dom/base/nsWindowMemoryReporter.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef nsWindowMemoryReporter_h__
   8 #define nsWindowMemoryReporter_h__
   9
  10 #include "nsIMemoryReporter.h"
  11 #include "nsIObserver.h"
  12 #include "nsITimer.h"
  13 #include "nsDataHashtable.h"
  14 #include "nsWeakReference.h"
  15 #include "nsAutoPtr.h"
  16 #include "mozilla/Attributes.h"
  17 #include "mozilla/Assertions.h"
  18 #include "mozilla/MemoryReporting.h"
  19 #include "mozilla/PodOperations.h"
  20 #include "mozilla/TimeStamp.h"
  21 #include "nsArenaMemoryStats.h"
  22
  23 class nsWindowSizes {
  24 #define FOR_EACH_SIZE(macro) \
  25   macro(DOM,   mDOMElementNodesSize) \
  26   macro(DOM,   mDOMTextNodesSize) \
  27   macro(DOM,   mDOMCDATANodesSize) \
  28   macro(DOM,   mDOMCommentNodesSize) \
  29   macro(DOM,   mDOMEventTargetsSize) \
  30   macro(DOM,   mDOMOtherSize) \
  31   macro(Style, mStyleSheetsSize) \
  32   macro(Other, mLayoutPresShellSize) \
  33   macro(Style, mLayoutStyleSetsSize) \
  34   macro(Other, mLayoutTextRunsSize) \
  35   macro(Other, mLayoutPresContextSize) \
  36   macro(Other, mPropertyTablesSize) \
  37
  38 public:
  39   explicit nsWindowSizes(mozilla::MallocSizeOf aMallocSizeOf)
  40     :
  41       #define ZERO_SIZE(kind, mSize)  mSize(0),
  42       FOR_EACH_SIZE(ZERO_SIZE)
  43       #undef ZERO_SIZE
  44       mDOMEventTargetsCount(0),
  45       mDOMEventListenersCount(0),
  46       mArenaStats(),
  47       mMallocSizeOf(aMallocSizeOf)
  48   {}
  49
  50   void addToTabSizes(nsTabSizes *sizes) const {
  51     #define ADD_TO_TAB_SIZES(kind, mSize) sizes->add(nsTabSizes::kind, mSize);
  52     FOR_EACH_SIZE(ADD_TO_TAB_SIZES)
  53     #undef ADD_TO_TAB_SIZES
  54     mArenaStats.addToTabSizes(sizes);
  55   }
  56
  57   size_t getTotalSize() const
  58   {
  59     size_t total = 0;
  60     #define ADD_TO_TOTAL_SIZE(kind, mSize) total += mSize;
  61     FOR_EACH_SIZE(ADD_TO_TOTAL_SIZE)
  62     #undef ADD_TO_TOTAL_SIZE
  63     total += mArenaStats.getTotalSize();
  64     return total;
  65   }
  66
  67   #define DECL_SIZE(kind, mSize) size_t mSize;
  68   FOR_EACH_SIZE(DECL_SIZE);
  69   #undef DECL_SIZE
  70
  71   uint32_t mDOMEventTargetsCount;
  72   uint32_t mDOMEventListenersCount;
  73
  74   nsArenaMemoryStats mArenaStats;
  75   mozilla::MallocSizeOf mMallocSizeOf;
  76
  77 #undef FOR_EACH_SIZE
  78 };
  79
  80 /**
  81  * nsWindowMemoryReporter is responsible for the 'explicit/window-objects'
  82  * memory reporter.
  83  *
  84  * We classify DOM window objects into one of three categories:
  85  *
  86  *   - "active" windows, which are displayed in a tab (as the top-level window
  87  *     or an iframe),
  88  *
  89  *   - "cached" windows, which are in the fastback cache (aka the bfcache), and
  90  *
  91  *   - "detached" windows, which have a null docshell.  A window becomes
  92  *     detached when its <iframe> or tab containing the window is destroyed --
  93  *     i.e., when the window is no longer active or cached.
  94  *
  95  * Additionally, we classify a subset of detached windows as "ghost" windows.
  96  * Although ghost windows can happen legitimately (a page can hold a reference
  97  * to a cross-domain window and then close its container), the presence of
  98  * ghost windows is often indicative of a memory leak.
  99  *
 100  * A window is a ghost if it meets the following three criteria:
 101  *
 102  *   1) The window is detached.
 103  *
 104  *   2) There exist no non-detached windows with the same base domain as
 105  *      the window's principal.  (For example, the base domain of
 106  *      "wiki.mozilla.co.uk" is "mozilla.co.uk".)  This criterion makes us less
 107  *      likely to flag a legitimately held-alive detached window as a ghost.
 108  *
 109  *   3) The window has met criteria (1) and (2) above for at least
 110  *      memory.ghost_window_timeout_seconds.  This criterion is in place so we
 111  *      don't immediately declare a window a ghost before the GC/CC has had a
 112  *      chance to run.
 113  *
 114  * nsWindowMemoryReporter observes window detachment and uses mDetachedWindows
 115  * to remember when a window first met criteria (1) and (2).  When we generate
 116  * a memory report, we use this accounting to determine which windows are
 117  * ghosts.
 118  *
 119  *
 120  * We use the following memory reporter path for active and cached windows:
 121  *
 122  *   explicit/window-objects/top(<top-outer-uri>, id=<top-outer-id>)/<category>/window(<window-uri>)/...
 123  *
 124  * For detached and ghost windows, we use
 125  *
 126  *   explicit/window-objects/top(none)/<category>/window(<window-uri>)/...
 127  *
 128  * Where
 129  *
 130  * - <category> is "active", "cached", "detached", or "ghost", as described
 131  *   above.
 132  *
 133  * - <top-outer-id> is the window id of the top outer window (i.e. the tab, or
 134  *   the top level chrome window).  Exposing this ensures that each tab gets
 135  *   its own sub-tree, even if multiple tabs are showing the same URI.
 136  *
 137  * - <top-uri> is the URI of the top window.  Excepting special windows (such
 138  *   as browser.xul or hiddenWindow.html) it's what the address bar shows for
 139  *   the tab.
 140  *
 141  */
 142 class nsWindowMemoryReporter MOZ_FINAL : public nsIMemoryReporter,
 143                                          public nsIObserver,
 144                                          public nsSupportsWeakReference
 145 {
 146 public:
 147   NS_DECL_ISUPPORTS
 148   NS_DECL_NSIMEMORYREPORTER
 149   NS_DECL_NSIOBSERVER
 150
 151   static void Init();
 152
 153 #ifdef DEBUG
 154   /**
 155    * Unlink all known ghost windows, to enable investigating what caused them
 156    * to become ghost windows in the first place.
 157    */
 158   static void UnlinkGhostWindows();
 159 #endif
 160
 161 private:
 162   ~nsWindowMemoryReporter();
 163
 164   /**
 165    * nsGhostWindowReporter generates the "ghost-windows" report, which counts
 166    * the number of ghost windows present.
 167    */
 168   class GhostWindowsReporter MOZ_FINAL : public nsIMemoryReporter
 169   {
 170     ~GhostWindowsReporter() {}
 171   public:
 172     NS_DECL_ISUPPORTS
 173
 174     static int64_t DistinguishedAmount();
 175
 176     NS_IMETHOD
 177     CollectReports(nsIHandleReportCallback* aHandleReport, nsISupports* aData,
 178                    bool aAnonymize)
 179     {
 180       return MOZ_COLLECT_REPORT(
 181         "ghost-windows", KIND_OTHER, UNITS_COUNT, DistinguishedAmount(),
 182 "The number of ghost windows present (the number of nodes underneath "
 183 "explicit/window-objects/top(none)/ghost, modulo race conditions).  A ghost "
 184 "window is not shown in any tab, does not share a domain with any non-detached "
 185 "windows, and has met these criteria for at least "
 186 "memory.ghost_window_timeout_seconds, or has survived a round of "
 187 "about:memory's minimize memory usage button.\n\n"
 188 "Ghost windows can happen legitimately, but they are often indicative of "
 189 "leaks in the browser or add-ons.");
 190     }
 191   };
 192
 193   // Protect ctor, use Init() instead.
 194   nsWindowMemoryReporter();
 195
 196   /**
 197    * Get the number of seconds for which a window must satisfy ghost criteria
 198    * (1) and (2) before we deem that it satisfies criterion (3).
 199    */
 200   uint32_t GetGhostTimeout();
 201
 202   void ObserveDOMWindowDetached(nsISupports* aWindow);
 203   void ObserveAfterMinimizeMemoryUsage();
 204
 205   /**
 206    * Iterate over all weak window pointers in mDetachedWindows and update our
 207    * accounting of which windows meet ghost criterion (2).
 208    *
 209    * This method also cleans up mDetachedWindows, removing entries for windows
 210    * which have been destroyed or are no longer detached.
 211    *
 212    * If aOutGhostIDs is non-null, we populate it with the Window IDs of the
 213    * ghost windows.
 214    *
 215    * This is called asynchronously after we observe a DOM window being detached
 216    * from its docshell, and also right before we generate a memory report.
 217    */
 218   void CheckForGhostWindows(nsTHashtable<nsUint64HashKey> *aOutGhostIDs = nullptr);
 219
 220   /**
 221    * Eventually do a check for ghost windows, if we haven't done one recently
 222    * and we aren't already planning to do one soon.
 223    */
 224   void AsyncCheckForGhostWindows();
 225
 226   /**
 227    * Kill the check timer, if it exists.
 228    */
 229   void KillCheckTimer();
 230
 231   static void CheckTimerFired(nsITimer* aTimer, void* aClosure);
 232
 233   /**
 234    * Maps a weak reference to a detached window (nsIWeakReference) to the time
 235    * when we observed that the window met ghost criterion (2) above.
 236    *
 237    * If the window has not yet met criterion (2) it maps to the null timestamp.
 238    *
 239    * (Although windows are not added to this table until they're detached, it's
 240    * possible for a detached window to become non-detached, and we won't
 241    * remove it from the table until CheckForGhostWindows runs.)
 242    */
 243   nsDataHashtable<nsISupportsHashKey, mozilla::TimeStamp> mDetachedWindows;
 244
 245   /**
 246    * Track the last time we ran CheckForGhostWindows(), to avoid running it
 247    * too often after a DOM window is detached.
 248    */
 249   mozilla::TimeStamp mLastCheckForGhostWindows;
 250
 251   nsCOMPtr<nsITimer> mCheckTimer;
 252
 253   bool mCycleCollectorIsRunning;
 254
 255   bool mCheckTimerWaitingForCCEnd;
 256 };
 257
 258 #endif // nsWindowMemoryReporter_h__
 259