Add note about OpenMPI locked memory limit failure

doc/html/mpi_guide.shtml

@@ -98,7 +98,6 @@ $ salloc -n4 sh   # allocates 4 processors and spawns shell for job
 > srun --mpi=pmi2 -n 4 a.out
 </pre>
 
-
 <p>If the ports reserved for a job step are found by the Open MPI library
 to be in use, a message of this form will be printed and the job step
 will be re-launched:<br>
@@ -108,6 +107,12 @@ Repeated failures should be reported to your system administrator in
 order to rectify the problem by cancelling the processes holding those
 ports.</p>
 
+<p>NOTE: Some kernels and system configurations have resulted in a locked memory
+too small for proper OpemMPI functionality, resulting in application failure
+with a segmentation fault. This may be fixed by configuring the slurmd daemon
+to execute with a larger limit. For example, add "LimitMEMLOCK=infinity" to
+your slurmd.service file.</p>
+
 <hr size=4 width="100%">
 
 <h2><a name="intel_mpi"><b>Intel MPI</b></a></h2>
@@ -512,6 +517,6 @@ $ srun -N4 -n16 a.out
 
 <hr size=4 width="100%">
 
-<p style="text-align:center;">Last modified 20 April 2015</p>
+<p style="text-align:center;">Last modified 23 June 2015</p>
 
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