Android 进程优先级和 LowMemoryKiller 机制 - 3

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computeOomAdjLocked

// ActivityManagerService.java

private final int computeOomAdjLocked(ProcessRecord app, int cachedAdj, ProcessRecord TOP_APP,
            boolean doingAll, long now) {
        if (mAdjSeq == app.adjSeq) {
            // This adjustment has already been computed.
            return app.curRawAdj;
        }
        if (app.thread == null) {
            app.adjSeq = mAdjSeq;
            app.curSchedGroup = Process.THREAD_GROUP_BG_NONINTERACTIVE;
            app.curProcState = ActivityManager.PROCESS_STATE_CACHED_EMPTY;
            return (app.curAdj=app.curRawAdj=ProcessList.CACHED_APP_MAX_ADJ);
        }
        app.adjTypeCode = ActivityManager.RunningAppProcessInfo.REASON_UNKNOWN;
        app.adjSource = null;
        app.adjTarget = null;
        app.empty = false;
        app.cached = false;
        final int activitiesSize = app.activities.size();
        if (app.maxAdj <= ProcessList.FOREGROUND_APP_ADJ) {  // 前台:adj 0
            // The max adjustment doesn't allow this app to be anything
            // below foreground, so it is not worth doing work for it.
            app.adjType = "fixed";
            app.adjSeq = mAdjSeq;
            app.curRawAdj = app.maxAdj;
            app.foregroundActivities = false;
            app.curSchedGroup = Process.THREAD_GROUP_DEFAULT;
            app.curProcState = ActivityManager.PROCESS_STATE_PERSISTENT;
            // System processes can do UI, and when they do we want to have
            // them trim their memory after the user leaves the UI.  To
            // facilitate this, here we need to determine whether or not it
            // is currently showing UI.
            app.systemNoUi = true;
            if (app == TOP_APP) {
                app.systemNoUi = false;
            } else if (activitiesSize > 0) {
                for (int j = 0; j < activitiesSize; j++) {
                    final ActivityRecord r = app.activities.get(j);
                    if (r.visible) {
                        app.systemNoUi = false;
                    }
                }
            }
            if (!app.systemNoUi) {
                app.curProcState = ActivityManager.PROCESS_STATE_PERSISTENT_UI;
            }
            return (app.curAdj=app.maxAdj);
        }
        app.systemNoUi = false;
        final int PROCESS_STATE_TOP = mTopProcessState;
        
        // 确定进程优先级,从高到低,分配一个合适的 OOM_ADJ
        // Determine the importance of the process, starting with most
        // important to least, and assign an appropriate OOM adjustment.
        int adj;
        int schedGroup;
        int procState;
        boolean foregroundActivities = false;
        BroadcastQueue queue;
        if (app == TOP_APP) { // 1. 前台应用
            // The last app on the list is the foreground app.
            adj = ProcessList.FOREGROUND_APP_ADJ;
            schedGroup = Process.THREAD_GROUP_DEFAULT;
            app.adjType = "top-activity";
            foregroundActivities = true;
            procState = PROCESS_STATE_TOP;
        } else if (app.instrumentationClass != null) { // 2. instrumentation
            // Don't want to kill running instrumentation.
            adj = ProcessList.FOREGROUND_APP_ADJ;
            schedGroup = Process.THREAD_GROUP_DEFAULT;
            app.adjType = "instrumentation";
            procState = ActivityManager.PROCESS_STATE_FOREGROUND_SERVICE;
        } else if ((queue = isReceivingBroadcast(app)) != null) { // 正在接收 Broadcast
            // An app that is currently receiving a broadcast also
            // counts as being in the foreground for OOM killer purposes.
            // It's placed in a sched group based on the nature of the
            // broadcast as reflected by which queue it's active in.
            adj = ProcessList.FOREGROUND_APP_ADJ;
            schedGroup = (queue == mFgBroadcastQueue)
                    ? Process.THREAD_GROUP_DEFAULT : Process.THREAD_GROUP_BG_NONINTERACTIVE;
            app.adjType = "broadcast";
            procState = ActivityManager.PROCESS_STATE_RECEIVER;
        } else if (app.executingServices.size() > 0) { // 正在执行 Service 回调
            // An app that is currently executing a service callback also
            // counts as being in the foreground.
            adj = ProcessList.FOREGROUND_APP_ADJ;
            schedGroup = app.execServicesFg ?
                    Process.THREAD_GROUP_DEFAULT : Process.THREAD_GROUP_BG_NONINTERACTIVE;
            app.adjType = "exec-service";
            procState = ActivityManager.PROCESS_STATE_SERVICE;
            //Slog.i(TAG, "EXEC " + (app.execServicesFg ? "FG" : "BG") + ": " + app);
        } else { // 其他条件暂时认定empty,缓存
            // As far as we know the process is empty.  We may change our mind later.
            schedGroup = Process.THREAD_GROUP_BG_NONINTERACTIVE;
            // At this point we don't actually know the adjustment.  Use the cached adj
            // value that the caller wants us to.
            adj = cachedAdj;
            procState = ActivityManager.PROCESS_STATE_CACHED_EMPTY;
            app.cached = true;
            app.empty = true;
            app.adjType = "cch-empty";
        }
        // Examine all activities if not already foreground.
        if (!foregroundActivities && activitiesSize > 0) {  // 非前台时,继续对所有 Activity 进行判定
            for (int j = 0; j < activitiesSize; j++) {
                final ActivityRecord r = app.activities.get(j);
                if (r.app != app) {
                    Slog.w(TAG, "Wtf, activity " + r + " in proc activity list not using proc "
                            + app + "?!? Using " + r.app + " instead.");
                    continue;
                }
                if (r.visible) {
                    // App has a visible activity; only upgrade adjustment.  
                    // Visible
                    if (adj > ProcessList.VISIBLE_APP_ADJ) {
                        adj = ProcessList.VISIBLE_APP_ADJ;
                        app.adjType = "visible";
                    }
                    if (procState > PROCESS_STATE_TOP) {
                        procState = PROCESS_STATE_TOP;
                    }
                    schedGroup = Process.THREAD_GROUP_DEFAULT;
                    app.cached = false;
                    app.empty = false;
                    foregroundActivities = true;
                    break;
                } else if (r.state == ActivityState.PAUSING || r.state == ActivityState.PAUSED) {
                    if (adj > ProcessList.PERCEPTIBLE_APP_ADJ) {
                        adj = ProcessList.PERCEPTIBLE_APP_ADJ;
                        app.adjType = "pausing";
                    }
                    if (procState > PROCESS_STATE_TOP) {
                        procState = PROCESS_STATE_TOP;
                    }
                    schedGroup = Process.THREAD_GROUP_DEFAULT;
                    app.cached = false;
                    app.empty = false;
                    foregroundActivities = true;
                } else if (r.state == ActivityState.STOPPING) {
                    if (adj > ProcessList.PERCEPTIBLE_APP_ADJ) {
                        adj = ProcessList.PERCEPTIBLE_APP_ADJ;
                        app.adjType = "stopping";
                    }
                    // For the process state, we will at this point consider the
                    // process to be cached.  It will be cached either as an activity
                    // or empty depending on whether the activity is finishing.  We do
                    // this so that we can treat the process as cached for purposes of
                    // memory trimming (determing current memory level, trim command to
                    // send to process) since there can be an arbitrary number of stopping
                    // processes and they should soon all go into the cached state.
                    if (!r.finishing) {
                        if (procState > ActivityManager.PROCESS_STATE_LAST_ACTIVITY) {
                            procState = ActivityManager.PROCESS_STATE_LAST_ACTIVITY;
                        }
                    }
                    app.cached = false;
                    app.empty = false;
                    foregroundActivities = true;
                } else {
                    if (procState > ActivityManager.PROCESS_STATE_CACHED_ACTIVITY) {
                        procState = ActivityManager.PROCESS_STATE_CACHED_ACTIVITY;
                        app.adjType = "cch-act";
                    }
                }
            }
        }
        if (adj > ProcessList.PERCEPTIBLE_APP_ADJ) {
            if (app.foregroundServices) {
                // The user is aware of this app, so make it visible.
                adj = ProcessList.PERCEPTIBLE_APP_ADJ;
                procState = ActivityManager.PROCESS_STATE_FOREGROUND_SERVICE;
                app.cached = false;
                app.adjType = "fg-service";
                schedGroup = Process.THREAD_GROUP_DEFAULT;
            } else if (app.forcingToForeground != null) {
                // The user is aware of this app, so make it visible.
                adj = ProcessList.PERCEPTIBLE_APP_ADJ;
                procState = ActivityManager.PROCESS_STATE_IMPORTANT_FOREGROUND;
                app.cached = false;
                app.adjType = "force-fg";
                app.adjSource = app.forcingToForeground;
                schedGroup = Process.THREAD_GROUP_DEFAULT;
            }
        }
        if (app == mHeavyWeightProcess) {
            if (adj > ProcessList.HEAVY_WEIGHT_APP_ADJ) {
                // We don't want to kill the current heavy-weight process.
                adj = ProcessList.HEAVY_WEIGHT_APP_ADJ;
                schedGroup = Process.THREAD_GROUP_BG_NONINTERACTIVE;
                app.cached = false;
                app.adjType = "heavy";
            }
            if (procState > ActivityManager.PROCESS_STATE_HEAVY_WEIGHT) {
                procState = ActivityManager.PROCESS_STATE_HEAVY_WEIGHT;
            }
        }
        if (app == mHomeProcess) {
            if (adj > ProcessList.HOME_APP_ADJ) {
                // This process is hosting what we currently consider to be the
                // home app, so we don't want to let it go into the background.
                adj = ProcessList.HOME_APP_ADJ;
                schedGroup = Process.THREAD_GROUP_BG_NONINTERACTIVE;
                app.cached = false;
                app.adjType = "home";
            }
            if (procState > ActivityManager.PROCESS_STATE_HOME) {
                procState = ActivityManager.PROCESS_STATE_HOME;
            }
        }
        if (app == mPreviousProcess && app.activities.size() > 0) {
            if (adj > ProcessList.PREVIOUS_APP_ADJ) {
                // This was the previous process that showed UI to the user.
                // We want to try to keep it around more aggressively, to give
                // a good experience around switching between two apps.
                adj = ProcessList.PREVIOUS_APP_ADJ;
                schedGroup = Process.THREAD_GROUP_BG_NONINTERACTIVE;
                app.cached = false;
                app.adjType = "previous";
            }
            if (procState > ActivityManager.PROCESS_STATE_LAST_ACTIVITY) {
                procState = ActivityManager.PROCESS_STATE_LAST_ACTIVITY;
            }
        }
        if (false) Slog.i(TAG, "OOM " + app + ": initial adj=" + adj
                + " reason=" + app.adjType);
        // By default, we use the computed adjustment.  It may be changed if
        // there are applications dependent on our services or providers, but
        // this gives us a baseline and makes sure we don't get into an
        // infinite recursion.
        app.adjSeq = mAdjSeq;
        app.curRawAdj = adj;
        app.hasStartedServices = false;
        if (mBackupTarget != null && app == mBackupTarget.app) {
            // If possible we want to avoid killing apps while they're being backed up
            if (adj > ProcessList.BACKUP_APP_ADJ) {
                if (DEBUG_BACKUP) Slog.v(TAG_BACKUP, "oom BACKUP_APP_ADJ for " + app);
                adj = ProcessList.BACKUP_APP_ADJ;
                if (procState > ActivityManager.PROCESS_STATE_IMPORTANT_BACKGROUND) {
                    procState = ActivityManager.PROCESS_STATE_IMPORTANT_BACKGROUND;
                }
                app.adjType = "backup";
                app.cached = false;
            }
            if (procState > ActivityManager.PROCESS_STATE_BACKUP) {
                procState = ActivityManager.PROCESS_STATE_BACKUP;
            }
        }
        boolean mayBeTop = false;
        for (int is = app.services.size()-1;
                is >= 0 && (adj > ProcessList.FOREGROUND_APP_ADJ
                        || schedGroup == Process.THREAD_GROUP_BG_NONINTERACTIVE
                        || procState > ActivityManager.PROCESS_STATE_TOP);
                is--) {
            ServiceRecord s = app.services.valueAt(is);
            if (s.startRequested) {
                app.hasStartedServices = true;
                if (procState > ActivityManager.PROCESS_STATE_SERVICE) {
                    procState = ActivityManager.PROCESS_STATE_SERVICE;
                }
                if (app.hasShownUi && app != mHomeProcess) {
                    // If this process has shown some UI, let it immediately
                    // go to the LRU list because it may be pretty heavy with
                    // UI stuff.  We'll tag it with a label just to help
                    // debug and understand what is going on.
                    if (adj > ProcessList.SERVICE_ADJ) {
                        app.adjType = "cch-started-ui-services";
                    }
                } else {
                    if (now < (s.lastActivity + ActiveServices.MAX_SERVICE_INACTIVITY)) {
                        // This service has seen some activity within
                        // recent memory, so we will keep its process ahead
                        // of the background processes.
                        if (adj > ProcessList.SERVICE_ADJ) {
                            adj = ProcessList.SERVICE_ADJ;
                            app.adjType = "started-services";
                            app.cached = false;
                        }
                    }
                    // If we have let the service slide into the background
                    // state, still have some text describing what it is doing
                    // even though the service no longer has an impact.
                    if (adj > ProcessList.SERVICE_ADJ) {
                        app.adjType = "cch-started-services";
                    }
                }
            }
            for (int conni = s.connections.size()-1;
                    conni >= 0 && (adj > ProcessList.FOREGROUND_APP_ADJ
                            || schedGroup == Process.THREAD_GROUP_BG_NONINTERACTIVE
                            || procState > ActivityManager.PROCESS_STATE_TOP);
                    conni--) {
                ArrayList<ConnectionRecord> clist = s.connections.valueAt(conni);
                for (int i = 0;
                        i < clist.size() && (adj > ProcessList.FOREGROUND_APP_ADJ
                                || schedGroup == Process.THREAD_GROUP_BG_NONINTERACTIVE
                                || procState > ActivityManager.PROCESS_STATE_TOP);
                        i++) {
                    // XXX should compute this based on the max of
                    // all connected clients.
                    ConnectionRecord cr = clist.get(i);
                    if (cr.binding.client == app) {
                        // Binding to ourself is not interesting.
                        continue;
                    }
                    if ((cr.flags&Context.BIND_WAIVE_PRIORITY) == 0) {
                        ProcessRecord client = cr.binding.client;
                        int clientAdj = computeOomAdjLocked(client, cachedAdj,
                                TOP_APP, doingAll, now);
                        int clientProcState = client.curProcState;
                        if (clientProcState >= ActivityManager.PROCESS_STATE_CACHED_ACTIVITY) {
                            // If the other app is cached for any reason, for purposes here
                            // we are going to consider it empty.  The specific cached state
                            // doesn't propagate except under certain conditions.
                            clientProcState = ActivityManager.PROCESS_STATE_CACHED_EMPTY;
                        }
                        String adjType = null;
                        if ((cr.flags&Context.BIND_ALLOW_OOM_MANAGEMENT) != 0) {
                            // Not doing bind OOM management, so treat
                            // this guy more like a started service.
                            if (app.hasShownUi && app != mHomeProcess) {
                                // If this process has shown some UI, let it immediately
                                // go to the LRU list because it may be pretty heavy with
                                // UI stuff.  We'll tag it with a label just to help
                                // debug and understand what is going on.
                                if (adj > clientAdj) {
                                    adjType = "cch-bound-ui-services";
                                }
                                app.cached = false;
                                clientAdj = adj;
                                clientProcState = procState;
                            } else {
                                if (now >= (s.lastActivity
                                        + ActiveServices.MAX_SERVICE_INACTIVITY)) {
                                    // This service has not seen activity within
                                    // recent memory, so allow it to drop to the
                                    // LRU list if there is no other reason to keep
                                    // it around.  We'll also tag it with a label just
                                    // to help debug and undertand what is going on.
                                    if (adj > clientAdj) {
                                        adjType = "cch-bound-services";
                                    }
                                    clientAdj = adj;
                                }
                            }
                        }
                        if (adj > clientAdj) {
                            // If this process has recently shown UI, and
                            // the process that is binding to it is less
                            // important than being visible, then we don't
                            // care about the binding as much as we care
                            // about letting this process get into the LRU
                            // list to be killed and restarted if needed for
                            // memory.
                            if (app.hasShownUi && app != mHomeProcess
                                    && clientAdj > ProcessList.PERCEPTIBLE_APP_ADJ) {
                                adjType = "cch-bound-ui-services";
                            } else {
                                if ((cr.flags&(Context.BIND_ABOVE_CLIENT
                                        |Context.BIND_IMPORTANT)) != 0) {
                                    adj = clientAdj >= ProcessList.PERSISTENT_SERVICE_ADJ
                                            ? clientAdj : ProcessList.PERSISTENT_SERVICE_ADJ;
                                } else if ((cr.flags&Context.BIND_NOT_VISIBLE) != 0
                                        && clientAdj < ProcessList.PERCEPTIBLE_APP_ADJ
                                        && adj > ProcessList.PERCEPTIBLE_APP_ADJ) {
                                    adj = ProcessList.PERCEPTIBLE_APP_ADJ;
                                } else if (clientAdj > ProcessList.VISIBLE_APP_ADJ) {
                                    adj = clientAdj;
                                } else {
                                    if (adj > ProcessList.VISIBLE_APP_ADJ) {
                                        adj = ProcessList.VISIBLE_APP_ADJ;
                                    }
                                }
                                if (!client.cached) {
                                    app.cached = false;
                                }
                                adjType = "service";
                            }
                        }
                        if ((cr.flags&Context.BIND_NOT_FOREGROUND) == 0) {
                            if (client.curSchedGroup == Process.THREAD_GROUP_DEFAULT) {
                                schedGroup = Process.THREAD_GROUP_DEFAULT;
                            }
                            if (clientProcState <= ActivityManager.PROCESS_STATE_TOP) {
                                if (clientProcState == ActivityManager.PROCESS_STATE_TOP) {
                                    // Special handling of clients who are in the top state.
                                    // We *may* want to consider this process to be in the
                                    // top state as well, but only if there is not another
                                    // reason for it to be running.  Being on the top is a
                                    // special state, meaning you are specifically running
                                    // for the current top app.  If the process is already
                                    // running in the background for some other reason, it
                                    // is more important to continue considering it to be
                                    // in the background state.
                                    mayBeTop = true;
                                    clientProcState = ActivityManager.PROCESS_STATE_CACHED_EMPTY;
                                } else {
                                    // Special handling for above-top states (persistent
                                    // processes).  These should not bring the current process
                                    // into the top state, since they are not on top.  Instead
                                    // give them the best state after that.
                                    if ((cr.flags&Context.BIND_FOREGROUND_SERVICE) != 0) {
                                        clientProcState =
                                                ActivityManager.PROCESS_STATE_BOUND_FOREGROUND_SERVICE;
                                    } else if (mWakefulness
                                                    == PowerManagerInternal.WAKEFULNESS_AWAKE &&
                                            (cr.flags&Context.BIND_FOREGROUND_SERVICE_WHILE_AWAKE)
                                                    != 0) {
                                        clientProcState =
                                                ActivityManager.PROCESS_STATE_BOUND_FOREGROUND_SERVICE;
                                    } else {
                                        clientProcState =
                                                ActivityManager.PROCESS_STATE_IMPORTANT_FOREGROUND;
                                    }
                                }
                            }
                        } else {
                            if (clientProcState <
                                    ActivityManager.PROCESS_STATE_IMPORTANT_BACKGROUND) {
                                clientProcState =
                                        ActivityManager.PROCESS_STATE_IMPORTANT_BACKGROUND;
                            }
                        }
                        if (procState > clientProcState) {
                            procState = clientProcState;
                        }
                        if (procState < ActivityManager.PROCESS_STATE_IMPORTANT_BACKGROUND
                                && (cr.flags&Context.BIND_SHOWING_UI) != 0) {
                            app.pendingUiClean = true;
                        }
                        if (adjType != null) {
                            app.adjType = adjType;
                            app.adjTypeCode = ActivityManager.RunningAppProcessInfo
                                    .REASON_SERVICE_IN_USE;
                            app.adjSource = cr.binding.client;
                            app.adjSourceProcState = clientProcState;
                            app.adjTarget = s.name;
                        }
                    }
                    if ((cr.flags&Context.BIND_TREAT_LIKE_ACTIVITY) != 0) {
                        app.treatLikeActivity = true;
                    }
                    final ActivityRecord a = cr.activity;
                    if ((cr.flags&Context.BIND_ADJUST_WITH_ACTIVITY) != 0) {
                        if (a != null && adj > ProcessList.FOREGROUND_APP_ADJ &&
                                (a.visible || a.state == ActivityState.RESUMED
                                 || a.state == ActivityState.PAUSING)) {
                            adj = ProcessList.FOREGROUND_APP_ADJ;
                            if ((cr.flags&Context.BIND_NOT_FOREGROUND) == 0) {
                                schedGroup = Process.THREAD_GROUP_DEFAULT;
                            }
                            app.cached = false;
                            app.adjType = "service";
                            app.adjTypeCode = ActivityManager.RunningAppProcessInfo
                                    .REASON_SERVICE_IN_USE;
                            app.adjSource = a;
                            app.adjSourceProcState = procState;
                            app.adjTarget = s.name;
                        }
                    }
                }
            }
        }
        for (int provi = app.pubProviders.size()-1;
                provi >= 0 && (adj > ProcessList.FOREGROUND_APP_ADJ
                        || schedGroup == Process.THREAD_GROUP_BG_NONINTERACTIVE
                        || procState > ActivityManager.PROCESS_STATE_TOP);
                provi--) {
            ContentProviderRecord cpr = app.pubProviders.valueAt(provi);
            for (int i = cpr.connections.size()-1;
                    i >= 0 && (adj > ProcessList.FOREGROUND_APP_ADJ
                            || schedGroup == Process.THREAD_GROUP_BG_NONINTERACTIVE
                            || procState > ActivityManager.PROCESS_STATE_TOP);
                    i--) {
                ContentProviderConnection conn = cpr.connections.get(i);
                ProcessRecord client = conn.client;
                if (client == app) {
                    // Being our own client is not interesting.
                    continue;
                }
                int clientAdj = computeOomAdjLocked(client, cachedAdj, TOP_APP, doingAll, now);
                int clientProcState = client.curProcState;
                if (clientProcState >= ActivityManager.PROCESS_STATE_CACHED_ACTIVITY) {
                    // If the other app is cached for any reason, for purposes here
                    // we are going to consider it empty.
                    clientProcState = ActivityManager.PROCESS_STATE_CACHED_EMPTY;
                }
                if (adj > clientAdj) {
                    if (app.hasShownUi && app != mHomeProcess
                            && clientAdj > ProcessList.PERCEPTIBLE_APP_ADJ) {
                        app.adjType = "cch-ui-provider";
                    } else {
                        adj = clientAdj > ProcessList.FOREGROUND_APP_ADJ
                                ? clientAdj : ProcessList.FOREGROUND_APP_ADJ;
                        app.adjType = "provider";
                    }
                    app.cached &= client.cached;
                    app.adjTypeCode = ActivityManager.RunningAppProcessInfo
                            .REASON_PROVIDER_IN_USE;
                    app.adjSource = client;
                    app.adjSourceProcState = clientProcState;
                    app.adjTarget = cpr.name;
                }
                if (clientProcState <= ActivityManager.PROCESS_STATE_TOP) {
                    if (clientProcState == ActivityManager.PROCESS_STATE_TOP) {
                        // Special handling of clients who are in the top state.
                        // We *may* want to consider this process to be in the
                        // top state as well, but only if there is not another
                        // reason for it to be running.  Being on the top is a
                        // special state, meaning you are specifically running
                        // for the current top app.  If the process is already
                        // running in the background for some other reason, it
                        // is more important to continue considering it to be
                        // in the background state.
                        mayBeTop = true;
                        clientProcState = ActivityManager.PROCESS_STATE_CACHED_EMPTY;
                    } else {
                        // Special handling for above-top states (persistent
                        // processes).  These should not bring the current process
                        // into the top state, since they are not on top.  Instead
                        // give them the best state after that.
                        clientProcState =
                                ActivityManager.PROCESS_STATE_BOUND_FOREGROUND_SERVICE;
                    }
                }
                if (procState > clientProcState) {
                    procState = clientProcState;
                }
                if (client.curSchedGroup == Process.THREAD_GROUP_DEFAULT) {
                    schedGroup = Process.THREAD_GROUP_DEFAULT;
                }
            }
            // If the provider has external (non-framework) process
            // dependencies, ensure that its adjustment is at least
            // FOREGROUND_APP_ADJ.
            if (cpr.hasExternalProcessHandles()) {
                if (adj > ProcessList.FOREGROUND_APP_ADJ) {
                    adj = ProcessList.FOREGROUND_APP_ADJ;
                    schedGroup = Process.THREAD_GROUP_DEFAULT;
                    app.cached = false;
                    app.adjType = "provider";
                    app.adjTarget = cpr.name;
                }
                if (procState > ActivityManager.PROCESS_STATE_IMPORTANT_FOREGROUND) {
                    procState = ActivityManager.PROCESS_STATE_IMPORTANT_FOREGROUND;
                }
            }
        }
        if (mayBeTop && procState > ActivityManager.PROCESS_STATE_TOP) {
            // A client of one of our services or providers is in the top state.  We
            // *may* want to be in the top state, but not if we are already running in
            // the background for some other reason.  For the decision here, we are going
            // to pick out a few specific states that we want to remain in when a client
            // is top (states that tend to be longer-term) and otherwise allow it to go
            // to the top state.
            switch (procState) {
                case ActivityManager.PROCESS_STATE_IMPORTANT_FOREGROUND:
                case ActivityManager.PROCESS_STATE_IMPORTANT_BACKGROUND:
                case ActivityManager.PROCESS_STATE_SERVICE:
                    // These all are longer-term states, so pull them up to the top
                    // of the background states, but not all the way to the top state.
                    procState = ActivityManager.PROCESS_STATE_BOUND_FOREGROUND_SERVICE;
                    break;
                default:
                    // Otherwise, top is a better choice, so take it.
                    procState = ActivityManager.PROCESS_STATE_TOP;
                    break;
            }
        }
        if (procState >= ActivityManager.PROCESS_STATE_CACHED_EMPTY) {
            if (app.hasClientActivities) {
                // This is a cached process, but with client activities.  Mark it so.
                procState = ActivityManager.PROCESS_STATE_CACHED_ACTIVITY_CLIENT;
                app.adjType = "cch-client-act";
            } else if (app.treatLikeActivity) {
                // This is a cached process, but somebody wants us to treat it like it has
                // an activity, okay!
                procState = ActivityManager.PROCESS_STATE_CACHED_ACTIVITY;
                app.adjType = "cch-as-act";
            }
        }
        if (adj == ProcessList.SERVICE_ADJ) {
            if (doingAll) {
                app.serviceb = mNewNumAServiceProcs > (mNumServiceProcs/3);
                mNewNumServiceProcs++;
                //Slog.i(TAG, "ADJ " + app + " serviceb=" + app.serviceb);
                if (!app.serviceb) {
                    // This service isn't far enough down on the LRU list to
                    // normally be a B service, but if we are low on RAM and it
                    // is large we want to force it down since we would prefer to
                    // keep launcher over it.
                    if (mLastMemoryLevel > ProcessStats.ADJ_MEM_FACTOR_NORMAL
                            && app.lastPss >= mProcessList.getCachedRestoreThresholdKb()) {
                        app.serviceHighRam = true;
                        app.serviceb = true;
                        //Slog.i(TAG, "ADJ " + app + " high ram!");
                    } else {
                        mNewNumAServiceProcs++;
                        //Slog.i(TAG, "ADJ " + app + " not high ram!");
                    }
                } else {
                    app.serviceHighRam = false;
                }
            }
            if (app.serviceb) {
                adj = ProcessList.SERVICE_B_ADJ;
            }
        }
        app.curRawAdj = adj;
        //Slog.i(TAG, "OOM ADJ " + app + ": pid=" + app.pid +
        //      " adj=" + adj + " curAdj=" + app.curAdj + " maxAdj=" + app.maxAdj);
        if (adj > app.maxAdj) {
            adj = app.maxAdj;
            if (app.maxAdj <= ProcessList.PERCEPTIBLE_APP_ADJ) {
                schedGroup = Process.THREAD_GROUP_DEFAULT;
            }
        }
        // Do final modification to adj.  Everything we do between here and applying
        // the final setAdj must be done in this function, because we will also use
        // it when computing the final cached adj later.  Note that we don't need to
        // worry about this for max adj above, since max adj will always be used to
        // keep it out of the cached vaues.
        app.curAdj = app.modifyRawOomAdj(adj);
        app.curSchedGroup = schedGroup;
        app.curProcState = procState;
        app.foregroundActivities = foregroundActivities;
        return app.curRawAdj;
    }

applyOomAdjLocked

private final boolean applyOomAdjLocked(ProcessRecord app, boolean doingAll, long now,
            long nowElapsed) {
        boolean success = true;
        if (app.curRawAdj != app.setRawAdj) {
            app.setRawAdj = app.curRawAdj;
        }
        int changes = 0;
        if (app.curAdj != app.setAdj) {
            ProcessList.setOomAdj(app.pid, app.info.uid, app.curAdj);
            if (DEBUG_SWITCH || DEBUG_OOM_ADJ) Slog.v(TAG_OOM_ADJ,
                    "Set " + app.pid + " " + app.processName + " adj " + app.curAdj + ": "
                    + app.adjType);
            app.setAdj = app.curAdj;
        }
        if (app.setSchedGroup != app.curSchedGroup) {
            app.setSchedGroup = app.curSchedGroup;
            if (DEBUG_SWITCH || DEBUG_OOM_ADJ) Slog.v(TAG_OOM_ADJ,
                    "Setting process group of " + app.processName
                    + " to " + app.curSchedGroup);
            if (app.waitingToKill != null && app.curReceiver == null
                    && app.setSchedGroup == Process.THREAD_GROUP_BG_NONINTERACTIVE) {
                app.kill(app.waitingToKill, true);
                success = false;
            } else {
                if (true) {
                    long oldId = Binder.clearCallingIdentity();
                    try {
                        Process.setProcessGroup(app.pid, app.curSchedGroup);
                    } catch (Exception e) {
                        Slog.w(TAG, "Failed setting process group of " + app.pid
                                + " to " + app.curSchedGroup);
                        e.printStackTrace();
                    } finally {
                        Binder.restoreCallingIdentity(oldId);
                    }
                } else {
                    if (app.thread != null) {
                        try {
                            app.thread.setSchedulingGroup(app.curSchedGroup);
                        } catch (RemoteException e) {
                        }
                    }
                }
                Process.setSwappiness(app.pid,
                        app.curSchedGroup <= Process.THREAD_GROUP_BG_NONINTERACTIVE);
            }
        }
        if (app.repForegroundActivities != app.foregroundActivities) {
            app.repForegroundActivities = app.foregroundActivities;
            changes |= ProcessChangeItem.CHANGE_ACTIVITIES;
        }
        if (app.repProcState != app.curProcState) {
            app.repProcState = app.curProcState;
            changes |= ProcessChangeItem.CHANGE_PROCESS_STATE;
            if (app.thread != null) {
                try {
                    if (false) {
                        //RuntimeException h = new RuntimeException("here");
                        Slog.i(TAG, "Sending new process state " + app.repProcState
                                + " to " + app /*, h*/);
                    }
                    app.thread.setProcessState(app.repProcState);
                } catch (RemoteException e) {
                }
            }
        }
        if (app.setProcState == ActivityManager.PROCESS_STATE_NONEXISTENT
                || ProcessList.procStatesDifferForMem(app.curProcState, app.setProcState)) {
            if (false && mTestPssMode && app.setProcState >= 0 && app.lastStateTime <= (now-200)) {
                // Experimental code to more aggressively collect pss while
                // running test...  the problem is that this tends to collect
                // the data right when a process is transitioning between process
                // states, which well tend to give noisy data.
                long start = SystemClock.uptimeMillis();
                long pss = Debug.getPss(app.pid, mTmpLong, null);
                recordPssSampleLocked(app, app.curProcState, pss, mTmpLong[0], now);
                mPendingPssProcesses.remove(app);
                Slog.i(TAG, "Recorded pss for " + app + " state " + app.setProcState
                        + " to " + app.curProcState + ": "
                        + (SystemClock.uptimeMillis()-start) + "ms");
            }
            app.lastStateTime = now;
            app.nextPssTime = ProcessList.computeNextPssTime(app.curProcState, true,
                    mTestPssMode, isSleeping(), now);
            if (DEBUG_PSS) Slog.d(TAG_PSS, "Process state change from "
                    + ProcessList.makeProcStateString(app.setProcState) + " to "
                    + ProcessList.makeProcStateString(app.curProcState) + " next pss in "
                    + (app.nextPssTime-now) + ": " + app);
        } else {
            if (now > app.nextPssTime || (now > (app.lastPssTime+ProcessList.PSS_MAX_INTERVAL)
                    && now > (app.lastStateTime+ProcessList.minTimeFromStateChange(
                    mTestPssMode)))) {
                requestPssLocked(app, app.setProcState);
                app.nextPssTime = ProcessList.computeNextPssTime(app.curProcState, false,
                        mTestPssMode, isSleeping(), now);
            } else if (false && DEBUG_PSS) Slog.d(TAG_PSS,
                    "Not requesting PSS of " + app + ": next=" + (app.nextPssTime-now));
        }
        if (app.setProcState != app.curProcState) {
            if (DEBUG_SWITCH || DEBUG_OOM_ADJ) Slog.v(TAG_OOM_ADJ,
                    "Proc state change of " + app.processName
                            + " to " + app.curProcState);
            boolean setImportant = app.setProcState < ActivityManager.PROCESS_STATE_SERVICE;
            boolean curImportant = app.curProcState < ActivityManager.PROCESS_STATE_SERVICE;
            if (setImportant && !curImportant) {
                // This app is no longer something we consider important enough to allow to
                // use arbitrary amounts of battery power.  Note
                // its current wake lock time to later know to kill it if
                // it is not behaving well.
                BatteryStatsImpl stats = mBatteryStatsService.getActiveStatistics();
                synchronized (stats) {
                    app.lastWakeTime = stats.getProcessWakeTime(app.info.uid,
                            app.pid, nowElapsed);
                }
                app.lastCpuTime = app.curCpuTime;
            }
            // Inform UsageStats of important process state change
            // Must be called before updating setProcState
            maybeUpdateUsageStatsLocked(app, nowElapsed);
            app.setProcState = app.curProcState;
            if (app.setProcState >= ActivityManager.PROCESS_STATE_HOME) {
                app.notCachedSinceIdle = false;
            }
            if (!doingAll) {
                setProcessTrackerStateLocked(app, mProcessStats.getMemFactorLocked(), now);
            } else {
                app.procStateChanged = true;
            }
        } else if (app.reportedInteraction && (nowElapsed-app.interactionEventTime)
                > USAGE_STATS_INTERACTION_INTERVAL) {
            // For apps that sit around for a long time in the interactive state, we need
            // to report this at least once a day so they don't go idle.
            maybeUpdateUsageStatsLocked(app, nowElapsed);
        }
        if (changes != 0) {
            if (DEBUG_PROCESS_OBSERVERS) Slog.i(TAG_PROCESS_OBSERVERS,
                    "Changes in " + app + ": " + changes);
            int i = mPendingProcessChanges.size()-1;
            ProcessChangeItem item = null;
            while (i >= 0) {
                item = mPendingProcessChanges.get(i);
                if (item.pid == app.pid) {
                    if (DEBUG_PROCESS_OBSERVERS) Slog.i(TAG_PROCESS_OBSERVERS,
                            "Re-using existing item: " + item);
                    break;
                }
                i--;
            }
            if (i < 0) {
                // No existing item in pending changes; need a new one.
                final int NA = mAvailProcessChanges.size();
                if (NA > 0) {
                    item = mAvailProcessChanges.remove(NA-1);
                    if (DEBUG_PROCESS_OBSERVERS) Slog.i(TAG_PROCESS_OBSERVERS,
                            "Retrieving available item: " + item);
                } else {
                    item = new ProcessChangeItem();
                    if (DEBUG_PROCESS_OBSERVERS) Slog.i(TAG_PROCESS_OBSERVERS,
                            "Allocating new item: " + item);
                }
                item.changes = 0;
                item.pid = app.pid;
                item.uid = app.info.uid;
                if (mPendingProcessChanges.size() == 0) {
                    if (DEBUG_PROCESS_OBSERVERS) Slog.i(TAG_PROCESS_OBSERVERS,
                            "*** Enqueueing dispatch processes changed!");
                    mUiHandler.obtainMessage(DISPATCH_PROCESSES_CHANGED).sendToTarget();
                }
                mPendingProcessChanges.add(item);
            }
            item.changes |= changes;
            item.processState = app.repProcState;
            item.foregroundActivities = app.repForegroundActivities;
            if (DEBUG_PROCESS_OBSERVERS) Slog.i(TAG_PROCESS_OBSERVERS,
                    "Item " + Integer.toHexString(System.identityHashCode(item))
                    + " " + app.toShortString() + ": changes=" + item.changes
                    + " procState=" + item.processState
                    + " foreground=" + item.foregroundActivities
                    + " type=" + app.adjType + " source=" + app.adjSource
                    + " target=" + app.adjTarget);
        }
        return success;
    }
    private final void enqueueUidChangeLocked(UidRecord uidRec, boolean gone) {
        if (uidRec.pendingChange == null) {
            if (mPendingUidChanges.size() == 0) {
                if (DEBUG_UID_OBSERVERS) Slog.i(TAG_UID_OBSERVERS,
                        "*** Enqueueing dispatch uid changed!");
                mUiHandler.obtainMessage(DISPATCH_UIDS_CHANGED_MSG).sendToTarget();
            }
            final int NA = mAvailUidChanges.size();
            if (NA > 0) {
                uidRec.pendingChange = mAvailUidChanges.remove(NA-1);
                if (DEBUG_UID_OBSERVERS) Slog.i(TAG_UID_OBSERVERS,
                        "Retrieving available item: " + uidRec.pendingChange);
            } else {
                uidRec.pendingChange = new UidRecord.ChangeItem();
                if (DEBUG_UID_OBSERVERS) Slog.i(TAG_UID_OBSERVERS,
                        "Allocating new item: " + uidRec.pendingChange);
            }
            uidRec.pendingChange.uidRecord = uidRec;
            uidRec.pendingChange.uid = uidRec.uid;
            mPendingUidChanges.add(uidRec.pendingChange);
        }
        uidRec.pendingChange.gone = gone;
        uidRec.pendingChange.processState = uidRec.setProcState;
    }

NEXT:http://www.jianshu.com/p/94d1cd553c44

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