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Date: Mon, 17 Nov 2014 13:45:18 -0800 From: Andi Kleen <ak@...ux.intel.com> To: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org, Robert Richter <rric@...nel.org>, Frederic Weisbecker <fweisbec@...il.com>, Mike Galbraith <efault@....de>, Paul Mackerras <paulus@...ba.org>, Stephane Eranian <eranian@...gle.com>, kan.liang@...el.com, adrian.hunter@...el.com, markus.t.metzger@...el.com, mathieu.poirier@...aro.org, acme@...radead.org, Peter Zijlstra <peterz@...radead.org>, Michael Ellerman <michaele@....ibm.com> Subject: Re: [PATCH v8 02/14] perf: Add AUX area to ring buffer for raw data streams On Mon, Nov 17, 2014 at 01:24:00PM -0800, Sukadev Bhattiprolu wrote: > Alexander Shishkin [alexander.shishkin@...ux.intel.com] wrote: > | From: Peter Zijlstra <peterz@...radead.org> > | > | This patch introduces "AUX space" in the perf mmap buffer, intended for > | exporting high bandwidth data streams to userspace, such as instruction > | flow traces. > | > | AUX space is a ring buffer, defined by aux_{offset,size} fields in the > | user_page structure, and read/write pointers aux_{head,tail}, which abide > | by the same rules as data_* counterparts of the main perf buffer. > > The "format" of this raw stream of data can differ across processors > (and architecutres) correct ? i.e the perf tool processing of this > aux data will also differ across processors ? Yes. The main caveat is that you need special handling code in perf. > > Power8 processors support what we call 24x7 counters that collect info > on a large number of events. The current 24x7 support in > (arch/powerpc/perf/hv-24x7.c) currently uses reading one counter at a > time using the pmu->read() interface. > > We are looking for ways to export much larger number of counters through > one pmu->read() or another call. I am trying to see if the hv-24x7 pmu > could use this aux interface and then have/implement a helper in perf > tool to extract the counter values. It's probably only worth it if your amount of data is extremely high and has to be to compressed (like in PT -- no choice, cannot do it otherwise) If your data amounts are more reasonable it will be a lot simpler to stay with the current perf interfaces, even though they have a bit higher overhead. -Andi -- ak@...ux.intel.com -- Speaking for myself only -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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