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[操作系统]如何获取 Android 设备的CPU核数、时钟频率以及内存大小


Device Year Class 的主要功能是根据 CPU核数时钟频率 以及 内存大小 对设备进行分级。代码很简单,只包含两个类:

  • DeviceInfo -> 获取设备参数,
  • YearClass -> 根据参数进行分级。

下表是 Facebook 公司提供的分级标准,其中 Year 栏表示分级结果。

YearCoresClockRAM
20081528MHz192MB
2009n/a600MHz290MB
2010n/a1.0GHz512MB
201121.2GHz1GB
201241.5GHz1.5GB
2013n/a2.0GHz2GB
2014n/a>2GHz>2GB

关于输出年份的计算方法可以参考源码,本文只把一些比较常用的功能抽取出来做一个简要介绍。

获取 CPU 核数

我们都知道,Linux 中的设备都是以文件的形式存在,CPU 也不例外,因此 CPU 的文件个数就等价与核数

Android 的 CPU 设备文件位于 /sys/devices/system/cpu/ 目录,文件名的的格式为 cpu\d+

root@generic_x86_64:/sys/devices/system/cpu # lscpu0cpufreqcpuidlekernel_maxmodaliasofflineonlinepossiblepowerpresentuevent

统计一下文件个数便可以获得 CPU 核数。

public static int getNumberOfCPUCores() { if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.GINGERBREAD_MR1) {  // Gingerbread doesn't support giving a single application access to both cores, but a  // handful of devices (Atrix 4G and Droid X2 for example) were released with a dual-core  // chipset and Gingerbread; that can let an app in the background run without impacting  // the foreground application. But for our purposes, it makes them single core.  return 1; } int cores; try {  cores = new File("/sys/devices/system/cpu/").listFiles(CPU_FILTER).length; } catch (SecurityException e) {  cores = DEVICEINFO_UNKNOWN; } catch (NullPointerException e) {  cores = DEVICEINFO_UNKNOWN; } return cores;}private static final FileFilter CPU_FILTER = new FileFilter() { @Override public boolean accept(File pathname) {  String path = pathname.getName();  //regex is slow, so checking char by char.  if (path.startsWith("cpu")) {   for (int i = 3; i < path.length(); i++) {    if (path.charAt(i) < '0' || path.charAt(i) > '9') {     return false;    }   }   return true;  }  return false; }};
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获取时钟频率

获取时钟频率需要读取系统文件 - /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq 或者/proc/cpuinfo

我的 Android 模拟器中并没有 cpuinfo_max_freq 文件,因此只能读取 /proc/cpuinfo

/proc/cpuinfo 包含了很多 cpu 数据。

processor  : 0vendor_id  : GenuineIntelcpu family : 6model    : 70model name : Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHzstepping  : 1cpu MHz   : 0.000cache size : 1024 KBfdiv_bug  : nohlt_bug   : nof00f_bug  : nocoma_bug  : nofpu   : yesfpu_exception  : yescpuid level : 4wp   : yes

代码如下:

public static int getCPUMaxFreqKHz() { int maxFreq = DEVICEINFO_UNKNOWN; try {  for (int i = 0; i < getNumberOfCPUCores(); i++) {   String filename =     "/sys/devices/system/cpu/cpu" + i + "/cpufreq/cpuinfo_max_freq";   File cpuInfoMaxFreqFile = new File(filename);   if (cpuInfoMaxFreqFile.exists()) {    byte[] buffer = new byte[128];    FileInputStream stream = new FileInputStream(cpuInfoMaxFreqFile);    try {     stream.read(buffer);     int endIndex = 0;     //Trim the first number out of the byte buffer.     while (buffer[endIndex] >= '0' && buffer[endIndex] <= '9'       && endIndex < buffer.length) endIndex++;     String str = new String(buffer, 0, endIndex);     Integer freqBound = Integer.parseInt(str);     if (freqBound > maxFreq) maxFreq = freqBound;    } catch (NumberFormatException e) {     //Fall through and use /proc/cpuinfo.    } finally {     stream.close();    }   }  }  if (maxFreq == DEVICEINFO_UNKNOWN) {   FileInputStream stream = new FileInputStream("/proc/cpuinfo");   try {    int freqBound = parseFileForValue("cpu MHz", stream);    freqBound *= 1000; //MHz -> kHz    if (freqBound > maxFreq) maxFreq = freqBound;   } finally {    stream.close();   }  } } catch (IOException e) {  maxFreq = DEVICEINFO_UNKNOWN; //Fall through and return unknown. } return maxFreq;}
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获取内存大小

如果 SDK 版本大于等于 JELLY_BEAN ,可以通过 ActivityManager 来获取内从大小。

ActivityManager.MemoryInfo memInfo = new ActivityManager.MemoryInfo();ActivityManager am = (ActivityManager) c.getSystemService(Context.ACTIVITY_SERVICE);am.getMemoryInfo(memInfo);
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如果版本低于 JELLY_BEAN ,则只能读取系统文件了。

FileInputStream stream = new FileInputStream("/proc/meminfo");totalMem = parseFileForValue("MemTotal", stream);
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完整代码如下:

@TargetApi(Build.VERSION_CODES.JELLY_BEAN)public static long getTotalMemory(Context c) { // memInfo.totalMem not supported in pre-Jelly Bean APIs. if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {  ActivityManager.MemoryInfo memInfo = new ActivityManager.MemoryInfo();  ActivityManager am = (ActivityManager) c.getSystemService(Context.ACTIVITY_SERVICE);  am.getMemoryInfo(memInfo);  if (memInfo != null) {   return memInfo.totalMem;  } else {   return DEVICEINFO_UNKNOWN;  } } else {  long totalMem = DEVICEINFO_UNKNOWN;  try {   FileInputStream stream = new FileInputStream("/proc/meminfo");   try {    totalMem = parseFileForValue("MemTotal", stream);    totalMem *= 1024;   } finally {    stream.close();   }  } catch (IOException e) {  }  return totalMem; }}
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