Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [patch] Mark rdtsc as sync only for netburst, not for core2 | Date | Tue, 28 Nov 2006 11:36:28 +0100 |
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On Tuesday 28 November 2006 11:28, Arjan van de Ven wrote: > Hi, > > On the Core2 cpus, the rdtsc instruction is not serializing (as defined > in the architecture reference since rdtsc exists) and due to the deep > speculation of these cores, it's possible that you can observe time go > backwards between cores due to this speculation. Since the kernel > already deals with this with the SYNC_RDTSC flag, the solution is > simple, only assume that the instruction is serializing on family 15... > > The price one pays for this is a slightly slower gettimeofday (by a > dozen or two cycles), but that increase is quite small to pay for a > really-going-forward tsc counter.
Added thanks
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