void updateCpuStatsNow() {
        synchronized (mProcessCpuTracker) {
            mProcessCpuMutexFree.set(false);
            final long now = SystemClock.uptimeMillis();
            boolean haveNewCpuStats = false;

            if (MONITOR_CPU_USAGE &&
                    mLastCpuTime.get() 
 
< (now-MONITOR_CPU_MIN_TIME)) {
                mLastCpuTime.set(now);
                mProcessCpuTracker.update();
                if (mProcessCpuTracker.hasGoodLastStats()) {
                    haveNewCpuStats = true;
                    //Slog.i(TAG, mProcessCpu.printCurrentState());
                    
 
//Slog.i(TAG, "Total CPU usage: "
                    //        + mProcessCpu.getTotalCpuPercent() + "%");

                    // Slog the cpu usage if the property is set.
                    if ("true".equals(SystemProperties.get("events.cpu"))) {
                        int user = mProcessCpuTracker.getLastUserTime();
                        
 
int system = mProcessCpuTracker.getLastSystemTime();
                        int iowait = mProcessCpuTracker.getLastIoWaitTime();
                        int irq = mProcessCpuTracker.getLastIrqTime();
                        int softIrq = mProcessCpuTracker.getLastSoftIrqTime();
                        int idle = mProcessCpuTracker.getLastIdleTime();

                        int total = user + system + iowait + irq + softIrq + idle;
                        if (total == 0) total = 1;

                        EventLog.writeEvent(EventLogTags.CPU,
                                ((user+system+iowait+irq+softIrq) * 100) / total,
                                (user * 100) / total,
                                (system * 100) / total,
                                (iowait * 100) / total,
                                (irq * 100) / total,
                                (softIrq * 100) / total);
                    }
                }
            }

            final BatteryStatsImpl bstats = mBatteryStatsService.getActiveStatistics();
            synchronized(bstats) {
                synchronized(mPidsSelfLocked) {
                    if (haveNewCpuStats) {
                        if (bstats.startAddingCpuLocked()) {
                            int totalUTime = 0;
                            int totalSTime = 0;
                            final int N = mProcessCpuTracker.countStats();
                            for (int i=0; i<N; i++) {
                                ProcessCpuTracker.Stats st = mProcessCpuTracker.getStats(i);
                                if (!st.working) {
                                    continue;
                                }
                                ProcessRecord pr = mPidsSelfLocked.get(st.pid);
                                totalUTime += st.rel_utime;
                                totalSTime += st.rel_stime;
                                if (pr != null) {
                                    BatteryStatsImpl.Uid.Proc ps = pr.curProcBatteryStats;
                                    if (ps == null || !ps.isActive()) {
                                        pr.curProcBatteryStats = ps = bstats.getProcessStatsLocked(
                                                pr.info.uid, pr.processName);
                                    }
                                    ps.addCpuTimeLocked(st.rel_utime, st.rel_stime);
                                    pr.curCpuTime += st.rel_utime + st.rel_stime;
                                } else {
                                    BatteryStatsImpl.Uid.Proc ps = st.batteryStats;
                                    if (ps == null || !ps.isActive()) {
                                        st.batteryStats = ps = bstats.getProcessStatsLocked(
                                                bstats.mapUid(st.uid), st.name);
                                    }
                                    ps.addCpuTimeLocked(st.rel_utime, st.rel_stime);
                                }
                            }
                            final int userTime = mProcessCpuTracker.getLastUserTime();
                            final int systemTime = mProcessCpuTracker.getLastSystemTime();
                            final int iowaitTime = mProcessCpuTracker.getLastIoWaitTime();
                            final int irqTime = mProcessCpuTracker.getLastIrqTime();
                            final int softIrqTime = mProcessCpuTracker.getLastSoftIrqTime();
                            final int idleTime = mProcessCpuTracker.getLastIdleTime();
                            bstats.finishAddingCpuLocked(totalUTime, totalSTime, userTime,
                                    systemTime, iowaitTime, irqTime, softIrqTime, idleTime);
                        }
                    }
                }

                if (mLastWriteTime < (now-BATTERY_STATS_TIME)) {
                    mLastWriteTime = now;
                    mBatteryStatsService.scheduleWriteToDisk();
                }
            }
        }
    }

【Android N 7.1.1】 ActivityManagerService 獲取cpu狀態