[Qemu-devel] [PATCH v2 1/1] Print PID and time in stderr traces

[Qemu-devel] [PATCH v2 1/1] Print PID and time in stderr traces

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

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>
---

v2
  0 pad usec part

 scripts/tracetool/backend/stderr.py | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/scripts/tracetool/backend/stderr.py b/scripts/tracetool/backend/stderr.py
index 2a1e906..ca58054 100644
--- a/scripts/tracetool/backend/stderr.py
+++ b/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,
-- 
2.1.0

Re: [Qemu-devel] [PATCH v2 1/1] Print PID and time in stderr traces

[Dr. David Alan Gilbert]

* Dr. David Alan Gilbert (git) (dgilbert@redhat.com) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> 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>

Ping.

Dave

> ---
> 
> v2
>   0 pad usec part
> 
>  scripts/tracetool/backend/stderr.py | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/tracetool/backend/stderr.py b/scripts/tracetool/backend/stderr.py
> index 2a1e906..ca58054 100644
> --- a/scripts/tracetool/backend/stderr.py
> +++ b/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,
> -- 
> 2.1.0
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH v2 1/1] Print PID and time in stderr traces

[Stefan Hajnoczi]

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On Tue, Jan 20, 2015 at 09:41:15AM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> 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>
> ---
> 
> v2
>   0 pad usec part
> 
>  scripts/tracetool/backend/stderr.py | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)

Thanks, applied to my tracing tree:
https://github.com/stefanha/qemu/commits/tracing

Stefan

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