Messages in this thread | | | Date | Mon, 16 Dec 2002 22:43:30 -0800 (PST) | From | dean gaudet <> | Subject | Re: Intel P6 vs P7 system call performance |
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On Mon, 16 Dec 2002, Linus Torvalds wrote:
> It's not as good as a pure user-mode solution using tsc could be, but > we've seen the kinds of complexities that has with multi-CPU systems, and > they are so painful that I suspect the sysenter approach is a lot more > palatable even if it doesn't allow for the absolute best theoretical > numbers.
don't many of the multi-CPU problems with tsc go away because you've got a per-cpu physical page for the vsyscall?
i.e. per-cpu tsc epoch and scaling can be set on that page.
the only trouble i know of is what happens when an interrupt occurs and the task is rescheduled on another cpu... in theory you could test %eip against 0xfffffxxx and "rollback" (or complete) any incomplete gettimeofday call prior to saving a task's state. but i bet that test is undesirable on all interrupt paths.
-dean
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