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    SubjectRe: [RT] read_tsc: ACK! TSC went backward! Unsynced TSCs?
    On Tue, Nov 29, 2005 at 08:52:19AM -0800, thockin@hockin.org wrote:
    > On Tue, Nov 29, 2005 at 07:06:24AM -0700, Andi Kleen wrote:
    > > But I'm surprised you're saying 2.6.11 broke. At least 2.6.11 64bit should
    > > have always used HPET in this case. I only broke it around 2.6.13
    > > where I added an overeager optimization for single socket DC on my side based
    > > on a misunderstanding. Earlier and later kernels should have been ok.
    >
    > we didn't have HPET enabled in BIOS until recently. Turning that on made
    > all the TSC gettimeofday() crap disappear. Now to find and kill any
    > straggling users of rdtsc

    The newer kernels work around this too by using pmtimer when needed.
    Of course it's slow.

    Regarding straggling users of rdtsc - one way would be to optionally
    trap them and log them in the kernel. That would work in ring 3 at least.

    -Andi

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