<link>http://people.skolelinux.org/pere/blog/</link>
<atom:link href="http://people.skolelinux.org/pere/blog/index.rss" rel="self" type="application/rss+xml" />
+ <item>
+ <title>Coz can help you find bottlenecks in multi-threaded software - nice free software</title>
+ <link>http://people.skolelinux.org/pere/blog/Coz_can_help_you_find_bottlenecks_in_multi_threaded_software___nice_free_software.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Coz_can_help_you_find_bottlenecks_in_multi_threaded_software___nice_free_software.html</guid>
+ <pubDate>Thu, 11 Aug 2016 12:00:00 +0200</pubDate>
+ <description><p>This summer, I read a great article
+"<a href="https://www.usenix.org/publications/login/summer2016/curtsinger">coz:
+This Is the Profiler You're Looking For</a>" 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.</p>
+
+<p>The project and presentation was so inspiring that I would like to
+get the system into Debian. I
+<a href="https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=830708">created
+a WNPP request for it</a> 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.</p>
+
+<p>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:
+
+<p><blockquote><pre>
+coz run --- program-to-run
+</pre></blockquote></p>
+
+<p>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
+<a href="http://plasma-umass.github.io/coz/">http://plasma-umass.github.io/coz/</a>
+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 &lt;coz.h&gt; 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.</p>
+
+<p>A video published by ACM
+<a href="https://www.youtube.com/watch?v=jE0V-p1odPg">presenting the
+Coz profiler</a> is available from Youtube. There is also a paper
+from the 25th Symposium on Operating Systems Principles available
+titled
+<a href="https://www.usenix.org/conference/atc16/technical-sessions/presentation/curtsinger">Coz:
+finding code that counts with causal profiling</a>.</p>
+
+<p><a href="https://github.com/plasma-umass/coz">The source code</a>
+for Coz is available from github. It will only build with clang
+because it uses a
+<a href="https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55606">C++
+feature missing in GCC</a>, but I've submitted
+<a href="https://github.com/plasma-umass/coz/pull/67">a patch to solve
+it</a> and hope it will be included in the upstream source soon.</p>
+
+<p>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.</p>
+</description>
+ </item>
+
<item>
<title>Sales number for the Free Culture translation, first half of 2016</title>
<link>http://people.skolelinux.org/pere/blog/Sales_number_for_the_Free_Culture_translation__first_half_of_2016.html</link>
</description>
</item>
- <item>
- <title>Discharge rate estimate in new battery statistics collector for Debian</title>
- <link>http://people.skolelinux.org/pere/blog/Discharge_rate_estimate_in_new_battery_statistics_collector_for_Debian.html</link>
- <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Discharge_rate_estimate_in_new_battery_statistics_collector_for_Debian.html</guid>
- <pubDate>Mon, 23 May 2016 09:35:00 +0200</pubDate>
- <description><p>Yesterday I updated the
-<a href="https://tracker.debian.org/pkg/battery-stats">battery-stats
-package in Debian</a> with a few patches sent to me by skilled and
-enterprising users. There were some nice user and visible changes.
-First of all, both desktop menu entries now work. A design flaw in
-one of the script made the history graph fail to show up (its PNG was
-dumped in ~/.xsession-errors) if no controlling TTY was available.
-The script worked when called from the command line, but not when
-called from the desktop menu. I changed this to look for a DISPLAY
-variable or a TTY before deciding where to draw the graph, and now the
-graph window pop up as expected.</p>
-
-<p>The next new feature is a discharge rate estimator in one of the
-graphs (the one showing the last few hours). New is also the user of
-colours showing charging in blue and discharge in red. The percentages
-of this graph is relative to last full charge, not battery design
-capacity.</p>
-
-<p align="center"><img src="http://people.skolelinux.org/pere/blog/images/2016-05-23-battery-stats-rate.png"/></p>
-
-<p>The other graph show the entire history of the collected battery
-statistics, comparing it to the design capacity of the battery to
-visualise how the battery life time get shorter over time. The red
-line in this graph is what the previous graph considers 100 percent:
-
-<p align="center"><img src="http://people.skolelinux.org/pere/blog/images/2016-05-23-battery-stats-history.png"/></p>
-
-<p>In this graph you can see that I only charge the battery to 80
-percent of last full capacity, and how the capacity of the battery is
-shrinking. :(</p>
-
-<p>The last new feature is in the collector, which now will handle
-more hardware models. On some hardware, Linux power supply
-information is stored in /sys/class/power_supply/ACAD/, while the
-collector previously only looked in /sys/class/power_supply/AC/. Now
-both are checked to figure if there is power connected to the
-machine.</p>
-
-<p>If you are interested in how your laptop battery is doing, please
-check out the
-<a href="https://tracker.debian.org/pkg/battery-stats">battery-stats</a>
-in Debian unstable, or rebuild it on Jessie to get it working on
-Debian stable. :) The upstream source is available from <a
-href="https://github.com/petterreinholdtsen/battery-stats">github</a>.
-Patches are very welcome.</p>
-
-<p>As usual, if you use Bitcoin and want to show your support of my
-activities, please send Bitcoin donations to my address
-<b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p>
-</description>
- </item>
-
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