Collecting native memory information on operating systems other than Windows

To collect memory usage information for a Java™ or Node.js process you must first identify the process you want to monitor, then use an operating system command such as svmon or ps to gather the information.

1. List all the Java or Node.js processes that are running on your machine.
   Use one of the following commands to list all the processes:

   • On AIX:

     ps -e -o "pid args"

   • On Linux:

     ps -e -ww -o "pid args"

   Use one of the following commands to list the processes owned by a specific user:

   • On AIX:

     ps -u userid -o "pid args"

   • On Linux:

     ps -u userid -ww -o "pid args"

   • On z/OS:

     ps -e -o "jobname pid args"

2. Identify the Java or Node.js process that you want to gather memory usage information for, and record its process ID for user later in this task.

   You can identify Java or Node.js processes in the process list by looking for the path to the Java or Node.js program that is running the process. If you are gathering verbose garbage collection data for the process, the output also contains the string -verbose:gc.

3. Modify the following example script to gather memory usage information on your operating system.

   You use a system command to gather memory usage information, however the command produces only a snapshot of information. To plot and analyze memory usage you must have information that covers a period of time. To process the data with GCMV, the information must also include the time when the collection of data began and how frequently the data was gathered. The example script runs the system command at fixed intervals, and generates information that contains the date, a message about the intervals between invocations of the system command, and the output from the system command.

   Find the comments in the script that relate to operating systems and remove the comment and operating system string for the line that is relevant to you. For example if you are using the AIX operating system, change # AIX: echo "svmon interval = $INTERVAL" to echo "svmon interval = $INTERVAL".

   Note: Although the script uses the ps command only for Linux operating systems, you can also use it on AIX systems that support the proc file system. However the svmon command provides more information.

   #!/bin/sh
   
   # The process id to monitor is the first and only argument.
   PID=$1
   # The interval between command invocations, in seconds.
   INTERVAL=3
   
   # Echo the date line to record the start of monitoring.
   # AIX or Linux: echo timestamp = `date +%s`
   # z/OS: echo timestamp = `date`
   
   # Echo the interval frequency.
   # AIX: echo "svmon interval = $INTERVAL"
   # Linux or z/OS: echo "ps interval = $INTERVAL"
   
   # Run the system command at intervals.
   # AIX or Linux: while ([ -d /proc/$PID ]) do
   # z/OS: while true ; do
           # AIX: svmon -r -m -P $PID 
           # Linux: ps -p $PID -o pid,vsz,rss
           # z/OS: ps -p $PID -o pid,vsz
           sleep $INTERVAL
   done

   On the z/OS operating system, some jobs span multiple processes. Use the following script to obtain usage values across all the processes with the same job name.

   #!/bin/sh
   
   # The jobname to monitor is the first and only argument.
   JOBNAME=$1
   # The interval between ps invocations, in seconds.
   INTERVAL=3
   
   # Echo the date line so we know when monitoring began.
   echo timestamp = `date`
   # Echo the interval frequency.
   echo "ps interval = $INTERVAL"
   
   while true ; do
       echo "       PID    VSZ  JOBNAME"
       ps -o pid,vsz,jobname | grep $JOBNAME
       sleep $INTERVAL
   done

4. Run the script, specifying the process ID to monitor or the z/OS job name, and redirect the script output to a file.

   For example, the following command generates an output file called memusage.out, which contains memory usage information for the process whose ID is 1234. The example assumes that the script is saved as a file called memscript.sh, and made executable by using the chmod u+x command.

    ./memscript.sh 1234 > memusage.out 

   If you do not redirect the output, it is written to the standard output (stdout) stream.

timestamp = Fri Jul 16 03:49:21 EDT 2010
ps interval = 3
  PID   VSZ  
 9471 1145580 
  PID   VSZ  
 9471 1145580 
  PID   VSZ 
 9471 1145580 
......