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    SubjectRe: Intel P6 vs P7 system call performance
    Benjamin LaHaise wrote:
    > On Tue, Dec 17, 2002 at 10:57:29AM -0800, Ulrich Drepper wrote:
    >>But this is exactly what I expect to happen. If you want to implement
    >>gettimeofday() at user-level you need to modify the page. Some of the
    >>information the kernel has to keep for the thread group can be stored in
    >>this place and eventually be used by some uerlevel code executed by
    >>jumping to 0xfffff000 or whatever the address is.
    > You don't actually need to modify the page, rather the data for the user
    > level gettimeofday needs to be in a shared page and some register (like
    > %tr) must expose the current cpu number to index into the data. Either
    > way, it's an internal implementation detail for the kernel to take care
    > of, with multiple potential solutions.

    That's not the problem... the problem is that the userland code can get
    preempted at any time and rescheduled on another CPU.


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