trace: Print PID and time in stderr traces

When debugging migration it's useful to know the PID of
each trace message so you can figure out if it came from the source
or the destination.

Printing the time makes it easy to do latency measurements or timings
between trace points.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: 1421746875-9962-1-git-send-email-dgilbert@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

scripts/tracetool/backend/stderr.py

@@ -21,6 +21,9 @@ PUBLIC = True
 
 def generate_h_begin(events):
     out('#include <stdio.h>',
+        '#include <sys/time.h>',
+        '#include <sys/types.h>',
+        '#include <unistd.h>',
         '#include "trace/control.h"',
         '')
 
@@ -31,7 +34,12 @@ def generate_h(event):
         argnames = ", " + argnames
 
     out('    if (trace_event_get_state(%(event_id)s)) {',
-        '        fprintf(stderr, "%(name)s " %(fmt)s "\\n" %(argnames)s);',
+        '        struct timeval _now;',
+        '        gettimeofday(&_now, NULL);',
+        '        fprintf(stderr, "%%d@%%zd.%%06zd:%(name)s " %(fmt)s "\\n",',
+        '                        getpid(),',
+        '                        (size_t)_now.tv_sec, (size_t)_now.tv_usec',
+        '                        %(argnames)s);',
         '    }',
         event_id="TRACE_" + event.name.upper(),
         name=event.name,