On 15/11/13 13:10, Ingo Molnar wrote: > > * Adrian Hunter <adrian.hun...@intel.com> 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?
Inheritance is enabled automatically with per-cpu mmaps, although that is one of the reasons people want per-cpu mmaps. > >> 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 <mi...@kernel.org> > > :-) > > Thanks, > > Ingo > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
