android - 检测是否在具有异构 CPU 架构的设备上运行

Question

我对这个非常具体。我需要知道设备是否有一个 CPU，它有像 ARM's big.LITTLE technology 这样的异构内核。 ，例如，一组4个ARM Cortex-A53 + 另一组4个更强大的ARM Cortex-A72，总共8个内核，基本上是同一芯片中的2个处理器。处理器型号并不重要。

我正在考虑的是读取所有内核的 scaling_max_freq 并将具有不同最大频率的那些分组(然后比较它们)，但我注意到在某些设备中，通往任何内核的路径不是cpu0 实际上是/sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq

的符号链接(symbolic link)

也就是说，如果我尝试读取 cpu3 的 scaling_max_freq，它将链接到 cpu0 的 scaling_max_freq。我想知道在这种情况下我是否可以认为我们不是在异构环境中运行。

CPU类

public final class CPU {
    // To be formatted with specific core number
    private static final String CPU_DIR = "/sys/devices/system/cpu/cpu%d";
    private static final String CPUFREQ_DIR = CPU_DIR + "/cpufreq";
    public static final String SCALING_MAX_FREQ = CPUFREQ_DIR + "/scaling_max_freq";
    private static final String DEFAULT_FREQS = "200000 400000 800000 1200000";

    private CPU() {

    }

    // Here I'd replace 0 with (other) core number
    @NonNull
    public static synchronized String[] getAvailFreqs() {
        String[] split;
        String freqs = FileUtils.readFile(format(SCALING_AVAIL_FREQS, 0), DEFAULT_FREQS);

        try {
            split = freqs.split(" ");
        } catch (Exception e) {
            split = DEFAULT_FREQS.split(" ");
        }
        return split;
    }

    // Here I'd replace 0 with (other) core number
    public static synchronized int getMaxFreq() {
        try {
            return Integer.parseInt(FileUtils.readFile(format(SCALING_MAX_FREQ, 0), "1200000"));
        } catch (Exception ignored){}
        return 1200000;
    }

    private static String format(String format, Object arg) {
        return String.format(Locale.US, format, arg);
    }
}

FileUtils 类

public final class FileUtils {

    private FileUtils() {

    }

    public static String readFile(String pathname, String defaultOutput) {
        return baseReadSingleLineFile(new File(pathname), defaultOutput);
    }

    public static String readFile(File file, String defaultOutput) {
        return baseReadSingleLineFile(file, defaultOutput);
    }

    // Async
    private static String baseReadSingleLineFile(File file, String defaultOutput) {
        String ret = defaultOutput;
        Thread thread = new Thread(() -> {
            if (file.isFile() || file.exists()) {
                if (file.canRead()) {
                    try {
                        FileInputStream inputStream = new FileInputStream(file);
                        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
                        String line = reader.readLine(); // Fisrt line
                        reader.close();
                        inputStream.close();
                        ret = line;
                    } catch (Exception ignored) {}
                } else
                    // Uses cat command
                    ret = RootUtils.readFile(file, defaultOutput);
            }
        });
        thread.start();

        // 3 seconds timeout
        long endTimeMillis = System.currentTimeMillis() + 3000;
        while (thread.isAlive())
            if (System.currentTimeMillis() > endTimeMillis)
                return defaultOutput;

        return ret;
    }
}

Answer 1

您可以解析来自 $ cat/proc/cpuinfo 的结果，在“模型名称”中有描述:

processor   : 0
[...]
model name  : Intel(R) Core(TM) i5 CPU       M 560  @ 2.67GHz
[...]

processor   : 1
[...]

请注意，“cpu MHz”描述的是当前频率，而不是最大值。

引用资料:

https://unix.stackexchange.com/questions/87522/why-do-cpuinfo-cur-freq-and-proc-cpuinfo-report-different-numbers

https://unix.stackexchange.com/questions/146051/number-of-processors-in-proc-cpuinfo

编辑:如果您的操作系统没有返回型号名称，BogoMips 可以用作比较单元(尽管在下面的描述中 Wikipedia 不推荐使用它)。至少您可以使用它来识别您拥有异构架构。

BogoMips (from "bogus" and MIPS) is an unscientific measurement of CPU speed made by the Linux kernel when it boots to calibrate an internal busy-loop. An often-quoted definition of the term is "the number of million times per second a processor can do absolutely nothing".

BogoMips is a value that can be used to verify whether the processor in question is in the proper range of similar processors, i.e. BogoMips represents a processor's clock frequency as well as the potentially present CPU cache. It is not usable for performance comparisons among different CPUs.

Here您可以找到 BogoMips 评级的完整列表。