Monitor memory and CPU usage on an IU research computing system

• Overview
• Preparing a shell script
• Options
• Plotting output
• Getting help

Overview

The collectl utility is a system-monitoring tool that records specific operating system data for one or more sets of subsystems. Any set of subsystems (for example, CPU, disks, memory, or processes) can be included in or excluded from data collection. Data can be stored in compressed or uncompressed data files, which themselves can be in either raw format or in a space-delineated format that enables plotting using gnuplot or Microsoft Excel.

At Indiana University, you can use collectl to monitor the memory and CPU usage of single-node batch jobs running on Carbonate or Karst, or in the Cluster Compatibility Mode (CCM) execution environment on Big Red II.

Output from collectl can help you determine how many serial applications you can run on a single node. For example, on Big Red II, if collectl output shows that a single serial application consumes about 8 GB of memory and uses a single core, you can stack three of them onto one compute node to optimize the efficient use of that node; see Use PCP to bundle multiple serial jobs to run in parallel on Big Red II at IU

Likewise, on Carbonate or Karst, you can use collectl output to help determine the resources you need to request to run your batch job.

Preparing a shell script

The collectl utility runs a lightweight application alongside your binary, capturing its memory and CPU usage as it runs on a compute node.

A simple way to launch collectl alongside your binary is to prepare a simple shell script, which you can later submit to TORQUE using a job script.

For example, consider the following shell script (my_script.sh) for launching the binary ./my_binary:

  #!/bin/bash cd /N/dc2/scratch/username/temp ./my_binary

To have collectl record subsystem data as your binary runs, add lines to the shell script for loading the collectl module, including data collection instructions, and stopping data collection after your binary has finished running. For example, after applying such changes, the my_script.sh shell script would look similar to this:

  #!/bin/bash module load collectl cd /N/dc2/scratch/username/temp SAMPLEINTERVAL=10 COLLECTLDIRECTORY=/N/dc2/scratch/username/temp/ collectl -F1 -i$SAMPLEINTERVAL:$SAMPLEINTERVAL -sZl --procfilt u$UID -f $COLLECTLDIRECTORY & ./my_binary collectl_stop.sh

In the above example:

• Adjust SAMPLEINTERVAL according to the expected runtime for your application. If your job will run for less than a day, UITS recommends setting SAMPLEINTERVAL=10; if your job will run for multiple days, set SAMPLEINTERVAL=30 or SAMPLEINTERVAL=60.
• To point COLLECTLDIRECTORY to your Data Capacitor II scratch space, replace username with your IU username.
• The & at the end of the collectl command places the collectl process in the background, allowing your script to issue other commands (for example, ./my_binary) while collectl runs and collects data.
• The collectl_stop.sh command kills the collectl process, stopping data collection.

Options

Following is a summary of commonly used collectl options; for a complete list, load the collectl module, and then refer to the collectl manual page (man collectl):

Plotting output

After your job has run to completion, collectl will place an output file (for example, nid00862-20130826-130847.raw.gz) in the directory specified by COLLECTLDIRECTORY. You then can use the collectl_plot.sh shell script to create a chart depicting the runtime characteristics of your application.

For example:

  collectl_plot.sh output_file .

In the above example, replace output_file with the name of the collectl output file (for example, nid00862-20130826-130847.raw.gz). Remember to include the period (.) at the end of the line.

Running collectl_plot.sh will create a collectl_plot_tmp subdirectory off the current directory that will contain the files used to create the plots, which will appear in your current directory as .eps files.

The default charts produced after running collectl_plot.sh are:

You can view these files using any graphics program that can read .eps files (for example, Acrobat, Apple Preview, Ghostview, Illustrator, and Photoshop, among others). Alternatively, you can drag them into an open Microsoft Word document, or use Word's Insert Picture from File function.

If your application does not run long enough to generate multiple data points, collectl_plot.sh may create empty files. In such cases, collectl_plot.sh may generate messages indicating it encountered errors while parsing the data.

On Big Red II, if your plots for I/O data (for example, io.eps and io_sum.eps) are empty, most likely the I/O of the process is not being recorded. However, some file system I/O may be recorded in the collectl output (raw.gz) file. To find this I/O data within the collectl output file, search for lines containing read_bytes or write_bytes.

Getting help

For more, see the collectl manual page (man collectl) or visit the Collectl project page.

If you need help or have questions about using collectl, contact the Scientific Applications and Performance Tuning team.