Re: [PATCH 7/7] x86,idle: do not leave mm in idle state

[Rik van Riel <riel@surriel.com>]

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On Fri, 2018-06-22 at 09:01 -0700, Andy Lutomirski wrote:
> Hmm, fair enough.  I think a better heuristic would be if the
> estimated idle duration is more than, say, 10ms.  I *think* the code
> has been cleaned up enough that this is easy now.  (Using time
> instead
> of C6 will make it a lot less dependent on which idle driver is in
> use.)

This particular bit of code is only in intel_idle
though, and not every cpuidle governor estimates
an idle duration, nor does it get passed up the
stack (presumably because it not always exists).

I will just drop this patch for now, and see if
adding back in the patch that skips manipulation
of the mm_cpumask(&init_mm), since that might make
leave_mm() a little cheaper.

We would still have excess manipulation of the
bitmask when re-entering the task from what should
have been lazy TLB mode, but total cache line
contention would likely still be down from where
it is before that patch.

-- 
All Rights Reversed.

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