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

[Namhyung Kim]

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.tae...@gmail.com>
Signed-off-by: Namhyung Kim <namhy...@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