[PULL 08/11] trace: make the 'log' backend timestamp configurable

[Stefan Hajnoczi <stefanha@redhat.com>]

Timestamps in tracing output can be distracting. Make it possible to
control tid/timestamp printing with -msg timestamp=on|off. The default
is no tid/timestamps. Previously they were always printed.

Suggested-by: BALATON Zoltan <balaton@eik.bme.hu>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: BALATON Zoltan <balaton@eik.bme.hu>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20210125113507.224287-3-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 docs/devel/tracing.rst           |  3 +++
 scripts/tracetool/backend/log.py | 19 +++++++++++++------
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/docs/devel/tracing.rst b/docs/devel/tracing.rst
index 4ebf8e38ea..af395e957d 100644
--- a/docs/devel/tracing.rst
+++ b/docs/devel/tracing.rst
@@ -224,6 +224,9 @@ effectively turns trace events into debug printfs.
 This is the simplest backend and can be used together with existing code that
 uses DPRINTF().
 
+The -msg timestamp=on|off command-line option controls whether or not to print
+the tid/timestamp prefix for each trace event.
+
 Simpletrace
 -----------
 
diff --git a/scripts/tracetool/backend/log.py b/scripts/tracetool/backend/log.py
index bc43dbb4f4..17ba1cd90e 100644
--- a/scripts/tracetool/backend/log.py
+++ b/scripts/tracetool/backend/log.py
@@ -20,6 +20,7 @@ PUBLIC = True
 
 def generate_h_begin(events, group):
     out('#include "qemu/log-for-trace.h"',
+        '#include "qemu/error-report.h"',
         '')
 
 
@@ -35,14 +36,20 @@ def generate_h(event, group):
         cond = "trace_event_get_state(%s)" % ("TRACE_" + event.name.upper())
 
     out('    if (%(cond)s && qemu_loglevel_mask(LOG_TRACE)) {',
-        '        struct timeval _now;',
-        '        gettimeofday(&_now, NULL);',
+        '        if (message_with_timestamp) {',
+        '            struct timeval _now;',
+        '            gettimeofday(&_now, NULL);',
         '#line %(event_lineno)d "%(event_filename)s"',
-        '        qemu_log("%%d@%%zu.%%06zu:%(name)s " %(fmt)s "\\n",',
-        '                 qemu_get_thread_id(),',
-        '                 (size_t)_now.tv_sec, (size_t)_now.tv_usec',
-        '                 %(argnames)s);',
+        '            qemu_log("%%d@%%zu.%%06zu:%(name)s " %(fmt)s "\\n",',
+        '                     qemu_get_thread_id(),',
+        '                     (size_t)_now.tv_sec, (size_t)_now.tv_usec',
+        '                     %(argnames)s);',
         '#line %(out_next_lineno)d "%(out_filename)s"',
+        '        } else {',
+        '#line %(event_lineno)d "%(event_filename)s"',
+        '            qemu_log("%(name)s " %(fmt)s "\\n"%(argnames)s);',
+        '#line %(out_next_lineno)d "%(out_filename)s"',
+        '        }',
         '    }',
         cond=cond,
         event_lineno=event.lineno,
-- 
2.29.2