Monday 26 October 2009

blktrace based tools - seekwatcher

Previously I blogged about blktrace and how it can be used to analyse block I/O operations - however, it can generate a lot of data that can be overwhelming. This is where Chris Mason's Seekwatcher tool comes to the rescue. Seekwatcher uses blktrace data to generate graphs to help one visualise and understand I/O patterns. It allows one to plot multiple blktrace runs together to enable easy comparison between benchmarking test runs.

It requires matplotlib, python and the numpy module - on Ubuntu download and install these packages using:

sudo apt-get install python python-matplotlib python-numpy

and then get the seekwatcher source and extract seekwatcher from the source package and you are ready to run the seekwatcher python script.

Seekwatcher also can general animations of I/O patterns which also improves visualisation and understanding of I/O operations over time.

To use seekwacher, first start a blktrace capture:

blktrace -o trace -d /dev/sda

next kick off the test you want to analyse and when that's complete, kill blktrace. Next run seekwatcher on the blktrace output:

seekwatcher -t trace.blktrace -o output.png

..and this generates a png file output.png. Easy!

Attached is the output from a test I just ran on my HP Mini 1000 starting up the Open Office word processor:

One can generate a movie from the same data using:

seekwatcher -t trace.blktrace -o open-office.mpg --movie

The generated movie is below:

There are more instructions on other ways to use seekwatcher on the seekwatcher webpage. All in all, a very handy tool - kudos to Chris Mason.


  1. Thanks for posting this, I've been wondering how to analyse I/O for a while.

  2. Thanks for posting it. It helps a lot.