perf report: Allow configuring the default sort order in ~/.perfconfig

Allows changing the default sort order from "comm,dso,symbol" to some
other default, for instance "sym,dso" may be more fitting for kernel
developers.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-pm1h5puxua8nsxksd68fjm8r@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt
index 15949e2..68c8919 100644
--- a/tools/perf/Documentation/perf-config.txt
+++ b/tools/perf/Documentation/perf-config.txt
@@ -382,6 +382,10 @@
 		histogram entry. Default is 0 which means no limitation.
 
 report.*::
+	report.sort_order::
+		Allows changing the default sort order from "comm,dso,symbol" to
+		some other default, for instance "sym,dso" may be more fitting for
+		kernel developers.
 	report.percent-limit::
 		This one is mostly the same as call-graph.threshold but works for
 		histogram entries. Entries having an overhead lower than this