Android中的dumpsys cpuinfo:解释此命令的结果

Question

我正在查看以下命令"adb shell dumpsys cpuinfo",我想知道这些报告的值是否是前一次的平均值？

    D:\Android_Dev\Android_sdk\platform-tools>adb shell dumpsys cpuinfo
Load: 4.03 / 3.43 / 2.44
CPU usage from 23770ms to 16630ms ago:
  58% 1844/logd: 58% user + 0% kernel / faults: 3 minor
  50% 3895/com.google.android.wearable.app:ui: 41% user + 9.3% kernel / faults: 1798 minor
  26% 1864/adbd: 2.8% user + 23% kernel / faults: 1243 minor
  22% 4880/logcat: 7.8% user + 15% kernel
  9.7% 7834/kworker/0:2: 0% user + 9.7% kernel
  4.9% 2198/system_server: 2.6% user + 2.2% kernel / faults: 76 minor

我的问题如下:

1. 故障代表什么？
2. 这些百分比值代表什么,因为它们不加100？
3. 这些百分比值是各个过程的平均值,例如logd的58%？
4. CPU usage from 23770ms to 16630ms ago:这是什么意思 ？这是否意味着这些值是过去23到16秒的平均值？

Answer 1

adb shell dumpsys cpuinfo

显示来自/ proc/stat和/ proc /(pid)/ stat的信息

1.故障在这里代表什么？

页面错误.
轻微故障的"次要".

来自ProcessCpuTracker.java

collectStats(...) {
  ...
  final long[] procStats = mProcessStatsData;
  if (!Process.readProcFile(st.statFile.toString(),
  PROCESS_STATS_FORMAT, null, procStats, null)) {
  continue;
  }
  ...
  final long minfaults = procStats[PROCESS_STAT_MINOR_FAULTS];
  final long majfaults = procStats[PROCESS_STAT_MAJOR_FAULTS];
}

private static final int[] PROCESS_STATS_FORMAT = new int[] {
  ...
  PROC_SPACE_TERM|PROC_OUT_LONG,                  // 10: minor faults
  ...
  PROC_SPACE_TERM|PROC_OUT_LONG,                  // 12: major faults
  ...
};

它们是/ proc /(pid)/ stat data [9]和data [11].

2.他们不加100

http://blog.scoutapp.com/articles/2009/07/31/understanding-load-averages
(解释dumpsys cpuinfo的链接页面)

使用多处理器系统,总和可以超过100%.

3.这些百分比值是各个过程的平均值

来自ProcessCpuTracker.java

printProcessCPU(...) {
  ...
  printRatio(pw, user+system+iowait+irq+softIrq, totalTime);
  ...
}

打印第2个参数(用户+ ...)/第3个参数(totalTime).

4.CPU使用从23770ms到16630ms之前

时间基于ProcessCpuTracker缓存的统计数据更新的时间.

来自ProcessCpuTracker.java

update() {
  final long nowUptime = SystemClock.uptimeMillis();
  ...
  mLastSampleTime = mCurrentSampleTime;
  mCurrentSampleTime = nowUptime;
  ...
}

[相关来源]
https://android.googlesource.com/platform/frameworks/native/+/master/cmds/dumpsys/dumpsys.cpp
main()=> service-> dump()

https://github.com/android/platform_frameworks_base/blob/master/services/core/java/com/android/server/am/ActivityManagerService.java
CpuBinder.dump()被称为
mProcessCpuThread更新stat缓存.(调用updateCpuStatsNow())

printps : //github.com/android/platform_frameworks_base/blob/master/core/java/com/android/internal/os/ProcessCpuTracker.java printCurrentLoad()打印CPU负载
printCurrentState()打印每个进程统计信息