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    SubjectRe: perf_counters: page fault trace record
    Ingo Molnar wrote:
    > * Paul Mackerras <> wrote:
    >> Corey Ashford writes:
    >>> Paul Mackerras wrote:
    >>>> Can't you do what you need just using a page fault software
    >>>> counter with sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_ADDR
    >>>> and sample_period = 1?
    >>> I thought about that, but I was under the (incorrect?)
    >>> impression that on Power, the PERF_SAMPLE_ADDR would be set by
    >>> the value of the SDAR register, which wouldn't be correct for
    >>> the case of a page fault.
    >> No, the PERF_SAMPLE_ADDR value only comes from SDAR for a hardware
    >> counter overflow event. For the page-fault software counter the
    >> PERF_SAMPLE_ADDR value will always be the faulting address.
    > Corey, could you please add support for it in 'perf'? We dont want
    > such sw-counter features to be in the kernel code without matching
    > support in tools/perf/.
    > While user data symbols wont be resolved, if we have a
    > --target-address switch in perf record we could see the faulting
    > frequency (and the fault coverage - and ordering as well) of shared
    > libraries, in perf report and perf annotate.
    > This would be a very useful facility.
    > Thanks,
    > Ingo

    I'll see what I can do. This will be my first time modifying perf, so expect
    that I won't do things the way you prefer the first couple of go-arounds :)


    - Corey

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