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SubjectRe: HT and idle = poll

On 6 Mar 2003, Alan Cox wrote:
> On Thu, 2003-03-06 at 19:30, Linus Torvalds wrote:
> > >So, don't use idle=poll with HT when you know your workload has idle time! I
> > >have not tried oprofile, but it stands to reason that this would be a
>
> idle=poll probably needs to be doing "rep nop" in a tight loop.

We already do that. It's not enough. The HT thing will still steal cycles
continually, since the "rep nop" is really only equivalent to a
"sched_yield()".

Think of "rep nop" as yielding, and "mwait" as a true wait.

(I don't actually have any real information on "mwait", so I may be wrong
about the details on the new instructions. They looked obvious enough,
though).

Linus

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