How to get the number of cores of an android device

Question

I was looking to determine(or count) the number of cores in the embedded processor of android device.

I tried using /proc/cpuinfo, but it is not return

Answer 1

You may use a combination of above answer with this one. This way it will perform faster on devices running API 17+ as this method is much faster than filtering out files.

private int getNumberOfCores() {
    if(Build.VERSION.SDK_INT >= 17) {
        return Runtime.getRuntime().availableProcessors()
    }
    else {
       // Use saurabh64's answer
       return getNumCoresOldPhones();
    }
}

/**
 * Gets the number of cores available in this device, across all processors.
 * Requires: Ability to peruse the filesystem at "/sys/devices/system/cpu"
 * @return The number of cores, or 1 if failed to get result
 */
private int getNumCoresOldPhones() {
    //Private Class to display only CPU devices in the directory listing
    class CpuFilter implements FileFilter {
        @Override
        public boolean accept(File pathname) {
            //Check if filename is "cpu", followed by a single digit number
            if(Pattern.matches("cpu[0-9]+", pathname.getName())) {
                return true;
            }
            return false;
        }      
    }

    try {
        //Get directory containing CPU info
        File dir = new File("/sys/devices/system/cpu/");
        //Filter to only list the devices we care about
        File[] files = dir.listFiles(new CpuFilter());
        //Return the number of cores (virtual CPU devices)
        return files.length;
    } catch(Exception e) {
        //Default to return 1 core
        return 1;
    }
}

public int availableProcessors ()

Added in API level 1 Returns the number of processor cores available to the VM, at least 1. Traditionally this returned the number currently online, but many mobile devices are able to take unused cores offline to save power, so releases newer than Android 4.2 (Jelly Bean) return the maximum number of cores that could be made available if there were no power or heat constraints.

Also there is information about number of cores inside a file located in /sys/devices/system/cpu/present It reports the number of available CPUs in the following format:

• 0 -> single CPU/core
• 0-1 -> two CPUs/cores
• 0-3 -> four CPUs/cores
• 0-7 -> eight CPUs/cores

etc.

Also please check what is inside /sys/devices/system/cpu/possible on a note 3

Both files have r--r--r-- or 444 file permissions set on them, so you should be able to read them without a rooted device in code.

EDIT: Posting code to help you out

 private void printNumberOfCores() {
        printFile("/sys/devices/system/cpu/present");
        printFile("/sys/devices/system/cpu/possible");

    }

    private void printFile(String path) {
        InputStream inputStream = null;
        try {
            inputStream = new FileInputStream(path);
            if (inputStream != null) {

                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                String line;

                do {
                    line = bufferedReader.readLine();
                    Log.d(path, line);
                } while (line != null);
            }
        } catch (Exception e) {

        } finally {
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                }
            }
        }
    }

With the result

D//sys/devices/system/cpu/present﹕ 0-3
D//sys/devices/system/cpu/possible﹕ 0-3

The test was run on OnePlus One running BlissPop ROM with Android v5.1.1 and it prints as it should. Please try on your Samsung

Answer 2

Firstly, it seems like this is not possible, here is some information on this:

We will use the Samsung Exynos 5 Octa CPU as an example for this thread, but generally any ARM processor will work the same.

The Samsung Exynos 5 Octa CPU has 8 CPU cores. but in reality it has two processes with 4 cores each. This is called big.LITTLE. You have 1 fast processor and 1 power efficient processor.

Within the Exynos 5 CPU it has two different CPUs in built, a Cortex a15 and a Cortex a7...

Within big.LITTLE both CPUs cannot run at the same time, only one CPU can be active at any given time...

But there is also something called "big.LITTLE mp" in which both CPU's can be active at the same time, but here is the catch (again!) Only FOUR cores can be active to the software at any given time. Here is an image to explain this a bit better:

Now as you can see, a single CPU core is used from the more powerful processor here and then the other four cores are active from the more energy efficient a7 CPU cluster.

You can read more about the big.LITTLE architecture here : http://www.arm.com/products/processors/technologies/biglittleprocessing.php

You can read more about the big.LITTLE mp architecture here: http://www.arm.com/products/processors/technologies/biglittleprocessing.php

What you want to find out now, is if it is possible to know if the CPU architecture is Big.LITTLE or BIG.LITTLE mp. Then see if you can directly find out the CPU count from each individual CPU, but I cannot find any relevant code. There is a lot of documentation on ARMs website, but I am not too sure if it is possible to get this information. Either way though, only 4 CPU cores can be used therefor the code you have is technically correct as that is the number of useable cores.

I hope this helped, if you have any questions or want anything clearing up then let me know. There is a lot of information out there