Stefan Hajnoczi writes: > On Mon, Feb 17, 2014 at 08:36:19PM +0100, Lluís Vilanova wrote: >> Minimizes the amount of backend code, making it simpler to add new/different >> backends. >> >> Also performs other cleanups all around. >> >> Signed-off-by: Lluís Vilanova <vilan...@ac.upc.edu> >> --- >> >> Lluís Vilanova (4): >> trace: [tracetool] Add method 'Event.api' to build event names >> trace: [tracetool,trivial] Style changes >> trace: [tracetool] Identify formats directly used by QEMU >> trace: [tracetool] Minimize the amount of per-backend code
> I think we stretched the concepts of backends and formats too far. > There are formats that only work with one backend (like 'stap'). And > there are backends that behave differently from all other backends. > As a result we're trying to abstract and make common a bunch of stuff > that isn't really common. This problem existed before this patch > series, but I feel we're going further down a direction that > increasingly seems to be wrong. > It's simpler if we turn the design inside-out. Instead of making > backends export all sorts of interfaces and flags, tracetool should just > parse trace-events and hand the list over to the backend. > Let the backend do whatever it wants. The format option simply becomes > an option telling the backend which type of output to generate > (events.h, events.c, .stp, etc). > Common behavior should live in plain old Python modules/functions. > TL;DR moving to a library design would simplify and clean up more than > trying to improve the current framework design > What do you think? This series moves into that direction; some of the formats are simply not handled by backends. For example, the "stap", "events_c" and "events_h" formats have no backend-specific contents. Also, having common code for the "format", and then relying on backends for a small piece of the contents simplifies later patches like the multi-backend tracing. The thing here is that maybe we should change format to "file", since it actually refers to a specific output file. Thanks, Lluis -- "And it's much the same thing with knowledge, for whenever you learn something new, the whole world becomes that much richer." -- The Princess of Pure Reason, as told by Norton Juster in The Phantom Tollbooth
