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<p>Seekwatcher generates graphs from blktrace runs to help visualize IO
patterns and performance. It can plot multiple blktrace runs together,
making it easy to compare the differences between different benchmark runs.</p>
<a href=>Ext3 creating 20 copies of the Linux kernel sources</a><p>
<a href=>Ext3 vs XFS creating 20 copies of the Linux kernel sources</a><p>
<p>Seekwatcher uses <a href=>matplotlib</a>
to generate graphs, and most distros have a package for this. You'll also need
to install python and the numpy module. It is common for the matplotlib
packages to depend on numpy, so installing a distro's matplotlib should get you
what you need.<p>
<p>seekwatcher --movie uses mencoder to create mpg files, but it also
leaves around all the .pngs so you can use your own favorite program.</p>
<p>Once those are setup, just copy the seekwatcher script to a bin directory
and make it executable.</p>
<h3>Running Seekwatcher</h3>
<p>There are three basic ways to run seekwatcher. It can either generate
graphs from an existing blktrace run, start blktrace and run a program for
you, or make a series of pngs from a single trace. If seekwatcher starts and
stops blktrace, the trace runs are kept so they can be graphed again later.</p>
<p>This will start blktrace on /dev/sda6, run find / > /dev/null, save the
blktrace output to find.trace and save the graph to find.png.
seekwatcher -t find.trace -o find.png -p 'find / > /dev/null' -d /dev/sda6
<p>To regenerate the graph from the saved trace file:<p>
<pre>seekwatcher -t find.trace -o find.png</pre>
<p>To compare multiple traces, use the -t flag multiple times. Providing a
corresponding -l flag for each trace will create labels on the graphs.<p>
seekwatcher -t ext3.trace -t xfs.trace -l ext3 -l xfs -o ext3_vs_xfs.png
<p>Finally, you can also make a series of images (and mpg) of the IO generated
by a given run. For these images, a disk is simulated as a grid of x,y
coordinates and every sector read/written is plotted with a black square.
Squares fade as the IO ages, blanking out after 10 frames.</p>
<p>To create an animation from ext3.trace and store the resulting png
files in some_dir/ext3-00000N.png (N is replaced by the frame number).
mencoder is run to create some_dir/ext3.mpg based on the images:</p>
seekwatcher -t ext3.trace -o some_dir/ext3.png --movie
<p>Seekwatcher creates 3 graphs by default: a plot of each sector read
or written, the number of seeks per second, and the throughput per second
during the run. Sometimes the plot of each sector can be difficult to read,
especially when comparing two runs with very different IO patterns.
<b>seekwatcher --no-io-graph</b> will disable this plot. Another option
is to use <b>seekwatcher --zoom start:end</b> to specify the range on the yaxis
you want included in the graph. The range is specified in MB, and using
a range of 0:0 will turn off seekwatcher's attempt at autoscaling the plot.</p>
seekwatcher -t ext3.trace -z 10000:20000 -o ext3.png
seekwatcher -t ext3.trace -z 0:0 -o ext3-no-zoom.png
<p>You can change the plot type used in the IO graph with --io-graph-dots.
Matplotlib gives a <a href=>long list of choices</a>. You might try '-' (solid line) or
',' (pixels):<p>
seekwatcher -t ext3.trace --io-graph-dots=,
<p>Seekwatcher uses a rolling average of the seek counts and throughput
values to make graphs smoother. You can control the number of seconds
rolled together (by default total trace time / 25) with
<b>seekwatcher --rolling-avg</b></p>
<h3>Controlling Output</h3>
<p>By default, seekwatcher saves the graph into a file called trace.png.
seekwatcher -o filename can be used to save it to a different file. The
extension specified controls what type of file is created, choices include
.png, .jpg, .eps, and .svg. The resolution used can be controlled with
--dpi num. By default, seekwatcher uses a 8x6 pagesize and a dpi of 120.</p>
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