Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 523 insertions, 0 deletions

diff --git a/browser/modules/TabUnloader.jsm b/browser/modules/TabUnloader.jsm
new file mode 100644
index 0000000000..1baf177df7
--- /dev/null
+++ b/browser/modules/TabUnloader.jsm
@@ -0,0 +1,523 @@
+/* -*- mode: js; indent-tabs-mode: nil; js-indent-level: 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/. */
+
+"use strict";
+
+/*
+ * TabUnloader is used to discard tabs when memory or resource constraints
+ * are reached. The discarded tabs are determined using a heuristic that
+ * accounts for when the tab was last used, how many resources the tab uses,
+ * and whether the tab is likely to affect the user if it is closed.
+ */
+var EXPORTED_SYMBOLS = ["TabUnloader"];
+
+const lazy = {};
+
+ChromeUtils.defineModuleGetter(
+  lazy,
+  "webrtcUI",
+  "resource:///modules/webrtcUI.jsm"
+);
+ChromeUtils.defineESModuleGetters(lazy, {
+  PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.sys.mjs",
+});
+
+// If there are only this many or fewer tabs open, just sort by weight, and close
+// the lowest tab. Otherwise, do a more intensive compuation that determines the
+// tabs to close based on memory and process use.
+const MIN_TABS_COUNT = 10;
+
+// Weight for non-discardable tabs.
+const NEVER_DISCARD = 100000;
+
+// Default minimum inactive duration.  Tabs that were accessed in the last
+// period of this duration are not unloaded.
+const kMinInactiveDurationInMs = Services.prefs.getIntPref(
+  "browser.tabs.min_inactive_duration_before_unload"
+);
+
+let criteriaTypes = [
+  ["isNonDiscardable", NEVER_DISCARD],
+  ["isLoading", 8],
+  ["usingPictureInPicture", NEVER_DISCARD],
+  ["playingMedia", NEVER_DISCARD],
+  ["usingWebRTC", NEVER_DISCARD],
+  ["isPinned", 2],
+  ["isPrivate", NEVER_DISCARD],
+];
+
+// Indicies into the criteriaTypes lists.
+let CRITERIA_METHOD = 0;
+let CRITERIA_WEIGHT = 1;
+
+/**
+ * This is an object that supplies methods that determine details about
+ * each tab. This default object is used if another one is not passed
+ * to the tab unloader functions. This allows tests to override the methods
+ * with tab specific data rather than creating test tabs.
+ */
+let DefaultTabUnloaderMethods = {
+  isNonDiscardable(tab, weight) {
+    if (tab.selected) {
+      return weight;
+    }
+
+    return !tab.linkedBrowser.isConnected ? -1 : 0;
+  },
+
+  isPinned(tab, weight) {
+    return tab.pinned ? weight : 0;
+  },
+
+  isLoading(tab, weight) {
+    return 0;
+  },
+
+  usingPictureInPicture(tab, weight) {
+    // This has higher weight even when paused.
+    return tab.pictureinpicture ? weight : 0;
+  },
+
+  playingMedia(tab, weight) {
+    return tab.soundPlaying ? weight : 0;
+  },
+
+  usingWebRTC(tab, weight) {
+    const browser = tab.linkedBrowser;
+    if (!browser) {
+      return 0;
+    }
+
+    // No need to iterate browser contexts for hasActivePeerConnection
+    // because hasActivePeerConnection is set only in the top window.
+    return lazy.webrtcUI.browserHasStreams(browser) ||
+      browser.browsingContext?.currentWindowGlobal?.hasActivePeerConnections()
+      ? weight
+      : 0;
+  },
+
+  isPrivate(tab, weight) {
+    return lazy.PrivateBrowsingUtils.isBrowserPrivate(tab.linkedBrowser)
+      ? weight
+      : 0;
+  },
+
+  getMinTabCount() {
+    return MIN_TABS_COUNT;
+  },
+
+  getNow() {
+    return Date.now();
+  },
+
+  *iterateTabs() {
+    for (let win of Services.wm.getEnumerator("navigator:browser")) {
+      for (let tab of win.gBrowser.tabs) {
+        yield { tab, gBrowser: win.gBrowser };
+      }
+    }
+  },
+
+  *iterateBrowsingContexts(bc) {
+    yield bc;
+    for (let childBC of bc.children) {
+      yield* this.iterateBrowsingContexts(childBC);
+    }
+  },
+
+  *iterateProcesses(tab) {
+    let bc = tab?.linkedBrowser?.browsingContext;
+    if (!bc) {
+      return;
+    }
+
+    const iter = this.iterateBrowsingContexts(bc);
+    for (let childBC of iter) {
+      if (childBC?.currentWindowGlobal) {
+        yield childBC.currentWindowGlobal.osPid;
+      }
+    }
+  },
+
+  /**
+   * Add the amount of memory used by each process to the process map.
+   *
+   * @param tabs array of tabs, used only by unit tests
+   * @param map of processes returned by getAllProcesses.
+   */
+  async calculateMemoryUsage(processMap) {
+    let parentProcessInfo = await ChromeUtils.requestProcInfo();
+    let childProcessInfoList = parentProcessInfo.children;
+    for (let childProcInfo of childProcessInfoList) {
+      let processInfo = processMap.get(childProcInfo.pid);
+      if (!processInfo) {
+        processInfo = { count: 0, topCount: 0, tabSet: new Set() };
+        processMap.set(childProcInfo.pid, processInfo);
+      }
+      processInfo.memory = childProcInfo.memory;
+    }
+  },
+};
+
+/**
+ * This module is responsible for detecting low-memory scenarios and unloading
+ * tabs in response to them.
+ */
+
+var TabUnloader = {
+  /**
+   * Initialize low-memory detection and tab auto-unloading.
+   */
+  init() {
+    const watcher = Cc["@mozilla.org/xpcom/memory-watcher;1"].getService(
+      Ci.nsIAvailableMemoryWatcherBase
+    );
+    watcher.registerTabUnloader(this);
+  },
+
+  isDiscardable(tab) {
+    if (!("weight" in tab)) {
+      return false;
+    }
+    return tab.weight < NEVER_DISCARD;
+  },
+
+  // This method is exposed on nsITabUnloader
+  async unloadTabAsync(minInactiveDuration = kMinInactiveDurationInMs) {
+    const watcher = Cc["@mozilla.org/xpcom/memory-watcher;1"].getService(
+      Ci.nsIAvailableMemoryWatcherBase
+    );
+
+    if (!Services.prefs.getBoolPref("browser.tabs.unloadOnLowMemory", true)) {
+      watcher.onUnloadAttemptCompleted(Cr.NS_ERROR_NOT_AVAILABLE);
+      return;
+    }
+
+    if (this._isUnloading) {
+      // Don't post multiple unloading requests.  The situation may be solved
+      // when the active unloading task is completed.
+      Services.console.logStringMessage("Unloading a tab is in progress.");
+      watcher.onUnloadAttemptCompleted(Cr.NS_ERROR_ABORT);
+      return;
+    }
+
+    this._isUnloading = true;
+    const isTabUnloaded = await this.unloadLeastRecentlyUsedTab(
+      minInactiveDuration
+    );
+    this._isUnloading = false;
+
+    watcher.onUnloadAttemptCompleted(
+      isTabUnloaded ? Cr.NS_OK : Cr.NS_ERROR_NOT_AVAILABLE
+    );
+  },
+
+  /**
+   * Get a list of tabs that can be discarded. This list includes all tabs in
+   * all windows and is sorted based on a weighting described below.
+   *
+   * @param minInactiveDuration If this value is a number, tabs that were accessed
+   *        in the last |minInactiveDuration| msec are not unloaded even if they
+   *        are least-recently-used.
+   *
+   * @param tabMethods an helper object with methods called by this algorithm.
+   *
+   * The algorithm used is:
+   *   1. Sort all of the tabs by a base weight. Tabs with a higher weight, such as
+   *      those that are pinned or playing audio, will appear at the end. When two
+   *      tabs have the same weight, sort by the order in which they were last.
+   *      recently accessed Tabs that have a weight of NEVER_DISCARD are included in
+   *       the list, but will not be discarded.
+   *   2. Exclude the last X tabs, where X is the value returned by getMinTabCount().
+   *      These tabs are considered to have been recently accessed and are not further
+   *      reweighted. This also saves time when there are less than X tabs open.
+   *   3. Calculate the amount of processes that are used only by each tab, as the
+   *      resources used by these proceses can be freed up if the tab is closed. Sort
+   *      the tabs by the number of unique processes used and add a reweighting factor
+   *      based on this.
+   *   4. Futher reweight based on an approximation of the amount of memory that each
+   *      tab uses.
+   *   5. Combine these weights to produce a final tab discard order, and discard the
+   *      first tab. If this fails, then discard the next tab in the list until no more
+   *      non-discardable tabs are found.
+   *
+   * The tabMethods are used so that unit tests can use false tab objects and
+   * override their behaviour.
+   */
+  async getSortedTabs(
+    minInactiveDuration = kMinInactiveDurationInMs,
+    tabMethods = DefaultTabUnloaderMethods
+  ) {
+    let tabs = [];
+
+    const now = tabMethods.getNow();
+
+    let lowestWeight = 1000;
+    for (let tab of tabMethods.iterateTabs()) {
+      if (
+        typeof minInactiveDuration == "number" &&
+        now - tab.tab.lastAccessed < minInactiveDuration
+      ) {
+        // Skip "fresh" tabs, which were accessed within the specified duration.
+        continue;
+      }
+
+      let weight = determineTabBaseWeight(tab, tabMethods);
+
+      // Don't add tabs that have a weight of -1.
+      if (weight != -1) {
+        tab.weight = weight;
+        tabs.push(tab);
+        if (weight < lowestWeight) {
+          lowestWeight = weight;
+        }
+      }
+    }
+
+    tabs = tabs.sort((a, b) => {
+      if (a.weight != b.weight) {
+        return a.weight - b.weight;
+      }
+
+      return a.tab.lastAccessed - b.tab.lastAccessed;
+    });
+
+    // If the lowest priority tab is not discardable, no need to continue.
+    if (!tabs.length || !this.isDiscardable(tabs[0])) {
+      return tabs;
+    }
+
+    // Determine the lowest weight that the tabs have. The tabs with the
+    // lowest weight (should be most non-selected tabs) will be additionally
+    // weighted by the number of processes and memory that they use.
+    let higherWeightedCount = 0;
+    for (let idx = 0; idx < tabs.length; idx++) {
+      if (tabs[idx].weight != lowestWeight) {
+        higherWeightedCount = tabs.length - idx;
+        break;
+      }
+    }
+
+    // Don't continue to reweight the last few tabs, the number of which is
+    // determined by getMinTabCount. This prevents extra work when there are
+    // only a few tabs, or for the last few tabs that have likely been used
+    // recently.
+    let minCount = tabMethods.getMinTabCount();
+    if (higherWeightedCount < minCount) {
+      higherWeightedCount = minCount;
+    }
+
+    // If |lowestWeightedCount| is 1, no benefit from calculating
+    // the tab's memory and additional weight.
+    const lowestWeightedCount = tabs.length - higherWeightedCount;
+    if (lowestWeightedCount > 1) {
+      let processMap = getAllProcesses(tabs, tabMethods);
+
+      let higherWeightedTabs = tabs.splice(-higherWeightedCount);
+
+      await adjustForResourceUse(tabs, processMap, tabMethods);
+      tabs = tabs.concat(higherWeightedTabs);
+    }
+
+    return tabs;
+  },
+
+  /**
+   * Select and discard one tab.
+   * @returns true if a tab was unloaded, otherwise false.
+   */
+  async unloadLeastRecentlyUsedTab(
+    minInactiveDuration = kMinInactiveDurationInMs
+  ) {
+    const sortedTabs = await this.getSortedTabs(minInactiveDuration);
+
+    for (let tabInfo of sortedTabs) {
+      if (!this.isDiscardable(tabInfo)) {
+        // Since |sortedTabs| is sorted, once we see an undiscardable tab
+        // no need to continue the loop.
+        return false;
+      }
+
+      const remoteType = tabInfo.tab?.linkedBrowser?.remoteType;
+      if (tabInfo.gBrowser.discardBrowser(tabInfo.tab)) {
+        Services.console.logStringMessage(
+          `TabUnloader discarded <${remoteType}>`
+        );
+        tabInfo.tab.updateLastUnloadedByTabUnloader();
+        return true;
+      }
+    }
+    return false;
+  },
+
+  QueryInterface: ChromeUtils.generateQI([
+    "nsIObserver",
+    "nsISupportsWeakReference",
+  ]),
+};
+
+/** Determine the base weight of the tab without accounting for
+ *  resource use
+ * @param tab tab to use
+ * @returns the tab's base weight
+ */
+function determineTabBaseWeight(tab, tabMethods) {
+  let totalWeight = 0;
+
+  for (let criteriaType of criteriaTypes) {
+    let weight = tabMethods[criteriaType[CRITERIA_METHOD]](
+      tab.tab,
+      criteriaType[CRITERIA_WEIGHT]
+    );
+
+    // If a criteria returns -1, then never discard this tab.
+    if (weight == -1) {
+      return -1;
+    }
+
+    totalWeight += weight;
+  }
+
+  return totalWeight;
+}
+
+/**
+ * Constuct a map of the processes that are used by the supplied tabs.
+ * The map will map process ids to an object with two properties:
+ *   count - the number of tabs or subframes that use this process
+ *   topCount - the number of top-level tabs that use this process
+ *   tabSet - the indices of the tabs hosted by this process
+ *
+ * @param tabs array of tabs
+ * @param tabMethods an helper object with methods called by this algorithm.
+ * @returns process map
+ */
+function getAllProcesses(tabs, tabMethods) {
+  // Determine the number of tabs that reference each process. This
+  // is stored in the map 'processMap' where the key is the process
+  // and the value is that number of browsing contexts that use that
+  // process.
+  // XXXndeakin this should be unique processes per tab, in the case multiple
+  // subframes use the same process?
+
+  let processMap = new Map();
+
+  for (let tabIndex = 0; tabIndex < tabs.length; ++tabIndex) {
+    const tab = tabs[tabIndex];
+
+    // The per-tab map will map process ids to an object with three properties:
+    //   isTopLevel - whether the process hosts the tab's top-level frame or not
+    //   frameCount - the number of frames hosted by the process
+    //                (a top frame contributes 2 and a sub frame contributes 1)
+    //   entryToProcessMap - the reference to the object in |processMap|
+    tab.processes = new Map();
+
+    let topLevel = true;
+    for (let pid of tabMethods.iterateProcesses(tab.tab)) {
+      let processInfo = processMap.get(pid);
+      if (processInfo) {
+        processInfo.count++;
+        processInfo.tabSet.add(tabIndex);
+      } else {
+        processInfo = { count: 1, topCount: 0, tabSet: new Set([tabIndex]) };
+        processMap.set(pid, processInfo);
+      }
+
+      let tabProcessEntry = tab.processes.get(pid);
+      if (tabProcessEntry) {
+        ++tabProcessEntry.frameCount;
+      } else {
+        tabProcessEntry = {
+          isTopLevel: topLevel,
+          frameCount: 1,
+          entryToProcessMap: processInfo,
+        };
+        tab.processes.set(pid, tabProcessEntry);
+      }
+
+      if (topLevel) {
+        topLevel = false;
+        processInfo.topCount = processInfo.topCount
+          ? processInfo.topCount + 1
+          : 1;
+        // top-level frame contributes two frame counts
+        ++tabProcessEntry.frameCount;
+      }
+    }
+  }
+
+  return processMap;
+}
+
+/**
+ * Adjust the tab info and reweight the tabs based on the process and memory
+ * use that is used, as described by getSortedTabs
+
+ * @param tabs array of tabs
+ * @param processMap map of processes returned by getAllProcesses
+ * @param tabMethods an helper object with methods called by this algorithm.
+ */
+async function adjustForResourceUse(tabs, processMap, tabMethods) {
+  // The second argument is needed for testing.
+  await tabMethods.calculateMemoryUsage(processMap, tabs);
+
+  let sortWeight = 0;
+  for (let tab of tabs) {
+    tab.sortWeight = ++sortWeight;
+
+    let uniqueCount = 0;
+    let totalMemory = 0;
+    for (const procEntry of tab.processes.values()) {
+      const processInfo = procEntry.entryToProcessMap;
+      if (processInfo.tabSet.size == 1) {
+        uniqueCount++;
+      }
+
+      // Guess how much memory the frame might be using using by dividing
+      // the total memory used by a process by the number of tabs and
+      // frames that are using that process. Assume that any subframes take up
+      // only half as much memory as a process loaded in a top level tab.
+      // So for example, if a process is used in four top level tabs and two
+      // subframes, the top level tabs share 80% of the memory and the subframes
+      // use 20% of the memory.
+      const perFrameMemory =
+        processInfo.memory /
+        (processInfo.topCount * 2 + (processInfo.count - processInfo.topCount));
+      totalMemory += perFrameMemory * procEntry.frameCount;
+    }
+
+    tab.uniqueCount = uniqueCount;
+    tab.memory = totalMemory;
+  }
+
+  tabs.sort((a, b) => {
+    return b.uniqueCount - a.uniqueCount;
+  });
+  sortWeight = 0;
+  for (let tab of tabs) {
+    tab.sortWeight += ++sortWeight;
+    if (tab.uniqueCount > 1) {
+      // If the tab has a number of processes that are only used by this tab,
+      // subtract off an additional amount to the sorting weight value. That
+      // way, tabs that use lots of processes are more likely to be discarded.
+      tab.sortWeight -= tab.uniqueCount - 1;
+    }
+  }
+
+  tabs.sort((a, b) => {
+    return b.memory - a.memory;
+  });
+  sortWeight = 0;
+  for (let tab of tabs) {
+    tab.sortWeight += ++sortWeight;
+  }
+
+  tabs.sort((a, b) => {
+    if (a.sortWeight != b.sortWeight) {
+      return a.sortWeight - b.sortWeight;
+    }
+    return a.tab.lastAccessed - b.tab.lastAccessed;
+  });
+}