Messages in this thread | | | Date | Wed, 12 May 2010 13:07:34 -0400 | From | Mathieu Desnoyers <> | Subject | Re: Perf and ftrace [was Re: PyTimechart] |
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* Peter Zijlstra (peterz@infradead.org) wrote: > On Wed, 2010-05-12 at 18:46 +0200, Frederic Weisbecker wrote: > > But there is no strong reason for perf record not to use splice, > > a part the fact that perf doesn't support splice. > > > Its mostly an interface/api question. You cannot easily splice() a > mmap()'ed buffer on machines that have address constraints like sparc.
Ah ? Can you explain this issue a bit more ? There is possibly a concern I don't quite see here.
Thanks,
Mathieu
> > The thing I was thinking about is adding a new syscall that creates a > single buffer of specified size and provides a fd. Then use > PERF_EVENT_IOC_SET_OUTPUT, to connect an event to that fd/buffer and use > splice() on that fd. > > It could reuse most of the perf buffer code, but simply not map it into > userspace and therefore not have the restriction on the vaddr. > > Once you have that, a .splice_read implementation shouldn't be too hard. >
-- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com
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