// Map from process states to the states we track.
    private static final int[] PROCESS_STATE_TO_STATE = new int[] {
        STATE_PERSISTENT,               // ActivityManager.PROCESS_STATE_PERSISTENT
        STATE_PERSISTENT,               // ActivityManager.PROCESS_STATE_PERSISTENT_UI
        STATE_TOP,                      // ActivityManager.PROCESS_STATE_TOP
        STATE_IMPORTANT_FOREGROUND,     // ActivityManager.PROCESS_STATE_FOREGROUND_SERVICE
        STATE_IMPORTANT_FOREGROUND,     // ActivityManager.PROCESS_STATE_BOUND_FOREGROUND_SERVICE
        STATE_IMPORTANT_FOREGROUND,     // ActivityManager.PROCESS_STATE_IMPORTANT_FOREGROUND
        STATE_IMPORTANT_BACKGROUND,     // ActivityManager.PROCESS_STATE_IMPORTANT_BACKGROUND
        STATE_IMPORTANT_BACKGROUND,     // ActivityManager.PROCESS_STATE_TRANSIENT_BACKGROUND
        STATE_BACKUP,                   // ActivityManager.PROCESS_STATE_BACKUP
        STATE_SERVICE,                  // ActivityManager.PROCESS_STATE_SERVICE
        STATE_RECEIVER,                 // ActivityManager.PROCESS_STATE_RECEIVER
        STATE_TOP,                      // ActivityManager.PROCESS_STATE_TOP_SLEEPING
        STATE_HEAVY_WEIGHT,             // ActivityManager.PROCESS_STATE_HEAVY_WEIGHT
        STATE_HOME,                     // ActivityManager.PROCESS_STATE_HOME
        STATE_LAST_ACTIVITY,            // ActivityManager.PROCESS_STATE_LAST_ACTIVITY
        STATE_CACHED_ACTIVITY,          // ActivityManager.PROCESS_STATE_CACHED_ACTIVITY
        STATE_CACHED_ACTIVITY_CLIENT,   // ActivityManager.PROCESS_STATE_CACHED_ACTIVITY_CLIENT
        STATE_CACHED_ACTIVITY,          // ActivityManager.PROCESS_STATE_CACHED_RECENT
        STATE_CACHED_EMPTY,             // ActivityManager.PROCESS_STATE_CACHED_EMPTY
    }

    /**
     * Standard priority of application threads.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not</b> with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_DEFAULT = 0;

    /*
     * ***************************************
     * ** Keep in sync with utils/threads.h **
     * ***************************************
     */
    
    /**
     * Lowest available thread priority.  Only for those who really, really
     * don't want to run if anything else is happening.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not</b> with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_LOWEST = 19;
    
    /**
     * Standard priority background threads.  This gives your thread a slightly
     * lower than normal priority, so that it will have less chance of impacting
     * the responsiveness of the user interface.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not</b> with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_BACKGROUND = 10;
    
    /**
     * Standard priority of threads that are currently running a user interface
     * that the user is interacting with.  Applications can not normally
     * change to this priority; the system will automatically adjust your
     * application threads as the user moves through the UI.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not</b> with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_FOREGROUND = -2;
    
    /**
     * Standard priority of system display threads, involved in updating
     * the user interface.  Applications can not
     * normally change to this priority.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not</b> with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_DISPLAY = -4;
    
    /**
     * Standard priority of the most important display threads, for compositing
     * the screen and retrieving input events.  Applications can not normally
     * change to this priority.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not</b> with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_URGENT_DISPLAY = -8;

    /**
     * Standard priority of video threads.  Applications can not normally
     * change to this priority.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not</b> with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_VIDEO = -10;

    /**
     * Standard priority of audio threads.  Applications can not normally
     * change to this priority.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not</b> with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_AUDIO = -16;

    /**
     * Standard priority of the most important audio threads.
     * Applications can not normally change to this priority.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not</b> with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_URGENT_AUDIO = -19;

    /**
     * Minimum increment to make a priority more favorable.
     */
    public static final int THREAD_PRIORITY_MORE_FAVORABLE = -1;

    /**
     * Minimum increment to make a priority less favorable.
     */
    public static final int THREAD_PRIORITY_LESS_FAVORABLE = +1;

    /**
     * Default scheduling policy
     * @hide
     */
    public static final int SCHED_OTHER = 0;

    /**
     * First-In First-Out scheduling policy
     * @hide
     */
    public static final int SCHED_FIFO = 1;

    /**
     * Round-Robin scheduling policy
     * @hide
     */
    public static final int SCHED_RR = 2;

    /**
     * Batch scheduling policy
     * @hide
     */
    public static final int SCHED_BATCH = 3;

    /**
     * Idle scheduling policy
     * @hide
     */
    public static final int SCHED_IDLE = 5;

    /**
     * Reset scheduler choice on fork.
     * @hide
     */
     public static final int SCHED_RESET_ON_FORK = 0x40000000;

    /**
     * Default thread group -
     * has meaning with setProcessGroup() only, cannot be used with setThreadGroup().
     * When used with setProcessGroup(), the group of each thread in the process
     * is conditionally changed based on that thread's current priority, as follows:
     * threads with priority numerically less than THREAD_PRIORITY_BACKGROUND
     * are moved to foreground thread group.  All other threads are left unchanged.
     * @hide
     */
    public static final int THREAD_GROUP_DEFAULT = -1;

    /**
     * Background thread group - All threads in
     * this group are scheduled with a reduced share of the CPU.
     * Value is same as constant SP_BACKGROUND of enum SchedPolicy.
     * FIXME rename to THREAD_GROUP_BACKGROUND.
     * @hide
     */
    public static final int THREAD_GROUP_BG_NONINTERACTIVE = 0;

    /**
     * Foreground thread group - All threads in
     * this group are scheduled with a normal share of the CPU.
     * Value is same as constant SP_FOREGROUND of enum SchedPolicy.
     * Not used at this level.
     * @hide
     **/
    private static final int THREAD_GROUP_FOREGROUND = 1;

    /**
     * System thread group.
     * @hide
     **/
    public static final int THREAD_GROUP_SYSTEM = 2;

    /**
     * Application audio thread group.
     * @hide
     **/
    public static final int THREAD_GROUP_AUDIO_APP = 3;

    /**
     * System audio thread group.
     * @hide
     **/
    public static final int THREAD_GROUP_AUDIO_SYS = 4;

    /**
     * Thread group for top foreground app.
     * @hide
     **/
    public static final int THREAD_GROUP_TOP_APP = 5;

    /**
     * Thread group for RT app.
     * @hide
     **/
    public static final int THREAD_GROUP_RT_APP = 6;

    /**
     * Thread group for bound foreground services that should
     * have additional CPU restrictions during screen off
     * @hide
     **/
    public static final int THREAD_GROUP_RESTRICTED = 7;

    public static final int SIGNAL_QUIT = 3;
    public static final int SIGNAL_KILL = 9;
    public static final int SIGNAL_USR1 = 10;

final void updateLruProcessLocked(ProcessRecord app, boolean activityChange,
            ProcessRecord client) {
        final boolean hasActivity = app.activities.size() > 0 || app.hasClientActivities
                || app.treatLikeActivity || app.recentTasks.size() > 0;
        final boolean hasService = false; // not impl yet. app.services.size() > 0;
        if (!activityChange && hasActivity) {
            // The process has activities, so we are only allowing activity-based adjustments
            // to move it.  It should be kept in the front of the list with other
            // processes that have activities, and we don't want those to change their
            // order except due to activity operations.
            return;
        }

        mLruSeq++;
        final long now = SystemClock.uptimeMillis();
        app.lastActivityTime = now;
        ...
        int lrui = mLruProcesses.lastIndexOf(app);

        ...

        if (lrui >= 0) {
            if (lrui < mLruProcessActivityStart) {
                mLruProcessActivityStart--;
            }
            if (lrui < mLruProcessServiceStart) {
                mLruProcessServiceStart--;
            }
            mLruProcesses.remove(lrui);
        }

    
        int nextIndex;
        if (hasActivity) {
            final int N = mLruProcesses.size();
            if ((app.activities.size() == 0 || app.recentTasks.size() > 0)
                    && mLruProcessActivityStart < (N - 1)) {
                // Process doesn't have activities, but has clients with
                // activities...  move it up, but one below the top (the top
                // should always have a real activity).
                if (DEBUG_LRU) Slog.d(TAG_LRU,
                        "Adding to second-top of LRU activity list: " + app);
                mLruProcesses.add(N - 1, app);
                // To keep it from spamming the LRU list (by making a bunch of clients),
                // we will push down any other entries owned by the app.
                final int uid = app.info.uid;
                for (int i = N - 2; i > mLruProcessActivityStart; i--) {
                    ProcessRecord subProc = mLruProcesses.get(i);
                    if (subProc.info.uid == uid) {
                        // We want to push this one down the list.  If the process after
                        // it is for the same uid, however, don't do so, because we don't
                        // want them internally to be re-ordered.
                        if (mLruProcesses.get(i - 1).info.uid != uid) {
                            if (DEBUG_LRU) Slog.d(TAG_LRU,
                                    "Pushing uid " + uid + " swapping at " + i + ": "
                                    + mLruProcesses.get(i) + " : " + mLruProcesses.get(i - 1));
                            ProcessRecord tmp = mLruProcesses.get(i);
                            mLruProcesses.set(i, mLruProcesses.get(i - 1));
                            mLruProcesses.set(i - 1, tmp);
                            i--;
                        }
                    } else {
                        // A gap, we can stop here.
                        break;
                    }
                }
            } else {
                // Process has activities, put it at the very tipsy-top.
                if (DEBUG_LRU) Slog.d(TAG_LRU, "Adding to top of LRU activity list: " + app);
                mLruProcesses.add(app);
            }
            nextIndex = mLruProcessServiceStart;
        } else if (hasService) {
            // Process has services, put it at the top of the service list.
            if (DEBUG_LRU) Slog.d(TAG_LRU, "Adding to top of LRU service list: " + app);
            mLruProcesses.add(mLruProcessActivityStart, app);
            nextIndex = mLruProcessServiceStart;
            mLruProcessActivityStart++;
        } else  {
            // Process not otherwise of interest, it goes to the top of the non-service area.
            int index = mLruProcessServiceStart;
            if (client != null) {
                // If there is a client, don't allow the process to be moved up higher
                // in the list than that client.
                int clientIndex = mLruProcesses.lastIndexOf(client);
                if (DEBUG_LRU && clientIndex < 0) Slog.d(TAG_LRU, "Unknown client " + client
                        + " when updating " + app);
                if (clientIndex <= lrui) {
                    // Don't allow the client index restriction to push it down farther in the
                    // list than it already is.
                    clientIndex = lrui;
                }
                if (clientIndex >= 0 && index > clientIndex) {
                    index = clientIndex;
                }
            }
            if (DEBUG_LRU) Slog.d(TAG_LRU, "Adding at " + index + " of LRU list: " + app);
            mLruProcesses.add(index, app);
            nextIndex = index-1;
            mLruProcessActivityStart++;
            mLruProcessServiceStart++;
        }

        // If the app is currently using a content provider or service,
        // bump those processes as well.
        for (int j=app.connections.size()-1; j>=0; j--) {
            ConnectionRecord cr = app.connections.valueAt(j);
            if (cr.binding != null && !cr.serviceDead && cr.binding.service != null
                    && cr.binding.service.app != null
                    && cr.binding.service.app.lruSeq != mLruSeq
                    && !cr.binding.service.app.persistent) {
                nextIndex = updateLruProcessInternalLocked(cr.binding.service.app, now, nextIndex,
                        "service connection", cr, app);
            }
        }
        for (int j=app.conProviders.size()-1; j>=0; j--) {
            ContentProviderRecord cpr = app.conProviders.get(j).provider;
            if (cpr.proc != null && cpr.proc.lruSeq != mLruSeq && !cpr.proc.persistent) {
                nextIndex = updateLruProcessInternalLocked(cpr.proc, now, nextIndex,
                        "provider reference", cpr, app);
            }
        }
    }

        ...
        // Reset state in all uid records.
        for (int i=mActiveUids.size()-1; i>=0; i--) {
            final UidRecord uidRec = mActiveUids.valueAt(i);
            if (false && DEBUG_UID_OBSERVERS) Slog.i(TAG_UID_OBSERVERS,
                    "Starting update of " + uidRec);
            uidRec.reset();
        }

        mStackSupervisor.rankTaskLayersIfNeeded();

        mAdjSeq++;
        mNewNumServiceProcs = 0;
        mNewNumAServiceProcs = 0;

        final int emptyProcessLimit = mConstants.CUR_MAX_EMPTY_PROCESSES;
        final int cachedProcessLimit = mConstants.CUR_MAX_CACHED_PROCESSES - emptyProcessLimit;

        // Let's determine how many processes we have running vs.
        // how many slots we have for background processes; we may want
        // to put multiple processes in a slot of there are enough of
        // them.
        int numSlots = (ProcessList.CACHED_APP_MAX_ADJ
                - ProcessList.CACHED_APP_MIN_ADJ + 1) / 2;
        int numEmptyProcs = N - mNumNonCachedProcs - mNumCachedHiddenProcs;
        if (numEmptyProcs > cachedProcessLimit) {
            // If there are more empty processes than our limit on cached
            // processes, then use the cached process limit for the factor.
            // This ensures that the really old empty processes get pushed
            // down to the bottom, so if we are running low on memory we will
            // have a better chance at keeping around more cached processes
            // instead of a gazillion empty processes.
            numEmptyProcs = cachedProcessLimit;
        }
        int emptyFactor = numEmptyProcs/numSlots;
        if (emptyFactor < 1) emptyFactor = 1;
        int cachedFactor = (mNumCachedHiddenProcs > 0 ? mNumCachedHiddenProcs : 1)/numSlots;
        if (cachedFactor < 1) cachedFactor = 1;
        int stepCached = 0;
        int stepEmpty = 0;
        int numCached = 0;
        int numEmpty = 0;
        int numTrimming = 0;

        mNumNonCachedProcs = 0;
        mNumCachedHiddenProcs = 0;

        // First update the OOM adjustment for each of the
        // application processes based on their current state.
        int curCachedAdj = ProcessList.CACHED_APP_MIN_ADJ;
        int nextCachedAdj = curCachedAdj+1;
        int curEmptyAdj = ProcessList.CACHED_APP_MIN_ADJ;
        int nextEmptyAdj = curEmptyAdj+2;

        boolean retryCycles = false;

        // need to reset cycle state before calling computeOomAdjLocked because of service connections
        for (int i=N-1; i>=0; i--) {
            ProcessRecord app = mLruProcesses.get(i);
            app.containsCycle = false;
        }

        for (int i=N-1; i>=0; i--) {
            ProcessRecord app = mLruProcesses.get(i);
            if (!app.killedByAm && app.thread != null) {
                app.procStateChanged = false;
                computeOomAdjLocked(app, ProcessList.UNKNOWN_ADJ, TOP_APP, true, now);

                // if any app encountered a cycle, we need to perform an additional loop later
                retryCycles |= app.containsCycle;

                // If we haven't yet assigned the final cached adj
                // to the process, do that now.
                if (app.curAdj >= ProcessList.UNKNOWN_ADJ) {
                    switch (app.curProcState) {
                        case ActivityManager.PROCESS_STATE_CACHED_ACTIVITY:
                        case ActivityManager.PROCESS_STATE_CACHED_ACTIVITY_CLIENT:
                        case ActivityManager.PROCESS_STATE_CACHED_RECENT:
                            // This process is a cached process holding activities...
                            // assign it the next cached value for that type, and then
                            // step that cached level.
                            app.curRawAdj = curCachedAdj;
                            app.curAdj = app.modifyRawOomAdj(curCachedAdj);
                            if (DEBUG_LRU && false) Slog.d(TAG_LRU, "Assigning activity LRU #" + i
                                    + " adj: " + app.curAdj + " (curCachedAdj=" + curCachedAdj
                                    + ")");
                            if (curCachedAdj != nextCachedAdj) {
                                stepCached++;
                                if (stepCached >= cachedFactor) {
                                    stepCached = 0;
                                    curCachedAdj = nextCachedAdj;
                                    nextCachedAdj += 2;
                                    if (nextCachedAdj > ProcessList.CACHED_APP_MAX_ADJ) {
                                        nextCachedAdj = ProcessList.CACHED_APP_MAX_ADJ;
                                    }
                                }
                            }
                            break;
                        default:
                            // For everything else, assign next empty cached process
                            // level and bump that up.  Note that this means that
                            // long-running services that have dropped down to the
                            // cached level will be treated as empty (since their process
                            // state is still as a service), which is what we want.
                            app.curRawAdj = curEmptyAdj;
                            app.curAdj = app.modifyRawOomAdj(curEmptyAdj);
                            if (DEBUG_LRU && false) Slog.d(TAG_LRU, "Assigning empty LRU #" + i
                                    + " adj: " + app.curAdj + " (curEmptyAdj=" + curEmptyAdj
                                    + ")");
                            if (curEmptyAdj != nextEmptyAdj) {
                                stepEmpty++;
                                if (stepEmpty >= emptyFactor) {
                                    stepEmpty = 0;
                                    curEmptyAdj = nextEmptyAdj;
                                    nextEmptyAdj += 2;
                                    if (nextEmptyAdj > ProcessList.CACHED_APP_MAX_ADJ) {
                                        nextEmptyAdj = ProcessList.CACHED_APP_MAX_ADJ;
                                    }
                                }
                            }
                            break;
                    }
                }


            }
        }

        // Cycle strategy:
        // - Retry computing any process that has encountered a cycle.
        // - Continue retrying until no process was promoted.
        // - Iterate from least important to most important.
        int cycleCount = 0;
        while (retryCycles) {
            cycleCount++;
            retryCycles = false;

            for (int i=0; i<N; i++) {
                ProcessRecord app = mLruProcesses.get(i);
                if (!app.killedByAm && app.thread != null && app.containsCycle == true) {
                    app.adjSeq--;
                    app.completedAdjSeq--;
                }
            }

            for (int i=0; i<N; i++) {
                ProcessRecord app = mLruProcesses.get(i);
                if (!app.killedByAm && app.thread != null && app.containsCycle == true) {
                    if (computeOomAdjLocked(app, ProcessList.UNKNOWN_ADJ, TOP_APP, true, now)) {
                        retryCycles = true;
                    }
                }
            }
        }

        for (int i=N-1; i>=0; i--) {
            ProcessRecord app = mLruProcesses.get(i);
            if (!app.killedByAm && app.thread != null) {
                applyOomAdjLocked(app, true, now, nowElapsed);

                // Count the number of process types.
                switch (app.curProcState) {
                    case ActivityManager.PROCESS_STATE_CACHED_ACTIVITY:
                    case ActivityManager.PROCESS_STATE_CACHED_ACTIVITY_CLIENT:
                        mNumCachedHiddenProcs++;
                        numCached++;
                        if (numCached > cachedProcessLimit) {
                            app.kill("cached #" + numCached, true);
                        }
                        break;
                    case ActivityManager.PROCESS_STATE_CACHED_EMPTY:
                        if (numEmpty > mConstants.CUR_TRIM_EMPTY_PROCESSES
                                && app.lastActivityTime < oldTime) {
                            app.kill("empty for "
                                    + ((oldTime + ProcessList.MAX_EMPTY_TIME - app.lastActivityTime)
                                    / 1000) + "s", true);
                        } else {
                            numEmpty++;
                            if (numEmpty > emptyProcessLimit) {
                                app.kill("empty #" + numEmpty, true);
                            }
                        }
                        break;
                    default:
                        mNumNonCachedProcs++;
                        break;
                }

                if (app.isolated && app.services.size() <= 0 && app.isolatedEntryPoint == null) {
                    // If this is an isolated process, there are no services
                    // running in it, and it's not a special process with a
                    // custom entry point, then the process is no longer
                    // needed.  We agressively kill these because we can by
                    // definition not re-use the same process again, and it is
                    // good to avoid having whatever code was running in them
                    // left sitting around after no longer needed.
                    app.kill("isolated not needed", true);
                } else {
                    // Keeping this process, update its uid.
                    final UidRecord uidRec = app.uidRecord;
                    if (uidRec != null) {
                        uidRec.ephemeral = app.info.isInstantApp();
                        if (uidRec.curProcState > app.curProcState) {
                            uidRec.curProcState = app.curProcState;
                        }
                        if (app.foregroundServices) {
                            uidRec.foregroundServices = true;
                        }
                    }
                }

                if (app.curProcState >= ActivityManager.PROCESS_STATE_HOME
                        && !app.killedByAm) {
                    numTrimming++;
                }
            }
        }

        final int numCachedAndEmpty = numCached + numEmpty;
        int memFactor;
        if (numCached <= mConstants.CUR_TRIM_CACHED_PROCESSES
                && numEmpty <= mConstants.CUR_TRIM_EMPTY_PROCESSES) {
            if (numCachedAndEmpty <= ProcessList.TRIM_CRITICAL_THRESHOLD) {
                memFactor = ProcessStats.ADJ_MEM_FACTOR_CRITICAL;
            } else if (numCachedAndEmpty <= ProcessList.TRIM_LOW_THRESHOLD) {
                memFactor = ProcessStats.ADJ_MEM_FACTOR_LOW;
            } else {
                memFactor = ProcessStats.ADJ_MEM_FACTOR_MODERATE;
            }
        } else {
            memFactor = ProcessStats.ADJ_MEM_FACTOR_NORMAL;
        }
        // We always allow the memory level to go up (better).  We only allow it to go
        // down if we are in a state where that is allowed, *and* the total number of processes
        // has gone down since last time.
        if (DEBUG_OOM_ADJ) Slog.d(TAG_OOM_ADJ, "oom: memFactor=" + memFactor
                + " last=" + mLastMemoryLevel + " allowLow=" + mAllowLowerMemLevel
                + " numProcs=" + mLruProcesses.size() + " last=" + mLastNumProcesses);
        if (memFactor > mLastMemoryLevel) {
            if (!mAllowLowerMemLevel || mLruProcesses.size() >= mLastNumProcesses) {
                memFactor = mLastMemoryLevel;
                if (DEBUG_OOM_ADJ) Slog.d(TAG_OOM_ADJ, "Keeping last mem factor!");
            }
        }
        if (memFactor != mLastMemoryLevel) {
            EventLogTags.writeAmMemFactor(memFactor, mLastMemoryLevel);
        }
        mLastMemoryLevel = memFactor;
        mLastNumProcesses = mLruProcesses.size();
        boolean allChanged = mProcessStats.setMemFactorLocked(memFactor, !isSleepingLocked(), now);
        final int trackerMemFactor = mProcessStats.getMemFactorLocked();
        if (memFactor != ProcessStats.ADJ_MEM_FACTOR_NORMAL) {
            if (mLowRamStartTime == 0) {
                mLowRamStartTime = now;
            }
            int step = 0;
            int fgTrimLevel;
            switch (memFactor) {
                case ProcessStats.ADJ_MEM_FACTOR_CRITICAL:
                    fgTrimLevel = ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL;
                    break;
                case ProcessStats.ADJ_MEM_FACTOR_LOW:
                    fgTrimLevel = ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW;
                    break;
                default:
                    fgTrimLevel = ComponentCallbacks2.TRIM_MEMORY_RUNNING_MODERATE;
                    break;
            }
            int factor = numTrimming/3;
            int minFactor = 2;
            if (mHomeProcess != null) minFactor++;
            if (mPreviousProcess != null) minFactor++;
            if (factor < minFactor) factor = minFactor;
            int curLevel = ComponentCallbacks2.TRIM_MEMORY_COMPLETE;
            for (int i=N-1; i>=0; i--) {
                ProcessRecord app = mLruProcesses.get(i);
                if (allChanged || app.procStateChanged) {
                    setProcessTrackerStateLocked(app, trackerMemFactor, now);
                    app.procStateChanged = false;
                }
                if (app.curProcState >= ActivityManager.PROCESS_STATE_HOME
                        && !app.killedByAm) {
                    if (app.trimMemoryLevel < curLevel && app.thread != null) {
                        try {
                            if (DEBUG_SWITCH || DEBUG_OOM_ADJ) Slog.v(TAG_OOM_ADJ,
                                    "Trimming memory of " + app.processName + " to " + curLevel);
                            app.thread.scheduleTrimMemory(curLevel);
                        } catch (RemoteException e) {
                        }
                        if (false) {
                            // For now we won't do this; our memory trimming seems
                            // to be good enough at this point that destroying
                            // activities causes more harm than good.
                            if (curLevel >= ComponentCallbacks2.TRIM_MEMORY_COMPLETE
                                    && app != mHomeProcess && app != mPreviousProcess) {
                                // Need to do this on its own message because the stack may not
                                // be in a consistent state at this point.
                                // For these apps we will also finish their activities
                                // to help them free memory.
                                mStackSupervisor.scheduleDestroyAllActivities(app, "trim");
                            }
                        }
                    }
                    app.trimMemoryLevel = curLevel;
                    step++;
                    if (step >= factor) {
                        step = 0;
                        switch (curLevel) {
                            case ComponentCallbacks2.TRIM_MEMORY_COMPLETE:
                                curLevel = ComponentCallbacks2.TRIM_MEMORY_MODERATE;
                                break;
                            case ComponentCallbacks2.TRIM_MEMORY_MODERATE:
                                curLevel = ComponentCallbacks2.TRIM_MEMORY_BACKGROUND;
                                break;
                        }
                    }
                } else if (app.curProcState == ActivityManager.PROCESS_STATE_HEAVY_WEIGHT
                        && !app.killedByAm) {
                    if (app.trimMemoryLevel < ComponentCallbacks2.TRIM_MEMORY_BACKGROUND
                            && app.thread != null) {
                        try {
                            if (DEBUG_SWITCH || DEBUG_OOM_ADJ) Slog.v(TAG_OOM_ADJ,
                                    "Trimming memory of heavy-weight " + app.processName
                                    + " to " + ComponentCallbacks2.TRIM_MEMORY_BACKGROUND);
                            app.thread.scheduleTrimMemory(
                                    ComponentCallbacks2.TRIM_MEMORY_BACKGROUND);
                        } catch (RemoteException e) {
                        }
                    }
                    app.trimMemoryLevel = ComponentCallbacks2.TRIM_MEMORY_BACKGROUND;
                } else {
                    if ((app.curProcState >= ActivityManager.PROCESS_STATE_IMPORTANT_BACKGROUND
                            || app.systemNoUi) && app.pendingUiClean) {
                        // If this application is now in the background and it
                        // had done UI, then give it the special trim level to
                        // have it free UI resources.
                        final int level = ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN;
                        if (app.trimMemoryLevel < level && app.thread != null) {
                            try {
                                if (DEBUG_SWITCH || DEBUG_OOM_ADJ) Slog.v(TAG_OOM_ADJ,
                                        "Trimming memory of bg-ui " + app.processName
                                        + " to " + level);
                                app.thread.scheduleTrimMemory(level);
                            } catch (RemoteException e) {
                            }
                        }
                        app.pendingUiClean = false;
                    }
                    if (app.trimMemoryLevel < fgTrimLevel && app.thread != null) {
                        try {
                            if (DEBUG_SWITCH || DEBUG_OOM_ADJ) Slog.v(TAG_OOM_ADJ,
                                    "Trimming memory of fg " + app.processName
                                    + " to " + fgTrimLevel);
                            app.thread.scheduleTrimMemory(fgTrimLevel);
                        } catch (RemoteException e) {
                        }
                    }
                    app.trimMemoryLevel = fgTrimLevel;
                }
            }
        } else {
            if (mLowRamStartTime != 0) {
                mLowRamTimeSinceLastIdle += now - mLowRamStartTime;
                mLowRamStartTime = 0;
            }
            for (int i=N-1; i>=0; i--) {
                ProcessRecord app = mLruProcesses.get(i);
                if (allChanged || app.procStateChanged) {
                    setProcessTrackerStateLocked(app, trackerMemFactor, now);
                    app.procStateChanged = false;
                }
                if ((app.curProcState >= ActivityManager.PROCESS_STATE_IMPORTANT_BACKGROUND
                        || app.systemNoUi) && app.pendingUiClean) {
                    if (app.trimMemoryLevel < ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN
                            && app.thread != null) {
                        try {
                            if (DEBUG_SWITCH || DEBUG_OOM_ADJ) Slog.v(TAG_OOM_ADJ,
                                    "Trimming memory of ui hidden " + app.processName
                                    + " to " + ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN);
                            app.thread.scheduleTrimMemory(
                                    ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN);
                        } catch (RemoteException e) {
                        }
                    }
                    app.pendingUiClean = false;
                }
                app.trimMemoryLevel = 0;
            }
        }

        int memFactor;
        if (numCached <= mConstants.CUR_TRIM_CACHED_PROCESSES
                && numEmpty <= mConstants.CUR_TRIM_EMPTY_PROCESSES) {
            if (numCachedAndEmpty <= ProcessList.TRIM_CRITICAL_THRESHOLD) {
                memFactor = ProcessStats.ADJ_MEM_FACTOR_CRITICAL;
            } else if (numCachedAndEmpty <= ProcessList.TRIM_LOW_THRESHOLD) {
                memFactor = ProcessStats.ADJ_MEM_FACTOR_LOW;
            } else {
                memFactor = ProcessStats.ADJ_MEM_FACTOR_MODERATE;
            }
        } else {
            memFactor = ProcessStats.ADJ_MEM_FACTOR_NORMAL;
        }
        ...
        if (memFactor > mLastMemoryLevel) {
            if (!mAllowLowerMemLevel || mLruProcesses.size() >= mLastNumProcesses) {
                memFactor = mLastMemoryLevel;
                ...
            }
        }
       ...

    /**
     * Level for {@link #onTrimMemory(int)}: the process is nearing the end
     * of the background LRU list, and if more memory isn't found soon it will
     * be killed.
     */
    static final int TRIM_MEMORY_COMPLETE = 80;
    
    /**
     * Level for {@link #onTrimMemory(int)}: the process is around the middle
     * of the background LRU list; freeing memory can help the system keep
     * other processes running later in the list for better overall performance.
     */
    static final int TRIM_MEMORY_MODERATE = 60;
    
    /**
     * Level for {@link #onTrimMemory(int)}: the process has gone on to the
     * LRU list.  This is a good opportunity to clean up resources that can
     * efficiently and quickly be re-built if the user returns to the app.
     */
    static final int TRIM_MEMORY_BACKGROUND = 40;
    
    /**
     * Level for {@link #onTrimMemory(int)}: the process had been showing
     * a user interface, and is no longer doing so.  Large allocations with
     * the UI should be released at this point to allow memory to be better
     * managed.
     */
    static final int TRIM_MEMORY_UI_HIDDEN = 20;

    /**
     * Level for {@link #onTrimMemory(int)}: the process is not an expendable
     * background process, but the device is running extremely low on memory
     * and is about to not be able to keep any background processes running.
     * Your running process should free up as many non-critical resources as it
     * can to allow that memory to be used elsewhere.  The next thing that
     * will happen after this is {@link #onLowMemory()} called to report that
     * nothing at all can be kept in the background, a situation that can start
     * to notably impact the user.
     */
    static final int TRIM_MEMORY_RUNNING_CRITICAL = 15;

    /**
     * Level for {@link #onTrimMemory(int)}: the process is not an expendable
     * background process, but the device is running low on memory.
     * Your running process should free up unneeded resources to allow that
     * memory to be used elsewhere.
     */
    static final int TRIM_MEMORY_RUNNING_LOW = 10;

    /**
     * Level for {@link #onTrimMemory(int)}: the process is not an expendable
     * background process, but the device is running moderately low on memory.
     * Your running process may want to release some unneeded resources for
     * use elsewhere.
     */
    static final int TRIM_MEMORY_RUNNING_MODERATE = 5;