Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [patch 9/9] Make use of the Master Timer | Date | Fri, 2 Feb 2007 08:04:29 +0100 |
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On Thursday 01 February 2007 15:29, Jiri Bohac wrote:
> If I do: > rdtscll(a) > ... > rdtscll(b) > is it guaranteed that (b > a) ?
It's not architecturally -- unless you have a barrier.
On P4 the micro architecture guarantees it, but there the barrier in get_cycles_sync is patched away. On other x86-64s it is generally needed.
The effect can be also seen between CPUs.
> Because of the __vxtime.cpu[cpu].tsc_invalid flag. We may be
You can still precompute it for the HPET etc. case. They are already slow, but saving a condition there might be still worth it.
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