Re: [PULL 10/11] trace: document how to specify multiple --trace patterns

[Kevin Wolf]

Am 01.02.2021 um 17:29 hat BALATON Zoltan geschrieben:
> On Mon, 1 Feb 2021, Kevin Wolf wrote:
> > Am 01.02.2021 um 17:05 hat BALATON Zoltan geschrieben:
> > > On Mon, 1 Feb 2021, Stefan Hajnoczi wrote:
> > > > It is possible to repeat the --trace option to specify multiple
> > > > patterns. This may be preferrable to users who do not want to create a
> > > > file with a list of patterns.
> > > > 
> > > > Suggested-by: BALATON Zoltan <balaton@eik.bme.hu>
> > > > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > > > Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> > > > Message-id: 20210112165859.225534-2-stefanha@redhat.com
> > > > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > > > ---
> > > > docs/devel/tracing.rst | 9 +++++++--
> > > > 1 file changed, 7 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/docs/devel/tracing.rst b/docs/devel/tracing.rst
> > > > index af395e957d..e8f9b82c5e 100644
> > > > --- a/docs/devel/tracing.rst
> > > > +++ b/docs/devel/tracing.rst
> > > > @@ -22,10 +22,15 @@ events::
> > > > This output comes from the "log" trace backend that is enabled by 
> > > > default when
> > > > ``./configure --enable-trace-backends=BACKENDS`` was not explicitly 
> > > > specified.
> > > > 
> > > > -More than one trace event pattern can be specified by providing a file
> > > > -instead::
> > > > +Multiple patterns can be specified by repeating the ``--trace`` 
> > > > option::
> > > > +
> > > > +    $ qemu --trace "kvm_*" --trace "virtio_*" ...
> > > 
> > > Does that actually work? I've always used -trace enable="pattern1" -trace
> > > enable="pattern2" Not sure if omitting enable= is the same.
> > 
> > qemu_trace_opts has .implied_opt_name = "enable", so without having
> > tested it, I assume this works.
> 
> How does this option parsing work? Would then multiple patterns separated by
> comma as in -trace pattern1,pattern2 also work?

This would be interpreted as an implied "enable" option with a value of
"pattern1,pattern2". I don't think anything splits that string at the
comma, so it would look for a trace event matching that string.

Kevin