* Adrian Hunter <[email protected]> wrote: > > And I also raised why this shouldn't be the default event tracing > > method instead of a weird config option. Per-cpu tracing is cache > > compact, it is easier to size properly and in general it is pretty > > easy to think about. (It also has less of the TSC timestamp > > ordering problems as per thread tracing, at least in theory.) > > > > Is there something that makes per cpu tracing undesirable as the > > default? > > One reason is to avoid changing the meaning of existing options.
Well, the way the tracing buffers are set up is a mostly tool internal matter so in that sense it should be just fine to change the default behavior - as long as output remains unchanged (which it should). Or is there any material change in behavior somewhere? > To flip it around, ignore the patches above and apply: > Subject: [PATCH] perf record: Make per-cpu mmaps the default. Yay! > +--per-thread:: > +Use per-thread mmaps. By default per-cpu mmaps are created. This option > +overrides that and uses per-thread mmaps. A side-effect of that is that > +inheritance is automatically disabled. --per-thread is ignored with a > warning > +if combined with -a or -C options. I think this is the natural thing to do, --per-thread is the 'somewhat weird' option that cannot be used in all modes. Acked-by: Ingo Molnar <[email protected]> :-) Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
