Fix unit

doc/chapters/perf-feedback.texi

@@ -340,7 +340,7 @@ file: <starpu_slu_lu_model_12.hannibal>
 @end example
 
 Here, the codelets of the lu example are available. We can examine the
-performance of the 22 kernel (in ms):
+performance of the 22 kernel (in micro-seconds):
 
 @example
 $ starpu_perfmodel_display -s starpu_slu_lu_model_22

doc/chapters/perf-optimization.texi

@@ -158,7 +158,7 @@ b50b6605  393216   1.469926e+03  1.088828e+02  1240
 @end example
 
 Which shows that for the LU 22 kernel with a 1.5MiB matrix, the average
-execution time on CPUs was about 12ms, with a 2ms standard deviation, over
+execution time on CPUs was about 11ms, with a 3ms standard deviation, over
 1240 samples. It is a good idea to check this before doing actual performance
 measurements.