Messages in this thread | | | Date | Fri, 15 Nov 2013 12:10:32 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 10/10] perf record: Add an option to force per-cpu mmaps |
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* Adrian Hunter <adrian.hunter@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?
> 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 <mingo@kernel.org>
:-)
Thanks,
Ingo
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