perf stat: Add --log-fd <N> option to redirect stderr elsewhere

This perf stat option emulates valgrind's --log-fd option, allowing the
user to send perf results elsewhere, and leaving stderr for use by the
program under test.  This complements --output file option, and is
mutually exclusive with it.

   3>results  perf stat --log-fd 3          -- $cmd
   3>>results perf stat --log-fd 3 --append -- $cmd

The perl distro's make test.valgrind target uses valgrind's --log-fd
option, I've adapted it to invoke perf also, and tested this patch
there.

Link: http://lkml.kernel.org/r/1315437244-3788-2-git-send-email-jim.cromie@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index bec64a9e741c..a43c68051078 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -196,6 +196,7 @@ static bool			csv_output			= false;
 static bool                     group                           = false;
 static const char               *output_name                    = NULL;
 static FILE                     *output                         = NULL;
+static int                      output_fd;
 
 static volatile int done = 0;
 
@@ -1080,6 +1081,8 @@ static const struct option options[] = {
         OPT_STRING('o', "output", &output_name, "file",
                     "output file name"),
         OPT_BOOLEAN(0, "append", &append_file, "append to the output file"),
+        OPT_INTEGER(0, "log-fd", &output_fd,
+                    "log output to fd, instead of stderr"),
         OPT_END()
 };
 
@@ -1166,6 +1169,10 @@ int cmd_stat(int argc, const char **argv, const char *prefix __used)
         if (output_name && strcmp(output_name, "-"))
                 output = NULL;
 
+        if (output_name && output_fd) {
+                fprintf(stderr, "cannot use both --output and --log-fd\n");
+                usage_with_options(stat_usage, options);
+        }
         if (!output) {
                 struct timespec tm;
                 mode = append_file ? "a" : "w";
@@ -1177,6 +1184,13 @@ int cmd_stat(int argc, const char **argv, const char *prefix __used)
                 }
                 clock_gettime(CLOCK_REALTIME, &tm);
                 fprintf(output, "# started on %s\n", ctime(&tm.tv_sec));
+        } else if (output_fd != 2) {
+                mode = append_file ? "a" : "w";
+                output = fdopen(output_fd, mode);
+                if (!output) {
+                        perror("Failed opening logfd");
+                        return -errno;
+                }
         }
 
         if (csv_sep)