On Fri, Feb 18, 2011 at 12:07 PM, erik quanstrom <quans...@quanstro.net> wrote:
>> The high level overview is that it is stored in a shared page, mapped
>> into each new process's memory space at start-up. The kernel is never
>> entered; there are no context switches. The kernel has a timer that
>> updates this page atomically.
>
> i wonder if that is uniformly faster.  consider that
> making reads of that page coherent enough on a
> big multiprocessor and making sure there's not too
> much interprocesser skew might be slower than a
> system call.

are you claiming that

    enter system call
    look at kernel data page to figure out time
    exit system call

could be faster than

    look at kernel data page to figure out time

?

either way the memory accesses in the middle
are the same.

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