perf intel-pt: Update documentation about itrace G and L options
Provide a little more information about the new G and L options,
particularly the issue with large PEBs.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/20200429150751.12570-9-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/Documentation/itrace.txt b/tools/perf/Documentation/itrace.txt
index 0326050..2714847 100644
--- a/tools/perf/Documentation/itrace.txt
+++ b/tools/perf/Documentation/itrace.txt
@@ -33,6 +33,10 @@
Also the number of last branch entries (default 64, max. 1024) for
instructions or transactions events can be specified.
+ Similar to options g and l, size may also be specified for options G and L.
+ On x86, note that G and L work poorly when data has been recorded with
+ large PEBS. Refer linkperf:perf-intel-pt[1] man page for details.
+
It is also possible to skip events generated (instructions, branches, transactions,
ptwrite, power) at the beginning. This is useful to ignore initialization code.