perf diff: Add --percentage option

The --percentage option is for controlling overhead percentage
displayed.  It can only receive either of "relative" or "absolute" and
affects -c delta output only.

For more information, please see previous commit same thing done to
"perf report".

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1397145720-8063-5-git-send-email-namhyung@kernel.org
Signed-off-by: Jiri Olsa <jolsa@redhat.com>

1 files changed, 18 insertions, 3 deletions

diff --git a/tools/perf/Documentation/perf-diff.txt b/tools/perf/Documentation/perf-diff.txt
index fdfceee0ffd0..fbfa1192923c 100644
--- a/tools/perf/Documentation/perf-diff.txt
+++ b/tools/perf/Documentation/perf-diff.txt
@@ -33,17 +33,20 @@ OPTIONS
 -d::
 --dsos=::
         Only consider symbols in these dsos. CSV that understands
-        file://filename entries.
+        file://filename entries.  This option will affect the percentage
+        of the Baseline/Delta column.  See --percentage for more info.
 
 -C::
 --comms=::
         Only consider symbols in these comms. CSV that understands
-        file://filename entries.
+        file://filename entries.  This option will affect the percentage
+        of the Baseline/Delta column.  See --percentage for more info.
 
 -S::
 --symbols=::
         Only consider these symbols. CSV that understands
-        file://filename entries.
+        file://filename entries.  This option will affect the percentage
+        of the Baseline/Delta column.  See --percentage for more info.
 
 -s::
 --sort=::
@@ -89,6 +92,14 @@ OPTIONS
 --order::
        Specify compute sorting column number.
 
+--percentage::
+        Determine how to display the overhead percentage of filtered entries.
+        Filters can be applied by --comms, --dsos and/or --symbols options.
+
+        "relative" means it's relative to filtered entries only so that the
+        sum of shown entries will be always 100%.  "absolute" means it retains
+        the original value before and after the filter is applied.
+
 COMPARISON
 ----------
 The comparison is governed by the baseline file. The baseline perf.data
@@ -157,6 +168,10 @@ with:
   - period_percent being the % of the hist entry period value within
     single data file
 
+  - with filtering by -C, -d and/or -S, period_percent might be changed
+    relative to how entries are filtered.  Use --percentage=absolute to
+    prevent such fluctuation.
+
 ratio
 ~~~~~
 If specified the 'Ratio' column is displayed with value 'r' computed as: