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    SubjectRe: [tip:perfcounters/core] perf_counter: x86: Fix call-chain support to use NMI-safe methods
    On Mon, 2009-06-15 at 14:59 -0400, Mathieu Desnoyers wrote:
    > * Peter Zijlstra ( wrote:
    > > On Mon, 2009-06-15 at 14:48 -0400, Mathieu Desnoyers wrote:
    > > > we should not care that much about the performance hit of
    > > > saving/restoring the cr2 register at each nmi entry/exit.
    > >
    > > But we do, perf counters very much cares about nmi performance.
    > >
    > To a point where it cannot afford a simple register save/restore ?
    > There is "caring" and "_caring_". I am tempted to ask what NMI handler
    > execution frequency you have in mind here to figure out if we are not
    > trying to optimize sub-nanoseconds per minutes. ;)

    Ah, well, I have no idea who expensive cr2 is, if its like a regular
    register then it should be fine. If however its tons more expensive then
    we should really avoid it.

    As to the freq, 100kHz would be nice ;-)

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