Messages in this thread | | | Date | Thu, 22 Sep 2005 10:00:47 +0200 | From | Jonas Oreland <> | Subject | Re: [discuss] Re: [PATCH] x86-64: Fix bad assumption that dualcore cpus have synced TSCs |
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Ray Bryant wrote: > On Wednesday 21 September 2005 10:04, Andi Kleen wrote: > > >>We handle this, but single socket dual core was special cased because >>I was told previously it should be ok. >> >>-Andi > > > AFAIK there is a processor state bit that enables/disables this behavior. > Apparently some BIOS's are setting this one way for desktop systems and the > other way for servers. If it is thought to be important I can track that > down and see if it can be externally documented. (It may actually be in the > bios and kernel developer guide...) >
Hi,
This would be very good (for us single socket dual core users) I tried a very small benchmark:
clock_gettime(CLOCK_REALTIME): elapsed 7336657 -> 733.665700ns/call clock_gettime(CLOCK_PROCESS_CPUTIME_ID): elapsed 763247 -> 76.324700ns/call
It's a factor 10 faster if the TSC were to be in sync.
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