Add performance section

raster/r.univar/r.univar.html

@@ -48,6 +48,26 @@ <h2>NOTES</h2>
 map and uploads statistics to new attribute columns, see
 <em><a href="v.rast.stats.html">v.rast.stats</a></em>.
 
+<h2>PERFORMANCE</h2>
+
+<p>
+<em>r.univar</em> has received OpenMP support for parallel processing. The user 
+can specify the number of threads to be used with the <b>nprocs</b> parameter.
+However, parallelization is disabled when the <b>-e</b> extended statistics
+flag is used.
+
+<p>
+Due to the differences in summation order, users may encounter floating points
+discrepancies when <em>r.univar</em> is run on larger raster files when different
+<b>nprocs</b> parameters are used. However, since the work allocation among threads
+is static, users should expect to have the same results when run with the same 
+number of threads.
+
+<p>
+Users should expect to observe close to n-fold speedup for n-fold processors on 
+reasonably large raster map. The speedup is however limited depending on the number 
+of cores available in the users' hardware.
+
 <h2>EXAMPLES</h2>
 
 <h3>Univariate statistics</h3>