Messages in this thread | | | Subject | Re: [RFC][PATCH 0/9] perf trace: support for general-purpose scripting | From | Peter Zijlstra <> | Date | Tue, 06 Oct 2009 15:25:54 +0200 |
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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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