[PATCH v2 3/4] perf diff: Add diff.compute config option

[Namhyung Kim <namhyung@kernel.org>]

The diff.compute config variable is to set the default compute method of
perf diff command (-c option).  Possible values 'delta' (default),
'delta-abs', 'ratio' and 'wdiff'.

Cc: Taeung Song <treeze.taeung@gmail.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/Documentation/perf-config.txt |  5 +++++
 tools/perf/Documentation/perf-diff.txt   |  5 +++--
 tools/perf/builtin-diff.c                | 16 +++++++++++++++-
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt
index 5b54d47ef713..f2d758dc1edc 100644
--- a/tools/perf/Documentation/perf-config.txt
+++ b/tools/perf/Documentation/perf-config.txt
@@ -505,6 +505,11 @@ Variables
 		Setting it to 1 will sort the result by delta (or other
 		compute method selected).
 
+	diff.compute::
+		This options sets the method of computing diff result.
+		Possible values are 'delta', 'delta-abs', 'ratio' and
+		'wdiff'.  Default is 'delta'.
+
 SEE ALSO
 --------
 linkperf:perf[1]
diff --git a/tools/perf/Documentation/perf-diff.txt b/tools/perf/Documentation/perf-diff.txt
index 6ba3bf582d79..70f490408262 100644
--- a/tools/perf/Documentation/perf-diff.txt
+++ b/tools/perf/Documentation/perf-diff.txt
@@ -86,8 +86,9 @@ OPTIONS
 
 -c::
 --compute::
-        Differential computation selection - delta,ratio,wdiff,delta-abs (default is delta).
-        See COMPARISON METHODS section for more info.
+        Differential computation selection - delta,ratio,wdiff,delta-abs
+	(default is delta).  Default can be changed using diff.compute
+	config option.  See COMPARISON METHODS section for more info.
 
 -p::
 --period::
diff --git a/tools/perf/builtin-diff.c b/tools/perf/builtin-diff.c
index 181ff996e039..4b4004d41c6a 100644
--- a/tools/perf/builtin-diff.c
+++ b/tools/perf/builtin-diff.c
@@ -86,7 +86,7 @@ const char *compute_names[COMPUTE_MAX] = {
 	[COMPUTE_WEIGHTED_DIFF] = "wdiff",
 };
 
-static int compute;
+static int compute = COMPUTE_DELTA;
 
 static int compute_2_hpp[COMPUTE_MAX] = {
 	[COMPUTE_DELTA]		= PERF_HPP_DIFF__DELTA,
@@ -1299,6 +1299,20 @@ static int diff__config(const char *var, const char *value,
 		sort_compute = perf_config_int(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "diff.compute")) {
+		if (!strcmp(value, "delta"))
+			compute = COMPUTE_DELTA;
+		else if (!strcmp(value, "delta-abs"))
+			compute = COMPUTE_DELTA_ABS;
+		else if (!strcmp(value, "ratio"))
+			compute = COMPUTE_RATIO;
+		else if (!strcmp(value, "wdiff"))
+			compute = COMPUTE_WEIGHTED_DIFF;
+		else {
+			pr_err("Invalid compute method: %s\n", value);
+			return -1;
+		}
+	}
 
 	return 0;
 }
-- 
2.11.0