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    SubjectRe: [-mm patch] x86_64 GTOD: offer scalable vgettimeofday II
    Date
    On Thursday 01 February 2007 12:46, Ingo Molnar wrote:
    >
    > * jbohac@suse.cz <jbohac@suse.cz> wrote:
    >
    > > Inter-CPU monotonicity can not, however, be guaranteed in a vsyscall,
    > > so vsyscall is not used by default. [...]
    >
    > note that this is not actually the case. My patch below, ontop of -mm,
    > implements a fully monotonic gettimeofday as an optional vsyscall
    > feature.
    >
    > The 'price' paid for it is lower resolution - but it's still good for
    > those benchmarking TPC-C runs - and /alot/ simpler.

    BTW another comment: I was told that at least one of the big databases
    wants ms resolution here. So to make your scheme work
    would require a HZ=1024 regular interrupt. But that would also make
    everything slower again due to CPU overhead as it was learned in the 2.4->2.6 HZ
    transition.

    So it might not actually be worth it.

    -Andi

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