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DateFri, 16 Nov 2007 08:17:08 +0100
FromIngo Molnar <>
SubjectRe: x86: disable preemption in delay_tsc()

* Andrew Morton <akpm@linux-foundation.org> wrote:

> It sounds like it would work OK. What is the setup cost for a usleep?
> I'd have thought that code which does something like
>
> while (i++ < 1000) {
> foo();
> udelay(1);
> }
>
> would take qiute a bit longer with such a change?

full roundtrip cost ought to be below 10 usecs, depending on the system.
There's no problem doing a non-preemptible udelay up to 10 usecs and we
could use usleep above that.

Ingo
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