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+<h3>operf issues on older kernels</h3>
+<p>
+The <tt>operf</tt> tool depends on a kernel feature called Linux Kernel Performance Events Subsystem
+(aka "perf_events").  This feature was initially included with the 2.6.31 kernel, but over the next
+several versions, it evolved rapidly to fix bugs and add new capabilities.  Several Linux distributions
+were released using kernels based on 2.6.31 or 2.6.32 which were heavily patched with perf_events
+fixes.  However, not all critical fixes made their way into these early perf_events-enabled
+Linux distributions.  For example, the <tt>operf</tt> tool from the official 0.9.8 release is
+completely broken when used on SLES 11 SP1, where the following error message occurs:
+<div class="computeroutput">Unexpected error running operf: Permission denied
+Please use the opcontrol command instead of operf.
+</div>
+A fix for this error is available upstream and will be available in 0.9.9.  But the following
+permanent restriction is in place when running on such older kernels:<br>
+when running on such older kernels:<br>
+<blockquote><em>When running <tt>operf</tt> as the root user using the syntax <tt>operf &lt;command&gt;</tt>,
+the profiling phase seems to succeed, but opreport shows no samples collected. The workaround is to use a non-root
+user account for profiling a single application, and use the root user account only for <tt>--system-wide</tt> profiling.
+</em></blockquote>
+</p>
+
+
 
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