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SubjectRe: [RFC][PATCH 0/9] perf trace: support for general-purpose scripting
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On Tue, 2009-10-06 at 11:09 +0200, Ingo Molnar wrote:
> * Tom Zanussi <tzanussi@gmail.com> wrote:
>
> > Known problems/shortcomings:
> >
> > Probably the biggest problem right now is the sorting hack I added as
> > the last patch. It's just meant as a temporary thing, but is there
> > because tracing scripts in general want to see events in the order
> > they happened i.e. timestamp order. [...]
>
> Btw., have you seen the -M/--multiplex option to perf record? It
> multiplexes all events into a single buffer - making them all ordered.
> (The events are in causal ordering in this case even if there's some TSC
> asynchronity)

It also wrecks large machines.. I've been thinking about limiting the
number of CPUs you can redirect into a single output stream using the
output_fd thing, but then the inherited stuff makes that very hard.

And we also need a solution for the inhertited counters, the best would
be the per-cpu inherited things, where we use both cpu and pid, instead
of either.

In short, -M is nice, but it also has significant down sides, esp. with
machines getting more and more cores.



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