Re: [RFC PATCH 2/4] x86, mwaitt: introduce mwaitx idle with a configurable timer

Borislav Petkov
2015-05-21T16:02:30Z

On Thu, May 21, 2015 at 10:56:32PM +0800, Huang Rui wrote:
> Looks like good use case. Boris, could we try to implement it?

Andy had some suggestions on how to do it here:

https://lkml.kernel.org/r/555D3629.8080002@kernel.org

which should be doable. Also, you'd probably need to set ECX[0]=0b too,
so that MWAITX doesn't get woken up by interrupts while MWAIT-ing with
interrupts disabled. I.e., this sequence:

cli
rdtsc
shove the computed timeout into ebx
mov $2,%ecx # this enables the timer and disables IRQs while MWAITing
mwaitx
sti

The NMI argument is a problem though - if and NMI gets you out of
MWAITX, a simple perf tool workload would kill all MWAITX executions.
Which is bad. :-\

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
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