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Re: [PATCH v3 7/8] perf: Define PMU_TXN_READ interface

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On Tue, Jul 21, 2015 at 06:50:45PM -0700, Sukadev Bhattiprolu wrote:
> We are trying to use the following interface:
> 
> 	start_txn(pmu, PERF_PMU_TXN_READ);
> 
> 	perf_event_read(leader);
> 	list_for_each(sibling, &leader->sibling_list, group_entry)
> 		perf_event_read(sibling)
> 
> 	pmu->commit_txn(pmu);
> 
> with the idea that the PMU driver would save the type of transaction in
> ->start_txn() and use in ->read() and ->commit_txn().
> 
> But since ->start_txn() and the ->read() operations could happen on different
> CPUs (perf_event_read() uses the event->oncpu to schedule a call), the PMU
> driver cannot use a per-cpu variable to save the state in ->start_txn().

> or is there better way?


I've not woken up yet, and not actually fully read the email, but can
you stuff the entire above chunk inside the IPI?

I think you could then actually optimize __perf_event_read() as well,
because all these events should be on the same context, so no point in
calling update_*time*() for every event or so.


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[PATCH v3 0/8] Implement group-read of events using txn interface Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> - 2015-07-15 05:10 +0200
  [PATCH v3 4/8] perf: Split perf_event_read() and perf_event_count() Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> - 2015-07-15 05:10 +0200
  [PATCH v3 7/8] perf: Define PMU_TXN_READ interface Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> - 2015-07-15 05:10 +0200
    Re: [PATCH v3 7/8] perf: Define PMU_TXN_READ interface Peter Zijlstra <peterz@infradead.org> - 2015-07-17 00:30 +0200
      Re: [PATCH v3 7/8] perf: Define PMU_TXN_READ interface Peter Zijlstra <peterz@infradead.org> - 2015-07-22 08:00 +0200
        Re: [PATCH v3 7/8] perf: Define PMU_TXN_READ interface Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> - 2015-07-23 01:30 +0200
          Re: [PATCH v3 7/8] perf: Define PMU_TXN_READ interface Peter Zijlstra <peterz@infradead.org> - 2015-07-23 10:10 +0200
            Re: [PATCH v3 7/8] perf: Define PMU_TXN_READ interface Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> - 2015-07-24 03:20 +0200
  [PATCH v3 3/8] perf: Add a flags parameter to pmu txn interfaces Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> - 2015-07-15 05:10 +0200
    Re: [PATCH v3 3/8] perf: Add a flags parameter to pmu txn interfaces Peter Zijlstra <peterz@infradead.org> - 2015-07-16 22:20 +0200
      Re: [PATCH v3 3/8] perf: Add a flags parameter to pmu txn interfaces Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> - 2015-07-16 23:30 +0200
    Re: [PATCH v3 3/8] perf: Add a flags parameter to pmu txn interfaces Peter Zijlstra <peterz@infradead.org> - 2015-07-16 22:50 +0200
  [PATCH v3 5/8] perf: Split perf_event_read_value() Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> - 2015-07-15 05:10 +0200
    Re: [PATCH v3 5/8] perf: Split perf_event_read_value() Peter Zijlstra <peterz@infradead.org> - 2015-07-16 23:20 +0200
      Re: [PATCH v3 5/8] perf: Split perf_event_read_value() Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> - 2015-07-16 23:50 +0200
    Re: [PATCH v3 5/8] perf: Split perf_event_read_value() Peter Zijlstra <peterz@infradead.org> - 2015-07-23 09:50 +0200
  [PATCH v3 1/8] powerpc/perf/hv-24x7: Whitespace - fix parameter alignment Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> - 2015-07-15 05:10 +0200
    Re: [v3,1/8] powerpc/perf/hv-24x7: Whitespace - fix parameter alignment Michael Ellerman <mpe@ellerman.id.au> - 2015-08-03 03:40 +0200
  [PATCH v3 2/8] powerpc/perf/hv-24x7: Simplify extracting counter from result buffer Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> - 2015-07-15 05:10 +0200
    Re: [v3, 2/8] powerpc/perf/hv-24x7: Simplify extracting counter from result buffer Michael Ellerman <mpe@ellerman.id.au> - 2015-08-03 03:40 +0200

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