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[homepage.git] / blog / archive / 2016 / 08 / 08.rss

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                 <link>http://people.skolelinux.org/pere/blog/</link>
 
        
+       <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>&lt;p&gt;This summer, I read a great article
+&quot;&lt;a href=&quot;https://www.usenix.org/publications/login/summer2016/curtsinger&quot;&gt;coz:
+This Is the Profiler You&#39;re Looking For&lt;/a&gt;&quot; 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 &quot;speeding up&quot; parts of
+the code to various degrees compared to a normal run.  It does this by
+slowing down parallel threads while the &quot;faster up&quot; 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.&lt;/p&gt;
+
+&lt;p&gt;The project and presentation was so inspiring that I would like to
+get the system into Debian.  I
+&lt;a href=&quot;https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=830708&quot;&gt;created
+a WNPP request for it&lt;/a&gt; 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 &#39;git clone&#39; 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.&lt;/p&gt;
+
+&lt;p&gt;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:
+
+&lt;p&gt;&lt;blockquote&gt;&lt;pre&gt;
+coz run --- program-to-run
+&lt;/pre&gt;&lt;/blockquote&gt;&lt;/p&gt;
+
+&lt;p&gt;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
+&lt;a href=&quot;http://plasma-umass.github.io/coz/&quot;&gt;http://plasma-umass.github.io/coz/&lt;/a&gt;
+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 &amp;lt;coz.h&amp;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.&lt;/p&gt;
+
+&lt;p&gt;A video published by ACM
+&lt;a href=&quot;https://www.youtube.com/watch?v=jE0V-p1odPg&quot;&gt;presenting the
+Coz profiler&lt;/a&gt; is available from Youtube.  There is also a paper
+from the 25th Symposium on Operating Systems Principles available
+titled
+&lt;a href=&quot;https://www.usenix.org/conference/atc16/technical-sessions/presentation/curtsinger&quot;&gt;Coz:
+finding code that counts with causal profiling&lt;/a&gt;.&lt;/p&gt;
+
+&lt;p&gt;&lt;a href=&quot;https://github.com/plasma-umass/coz&quot;&gt;The source code&lt;/a&gt;
+for Coz is available from github.  It will only build with clang
+because it uses a
+&lt;a href=&quot;https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55606&quot;&gt;C++
+feature missing in GCC&lt;/a&gt;, but I&#39;ve submitted
+&lt;a href=&quot;https://github.com/plasma-umass/coz/pull/67&quot;&gt;a patch to solve
+it&lt;/a&gt; and hope it will be included in the upstream source soon.&lt;/p&gt;
+
+&lt;p&gt;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.&lt;/p&gt;
+</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>