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    SubjectRe: perf_counter Atom patch
    From
    Yong,

    On Tue, Jun 23, 2009 at 10:27 AM, stephane
    eranian<eranian@googlemail.com> wrote:
    > Hi,
    >
    > On Tue, Jun 23, 2009 at 9:59 AM, Yong Wang<yong.y.wang@linux.intel.com> wrote:
    >> On Tue, Jun 23, 2009 at 09:45:03AM +0200, stephane eranian wrote:
    >>>
    >>> Unfortunately, I don't have a N270 to compare with your results.
    >>> We need to verify whether or not N270 implements the fixed counters.
    >>> Does it report architected perfmon v3 or v1?
    >>>
    >>
    >> All Atom processors report perfmon v3 as specified in SDM. N270 is no
    >> exception.
    >>
    > V3 does not set a minimal number of fixed counters, could be zero. But
    > that seems
    > odd. Let me ask around.
    >
    Second thought on this:
    x86_pmu.num_counters_fixed =
    max((int)edx.split.num_counters_fixed, 3);

    rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, x86_pmu.intel_ctrl);


    Forcing num_counter_fixed is not enough, you need to make sure they are actually
    activated in GLOBAL_CTRL, i.e., make sure bits 32-34 are set in intel_ctrl.
    Depending on which machine you're on, the power on value for GLOBAL_CTRL
    changes. The correct value for it should be that ONLY generic counters are on
    by default.


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