+
This summer, I read a great article
+"coz:
+This Is the Profiler You're Looking For" in USENIX ;login: about
+how to profile multi-threaded programs. It presented a system for
+profiling software by running experiences in the running program,
+testing how run time performance is affected by "speeding up" parts of
+the code to various degrees compared to a normal run. It does this by
+slowing down parallel threads while the "faster up" code is running
+and measure how this affect processing time. The processing time is
+measured using probes inserted into the code, either using progress
+counters (COZ_PROGRESS) or as latency meters (COZ_BEGIN/COZ_END). It
+can also measure unmodified code by measuring complete the program
+runtime and running the program several times instead.
+
+
The project and presentation was so inspiring that I would like to
+get the system into Debian. I
+created
+a WNPP request for it and contacted upstream to try to make the
+system ready for Debian by sending patches. The build process need to
+be changed a bit to avoid running 'git clone' to get dependencies, and
+to include the JavaScript web page used to visualize the collected
+profiling information included in the source package.
+But I expect that should work out fairly soon.
+
+
The way the system work is fairly simple. To run an coz experiment
+on a binary with debug symbols available, start the program like this:
+
+
+coz run --- program-to-run
+
+
+
This will create a text file profile.coz with the instrumentation
+information. To show what part of the code affect the performance
+most, use a web browser and either point it to
+http://plasma-umass.github.io/coz/
+or use the copy from git (in the gh-pages branch). Check out this web
+site to have a look at several example profiling runs and get an idea what the end result from the profile runs look like. To make the
+profiling more useful you include <coz.h> and insert the
+COZ_PROGRESS or COZ_BEGIN and COZ_END at appropriate places in the
+code, rebuild and run the profiler. This allow coz to do more
+targeted experiments.
+
+
A video published by ACM
+presenting the
+Coz profiler is available from Youtube. There is also a paper
+from the 25th Symposium on Operating Systems Principles available
+titled
+Coz:
+finding code that counts with causal profiling.
+
+
The source code
+for Coz is available from github. It will only build with clang
+because it uses a
+C++
+feature missing in GCC, but I've submitted
+a patch to solve
+it and hope it will be included in the upstream source soon.
+
+
Please get in touch if you, like me, would like to see this piece
+of software in Debian. I would very much like some help with the
+packaging effort, as I lack the in depth knowledge on how to package
+C++ libraries.
+
+