On Fri, Sep 02, 2016 at 05:24:04PM -0400, Stefan Hajnoczi wrote: > On Thu, Aug 11, 2016 at 12:11:06PM +0200, Lluís Vilanova wrote: > > Daniel P Berrange writes: > > > > > On Wed, Aug 10, 2016 at 06:11:24PM +0200, Lluís Vilanova wrote: > > >> Daniel P Berrange writes: > > >> > > >> > On Wed, Aug 10, 2016 at 04:33:47PM +0200, Lluís Vilanova wrote: > > >> >> Daniel P Berrange writes: > > [...] > > >> >> For example, first we concatenate /trace-events, /io/trace-events and > > >> >> /hw/usb/trace-events into /trace-events-all to produce: > > >> >> > > >> >> @group core > > >> >> @dir / > > >> >> # contents of /trace-events > > >> >> @group io > > >> >> @dir /io > > >> >> # contents of /io/trace-events > > >> >> @group hw_usb > > >> >> @dir /hw/usb > > >> >> # contents of /hw/usb/trace-events > > >> >> > > >> >> Then we can use /trace-events-all to generate all the per-directory > > >> >> trace.h > > >> >> files while ensuring a perfectly flat event identifier space (a single > > >> >> generated-events.c is used). > > >> >> > > >> >> This should minimize changes to tracing code and avoid further > > >> >> restrictions > > >> >> (like the "top-level vcpu" one). > > >> > > >> > That means when any individual trace file is changed, we re-generate > > >> > the > > >> > world, which is exactly what this series is designed to avoid. > > >> > > >> Nope. We re-generate /trace-events-all, but each individual file > > >> generated > > >> afterwards (taken from the "@dir" directive) will change only if its new > > >> contents do (the Makefile uses cmp to check if files need updating from > > >> their > > >> corresponding timestamp file). > > > > > The contents will still need to change too if we have a global numbering > > > space as your suggestion requires. The event groups are the only way to > > > avoid that. > > > > Aha, that's true. I didn't think of that, sorry. > > Nevertheless, I agree that @id_offset() should be eliminated to avoid > collisions and manual effort when trace-events files are added.
I think I have a workable solution to eliminate this. During build I'll create a file 'trace-event-file-list' which contains a list of paths to 'trace-event' files in the tree. We'll then use the line number in this file as the id offset for events. The generated $SUBDIR/trace.h file will depend on trace-event-file-list. So we'll have fully automatic numbering for each trace-event file and will only get a full rebuild if someone adds a completely new trace-event file, which is acceptable. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
