Mark Hahn wrote:
>
> > 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!
>
Why would you want to use TSC in the user space? Coherent time and TSC
are two different things. I think relying on TSC content in the user
space is like relying on content of any other register, we don't expect
eax to have any particular value ;-)
> 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.
Boris
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