFns;

private:
  [[nodiscard]] nsresult
  RegisterReporterHelper(nsIMemoryReporter* aReporter,
                         bool aForce, bool aStrongRef, bool aIsAsync);

  [[nodiscard]] nsresult StartGettingReports();
  // No [[nodiscard]] here because ignoring the result is common and reasonable.
  nsresult FinishReporting();

  void DispatchReporter(nsIMemoryReporter* aReporter, bool aIsAsync,
                        nsIHandleReportCallback* aHandleReport,
                        nsISupports* aHandleReportData,
                        bool aAnonymize);

  static void TimeoutCallback(nsITimer* aTimer, void* aData);
  // Note: this timeout needs to be long enough to allow for the
  // possibility of DMD reports and/or running on a low-end phone.
  static const uint32_t kTimeoutLengthMS = 50000;

  mozilla::Mutex mMutex;
  bool mIsRegistrationBlocked;

  StrongReportersTable* mStrongReporters;
  WeakReportersTable* mWeakReporters;

  // These two are only used for testing purposes.
  StrongReportersTable* mSavedStrongReporters;
  WeakReportersTable* mSavedWeakReporters;

  uint32_t mNextGeneration;

  // Used to keep track of state of which processes are currently running and
  // waiting to run memory reports. Holds references to parameters needed when
  // requesting a memory report and finishing reporting.
  struct PendingProcessesState
  {
    uint32_t                             mGeneration;
    bool                                 mAnonymize;
    bool                                 mMinimize;
    nsCOMPtr<nsITimer>                   mTimer;
    nsTArray<RefPtr<mozilla::dom::ContentParent>> mChildrenPending;
    uint32_t                             mNumProcessesRunning;
    uint32_t                             mNumProcessesCompleted;
    uint32_t                             mConcurrencyLimit;
    nsCOMPtr<nsIHandleReportCallback>    mHandleReport;
    nsCOMPtr<nsISupports>                mHandleReportData;
    nsCOMPtr<nsIFinishReportingCallback> mFinishReporting;
    nsCOMPtr<nsISupports>                mFinishReportingData;
    nsString                             mDMDDumpIdent;

    PendingProcessesState(uint32_t aGeneration, bool aAnonymize, bool aMinimize,
                          uint32_t aConcurrencyLimit,
                          nsIHandleReportCallback* aHandleReport,
                          nsISupports* aHandleReportData,
                          nsIFinishReportingCallback* aFinishReporting,
                          nsISupports* aFinishReportingData,
                          const nsAString& aDMDDumpIdent);
  };

  // Used to keep track of the state of the asynchronously run memory
  // reporters. The callback and file handle used when all memory reporters
  // have finished are also stored here.
  struct PendingReportersState
  {
    // Number of memory reporters currently running.
    uint32_t mReportsPending;

    // Callback for when all memory reporters have completed.
    nsCOMPtr<nsIFinishReportingCallback> mFinishReporting;
    nsCOMPtr<nsISupports> mFinishReportingData;

    // File handle to write a DMD report to if requested.
    FILE* mDMDFile;

    PendingReportersState(nsIFinishReportingCallback* aFinishReporting,
                        nsISupports* aFinishReportingData,
                        FILE* aDMDFile)
      : mReportsPending(0)
      , mFinishReporting(aFinishReporting)
      , mFinishReportingData(aFinishReportingData)
      , mDMDFile(aDMDFile)
    {
    }
  };

  // When this is non-null, a request is in flight.  Note: We use manual
  // new/delete for this because its lifetime doesn't match block scope or
  // anything like that.
  PendingProcessesState* mPendingProcessesState;

  // This is reinitialized each time a call to GetReports is initiated.
  PendingReportersState* mPendingReportersState;

  PendingProcessesState* GetStateForGeneration(uint32_t aGeneration);
  [[nodiscard]] static bool
  StartChildReport(mozilla::dom::ContentParent* aChild,
                   const PendingProcessesState* aState);
};

#define NS_MEMORY_REPORTER_MANAGER_CID \
{ 0xfb97e4f5, 0x32dd, 0x497a, \
{ 0xba, 0xa2, 0x7d, 0x1e, 0x55, 0x7, 0x99, 0x10 } }

#endif // nsMemoryReporterManager_h__