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    SubjectRe: [RFC PATCH 2/2] perf stat: Use event group to simulate PMI on PMI-less hardware counter
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    On Wed, 2010-11-10 at 14:15 +0800, Lin Ming wrote:
    > Some hardware counters(for example, Intel RAPL) can't generate interrupt
    > when overflow. So we need to simulate the interrupt to periodically
    > record the counter values. Otherwise, the counter may overflow and the
    > wrong value is read.
    >
    > This patch uses event group to simulate PMI as suggested by Peter
    > Zijlstra, http://marc.info/?l=linux-kernel&m=128220854801819&w=2
    >
    > create_group_counters() will create a group with 2 events, one hrtimer
    > based event as the group leader, and the other event to count. The
    > hrtimer is fired periodically, so the sibling event can record its
    > counter value periodically as well.

    I'm terribly confused here....

    - you introduce perf_event_attr:pmi_simulate, but then you never
    implement it -- nor do we need it afaict.


    - you use grouped counters for perf-stat, perf-stat doesn't use
    sampling so I don't see a need to group events to simulate the PMI.




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