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-rw-r--r--tools/perf/Documentation/perf-diff.txt5
-rw-r--r--tools/perf/util/sort.c9
2 files changed, 14 insertions, 0 deletions
diff --git a/tools/perf/Documentation/perf-diff.txt b/tools/perf/Documentation/perf-diff.txt
index e463caa3eb49..518266192d67 100644
--- a/tools/perf/Documentation/perf-diff.txt
+++ b/tools/perf/Documentation/perf-diff.txt
@@ -20,6 +20,11 @@ If no parameters are passed it will assume perf.data.old and perf.data.
The differential profile is displayed only for events matching both
specified perf.data files.
+If no parameters are passed the samples will be sorted by dso and symbol.
+As the perf.data files could come from different binaries, the symbols addresses
+could vary. So perf diff is based on the comparison of the files and
+symbols name.
+
OPTIONS
-------
-D::
diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
index 7a39c1ed8d37..4593f36ecc4c 100644
--- a/tools/perf/util/sort.c
+++ b/tools/perf/util/sort.c
@@ -1463,6 +1463,15 @@ int sort_dimension__add(const char *tok)
sort__has_parent = 1;
} else if (sd->entry == &sort_sym) {
sort__has_sym = 1;
+ /*
+ * perf diff displays the performance difference amongst
+ * two or more perf.data files. Those files could come
+ * from different binaries. So we should not compare
+ * their ips, but the name of symbol.
+ */
+ if (sort__mode == SORT_MODE__DIFF)
+ sd->entry->se_collapse = sort__sym_sort;
+
} else if (sd->entry == &sort_dso) {
sort__has_dso = 1;
}