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    SubjectRe: [PATCH] Turn rdmsr, rdtsc into inline functions, clarify names
    On Mon, Aug 07, 2006 at 02:56:39PM +0200, Andi Kleen wrote:
    > On Mon, Aug 07, 2006 at 02:48:55PM +0200, Vojtech Pavlik wrote:
    > > On Mon, Aug 07, 2006 at 02:28:45PM +0200, Andi Kleen wrote:
    > > > On Mon, Aug 07, 2006 at 01:09:31PM +0200, Vojtech Pavlik wrote:
    > > > > On Mon, Aug 07, 2006 at 10:48:50AM +0200, Andi Kleen wrote:
    > > > > > On Sun, Aug 06, 2006 at 10:43:44PM -0400, Dmitry Torokhov wrote:
    > > > > > > On Saturday 05 August 2006 23:16, Andi Kleen wrote:
    > > > > > > > This whole thing is broken, e.g. on a preemptive kernel when the
    > > > > > > > code can switch CPUs
    > > > > > > >
    > > > > > >
    > > > > > > Would not preempt_disable fix that?
    > > > > >
    > > > > > Partially, but you still have other problems. Please just get rid
    > > > > > of it. Why do we have timer code in the kernel if you then chose
    > > > > > not to use it?
    > > > >
    > > > > The problem is that gettimeofday() is not always fast.
    > > >
    > > > When it is not fast that means it is not reliable and then you're
    > > > also not well off using it anyways.
    > >
    > > I assume you wanted to say "When gettimeofday() is slow, it means TSC is
    > > not reliable", which I agree with.
    > >
    > > But I need, in the driver, in the no-TSC case use i/o counting, not a
    > > slow but reliable method. And I can't say, from outside the timing
    > > subsystem, whether gettimeofday() is fast or slow.
    >
    > Hmm if that is the only obstacle I can export a "slow gettimeofday" flag.

    That would help.

    > However it would be some work to implement it for all architectures.
    >
    > > I assume we could make it work with the monotonic timer instead.
    >
    > The monotonic timer is the right thing to use to make you independent
    > of ntpd, but it's normally not faster or slower than gettimeofday.

    Yup.

    --
    Vojtech Pavlik
    Director SuSE Labs
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