Messages in this thread | | | Date | Tue, 28 Mar 2000 12:19:03 -0500 (EST) | From | Mark Hahn <> | Subject | Re: Timestamp counters on SMP |
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> see comments there. In general, I don't think you should count on TSC's > being syncronized at all - some people have computers with TSC's of > different rates (me included).
in this case, TSC is completely and utterly useless to user-space. there are only three sensible alternatives: - TSC's are incoherent and TSC's are turned off in user-space. - TSC's can be relied upon, and the kernel syncs them. - the kernel saves/restores TSC contents as necessary to make user-space see coherent time. ouch!
the sanity of SMP with different clocks is ambiguously in any case: the MPS standard says that OS's should merely try to function, but doesn't mandate any particular or sensible user-space behavior.
regards, mark hahn.
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