/* -*- 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/. */
/** * nsWindowMemoryReporter is responsible for the 'explicit/window-objects' * memory reporter. * * We classify DOM window objects into one of three categories: * * - "active" windows, which are displayed in a tab (as the top-level window * or an iframe), * * - "cached" windows, which are in the fastback cache (aka the bfcache), and * * - "detached" windows, which have a null docshell. A window becomes * detached when its <iframe> or tab containing the window is destroyed -- * i.e., when the window is no longer active or cached. * * Additionally, we classify a subset of detached windows as "ghost" windows. * Although ghost windows can happen legitimately (a page can hold a reference * to a cross-domain window and then close its container), the presence of * ghost windows is often indicative of a memory leak. * * A window is a ghost if it meets the following three criteria: * * 1) The window is detached. * * 2) There exist no non-detached windows with the same base domain as * the window's principal. (For example, the base domain of * "wiki.mozilla.co.uk" is "mozilla.co.uk".) This criterion makes us less * likely to flag a legitimately held-alive detached window as a ghost. * * 3) The window has met criteria (1) and (2) above for at least * memory.ghost_window_timeout_seconds. This criterion is in place so we * don't immediately declare a window a ghost before the GC/CC has had a * chance to run. * * nsWindowMemoryReporter observes window detachment and uses mDetachedWindows * to remember when a window first met criteria (1) and (2). When we generate * a memory report, we use this accounting to determine which windows are * ghosts. * * * We use the following memory reporter path for active and cached windows: * * explicit/window-objects/top(<top-outer-uri>, id=<top-outer-id>)/ * <category>/window(<window-uri>)/... * * For detached and ghost windows, we use * * explicit/window-objects/top(none)/<category>/window(<window-uri>)/... * * Where * * - <category> is "active", "cached", "detached", or "ghost", as described * above. * * - <top-outer-id> is the window id of the top outer window (i.e. the tab, or * the top level chrome window). Exposing this ensures that each tab gets * its own sub-tree, even if multiple tabs are showing the same URI. * * - <top-uri> is the URI of the top window. Excepting special windows (such * as browser.xhtml or hiddenWindowMac.xhtml) it's what the address bar shows * for the tab. *
*/ class nsWindowMemoryReporter final : public nsIMemoryReporter, public nsIObserver, public nsSupportsWeakReference { public:
NS_DECL_ISUPPORTS
NS_DECL_NSIMEMORYREPORTER
NS_DECL_NSIOBSERVER
staticvoid Init();
#ifdef DEBUG /** * Unlink all known ghost windows, to enable investigating what caused them * to become ghost windows in the first place.
*/ staticvoid UnlinkGhostWindows(); #endif
// Protect ctor, use Init() instead.
nsWindowMemoryReporter();
/** * Get the number of seconds for which a window must satisfy ghost criteria * (1) and (2) before we deem that it satisfies criterion (3).
*/
uint32_t GetGhostTimeout();
void ObserveAfterMinimizeMemoryUsage();
/** * Iterate over all weak window pointers in mDetachedWindows and update our * accounting of which windows meet ghost criterion (2). * * This method also cleans up mDetachedWindows, removing entries for windows * which have been destroyed or are no longer detached. * * If aOutGhostIDs is non-null, we populate it with the Window IDs of the * ghost windows. * * This is called asynchronously after we observe a DOM window being detached * from its docshell, and also right before we generate a memory report.
*/ void CheckForGhostWindows(nsTHashSet<uint64_t>* aOutGhostIDs = nullptr);
/** * Eventually do a check for ghost windows, if we haven't done one recently * and we aren't already planning to do one soon.
*/ void AsyncCheckForGhostWindows();
/** * Kill the check timer, if it exists.
*/ void KillCheckTimer();
/** * Maps a weak reference to a detached window (nsIWeakReference) to the time * when we observed that the window met ghost criterion (2) above. * * If the window has not yet met criterion (2) it maps to the null timestamp. * * (Although windows are not added to this table until they're detached, it's * possible for a detached window to become non-detached, and we won't * remove it from the table until CheckForGhostWindows runs.)
*/
nsTHashMap<nsISupportsHashKey, mozilla::TimeStamp> mDetachedWindows;
/** * Track the last time we ran CheckForGhostWindows(), to avoid running it * too often after a DOM window is detached.
*/
mozilla::TimeStamp mLastCheckForGhostWindows;
nsCOMPtr<nsITimer> mCheckTimer;
bool mCycleCollectorIsRunning;
bool mCheckTimerWaitingForCCEnd;
int64_t mGhostWindowCount;
};
#endif// nsWindowMemoryReporter_h__
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