perf trace: Write to stderr by default

Without this patch, it is cumbersome to read the trace output but
ignoring the normal, potentially verbose, output of the debuggee.  One
common example is doing something like the following:

 perf trace -s find /tmp > /dev/null

Without this patch, the trace summary will be lost. Now, it will still
be printed at the end. This behavior is also applied by strace.

Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: David Ahern <dsahern@gmail.com>
Link: http://lkml.kernel.org/n/tip-tqnks6y2cnvm5f9g2dsfr7zl@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 98d423efdaa9bba77afb08989c0eb8a553caeeae..a47497011c93e7ad305d6c0891562e2c6e4aa386 100644 (file)
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -2965,7 +2965,7 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
                        .mmap_pages    = UINT_MAX,
                        .proc_map_timeout  = 500,
                },
-               .output = stdout,
+               .output = stderr,
                .show_comm = true,
                .trace_syscalls = true,
        };