On Wed, 9 Dec 2020 at 17:42, Stefan Hajnoczi <stefa...@redhat.com> wrote: > > The "simple" backend is actually more complicated to use than the "log" > backend. Update the quickstart documentation to feature the "log" > backend instead of the "simple" backend. > > Suggested-by: Peter Maydell <peter.mayd...@linaro.org> > Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> > --- > docs/devel/tracing.rst | 19 ++++++++----------- > 1 file changed, 8 insertions(+), 11 deletions(-) > > diff --git a/docs/devel/tracing.rst b/docs/devel/tracing.rst > index 76cc1b24fa..039a0bb267 100644 > --- a/docs/devel/tracing.rst > +++ b/docs/devel/tracing.rst > @@ -11,9 +11,9 @@ for debugging, profiling, and observing execution. > Quickstart > ========== > > -1. Build with the 'simple' trace backend:: > +1. Build with the 'log' trace backend:: > > - ./configure --enable-trace-backends=simple > + ./configure --enable-trace-backends=log > make
Isn't this the default ? It seems to me that the real "quickstart" is "your QEMU binary was likely already built with the log backend, so all you need to do is pass it '-trace eventname -trace eventname' or '-trace some-pattern*'" (or whatever the syntax is: I usually use -d trace=something but I assume we'd rather suggest -trace to new users ?) We can suggest also "if you have a lot of events you might find it useful to put them in a file and use --trace events=file" but IME that's not the common case for "getting started with just outputting trace events" because you can usually enable a whole device's trace events with one suitable glob pattern. > 2. Create a file with the events you want to trace:: > @@ -24,10 +24,6 @@ Quickstart > > qemu --trace events=/tmp/events ... # your normal QEMU invocation > > -4. Pretty-print the binary trace file:: > - > - ./scripts/simpletrace.py trace-events-all trace-* # Override * with QEMU > <pid> > - > Trace events > ============ > > @@ -195,7 +191,7 @@ script. > > The trace backends are chosen at configure time:: > > - ./configure --enable-trace-backends=simple > + ./configure --enable-trace-backends=log 'log' is the default so we don't need to specifically suggest people select it as a configure argument. > For a list of supported trace backends, try ./configure --help or see below. > If multiple backends are enabled, the trace is sent to them all. > @@ -227,10 +223,11 @@ uses DPRINTF(). > Simpletrace > ----------- > > -The "simple" backend supports common use cases and comes as part of the QEMU > -source tree. It may not be as powerful as platform-specific or third-party > -trace backends but it is portable. This is the recommended trace backend > -unless you have specific needs for more advanced backends. > +The "simple" backend writes binary trace logs to a file from a thread, making > +it lower overhead than the "log" backend. A Python API is available for > writing > +offline trace file analysis scripts. It may not be as powerful as > +platform-specific or third-party trace backends but it is portable and has no > +special library dependencies. > > Monitor commands > ~~~~~~~~~~~~~~~~ thanks -- PMM
