Get memory and CPU usage

Question

I would like to get the total physical memory, the CPU usage, and and the amount of memory being used. I have looked into Runtime.freeMemory(), but that isn't the free memory for the whole system.

Accessory

possible duplicate of How to monitor the computer's cpu, memory, and disk usage in Java? – Coracle

did you go through the list of previous questions about this? look at the "related" section on the right of this page. Please specify what exactly you're missing if it's not covered in there already. – Coracle

also a duplicate of #1011563 – Demurral

-1: Clearly no research performed here. There are a gazillion ways to find out this information, including half a gazillion right here on this page, under "Related". The same list appeared as you wrote your post. – Pyromagnetic

Answer 1

I know I'm late with my answer, but I think this code is interesting. This is an adaptation of "closed" code, and should be revised before aplying directly:

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.lang.Process;
import java.lang.Runtime;
import java.util.HashMap;

/**
 * SystemStatusReader is a collection of methods to read system status (cpu and memory)
 * 
 * @author Andreu Correa Casablanca
 */
public class SystemStatusReader
{
    public static final int CONSERVATIVE    = 0;
    public static final int AVERAGE     = 1;
    public static final int OPTIMISTIC  = 2;

    /**
     * cpuUsage gives us the percentage of cpu usage
     * 
     * mpstat -P ALL out stream example:
     *
     *  Linux 3.2.0-30-generic (castarco-laptop)    10/09/12    _x86_64_    (2 CPU)                 - To discard
     *                                                                                              - To discard
     *  00:16:30     CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest   %idle    - To discard
     *  00:16:30     all   17,62    0,03    3,55    0,84    0,00    0,03    0,00    0,00   77,93
     *  00:16:30       0   17,36    0,05    3,61    0,83    0,00    0,05    0,00    0,00   78,12
     *  00:16:30       1   17,88    0,02    3,49    0,86    0,00    0,01    0,00    0,00   77,74
     * 
     * @param measureMode Indicates if we want optimistic, convervative or average measurements.
     */
    public static Double cpuUsage (int measureMode) throws Exception {

        BufferedReader mpstatReader = null;

        String      mpstatLine;
        String[]    mpstatChunkedLine;

        Double      selected_idle;

        try {
            Runtime runtime = Runtime.getRuntime();
            Process mpstatProcess = runtime.exec("mpstat -P ALL");

            mpstatReader = new BufferedReader(new InputStreamReader(mpstatProcess.getInputStream()));

            // We discard the three first lines
            mpstatReader.readLine();
            mpstatReader.readLine();
            mpstatReader.readLine();

            mpstatLine = mpstatReader.readLine();
            if (mpstatLine == null) {
                throw new Exception("mpstat didn't work well");
            } else if (measureMode == SystemStatusReader.AVERAGE) {
                mpstatChunkedLine = mpstatLine.replaceAll(",", ".").split("\\s+");
                selected_idle = Double.parseDouble(mpstatChunkedLine[10]);
            } else {
                selected_idle   = (measureMode == SystemStatusReader.CONSERVATIVE)?200.:0.;
                Double candidate_idle;

                int i = 0;
                while((mpstatLine = mpstatReader.readLine()) != null) {
                    mpstatChunkedLine = mpstatLine.replaceAll(",", ".").split("\\s+");
                    candidate_idle = Double.parseDouble(mpstatChunkedLine[10]);

                    if (measureMode == SystemStatusReader.CONSERVATIVE) {
                        selected_idle = (selected_idle < candidate_idle)?selected_idle:candidate_idle;
                    } else if (measureMode == SystemStatusReader.OPTIMISTIC) {
                        selected_idle = (selected_idle > candidate_idle)?selected_idle:candidate_idle;
                    }
                    ++i;
                }
                if (i == 0) {
                    throw new Exception("mpstat didn't work well");
                }
            }
        } catch (Exception e) {
            throw e; // It's not desirable to handle the exception here
        } finally {
            if (mpstatReader != null) try {
                mpstatReader.close();
            } catch (IOException e) {
                // Do nothing
            }
        }

        return  100-selected_idle;
    }

    /**
     * memoryUsage gives us data about memory usage (RAM and SWAP)
     */
    public static HashMap<String, Integer> memoryUsage () throws Exception {
        BufferedReader freeReader = null;

        String      freeLine;
        String[]    freeChunkedLine;

        HashMap<String, Integer> usageData = new HashMap<String, Integer>();

        try {
            Runtime runtime = Runtime.getRuntime();
            Process freeProcess = runtime.exec("free -k"); // We measure memory in kilobytes to obtain a greater granularity

            freeReader = new BufferedReader(new InputStreamReader(freeProcess.getInputStream()));

            // We discard the first line
            freeReader.readLine();

            freeLine = freeReader.readLine();
            if (freeLine == null) {
                throw new Exception("free didn't work well");
            }
            freeChunkedLine = freeLine.split("\\s+");

            usageData.put("total", Integer.parseInt(freeChunkedLine[1]));

            freeLine = freeReader.readLine();
            if (freeLine == null) {
                throw new Exception("free didn't work well");
            }
            freeChunkedLine = freeLine.split("\\s+");

            usageData.put("used", Integer.parseInt(freeChunkedLine[2]));

            freeLine = freeReader.readLine();
            if (freeLine == null) {
                throw new Exception("free didn't work well");
            }
            freeChunkedLine = freeLine.split("\\s+");

            usageData.put("swap_total", Integer.parseInt(freeChunkedLine[1]));
            usageData.put("swap_used", Integer.parseInt(freeChunkedLine[2]));
        } catch (Exception e) {
            throw e;
        } finally {
            if (freeReader != null) try {
                freeReader.close();
            } catch (IOException e) {
                // Do nothing
            }
        }

        return usageData;
    }
}

Shrink

This would only work on a *nix system, wouldn't work on Windows. – Bistort

Answer 2

You can use SIGAR (http://support.hyperic.com/display/SIGAR/Home). I believe this is cross platform (I've only tried it on Windows) and I know it works (because I've tried it).

Javadoc: http://www.hyperic.com/support/docs/sigar/

Binaries: http://support.hyperic.com/display/SIGAR/Home#Home-binaries

Purpleness

The javadoc doesn't match the binarys. I can't seem to find the CpuPerc class in the JAR file i downloaded. – Bridgetbridgetown

@Bridgetbridgetown Weird. I have no idea what's wrong. It seems like those links are still up to date. I know they have to use native code, so perhaps your OS doesn't have an interface with SIGAR? I'd suggest double checking the little things -- are you on the latest version? Do you have the right imports? Etc. – Purpleness

Answer 3

Memory and CPU.

CPU example:

static final ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();
      ...

    long start = threadBean.getCurrentThreadCpuTime();
     for (int i = 0; i < 10000000; i++) {
        ...
     }
    long finish = threadBean.getCurrentThreadCpuTime();

Valvate

Answer 4

On Linux you could open /proc/meminfo as a text file and parse the result.

Eton

I need a cross-platform solution – Accessory

Answer 5

Use JMX via 'jconsole', if this if for interactive use. It displays nice realtime graphs, and lots of other diagnostic information.

Cristencristi

Can you enlighten us on what the Java libraries and methods are that JMX uses to get memory info, and in our own programs, how can we use those methods in the same way that JVisualVM or Jconsole.exe does? – Bookworm

I assume JConsole et al just use regular JMX access via TCP port; and JVM itself exposes many JMX attributes. – Cristencristi