Re: [PATCH] x86, acpi, idle: Restructure the mwait idle routines

[Arjan van de Ven]

On 11/20/2013 2:58 AM, Peter Zijlstra wrote:
> On Wed, Nov 20, 2013 at 11:28:03AM +0100, Peter Zijlstra wrote:
> > On Tue, Nov 19, 2013 at 01:06:30PM -0800, Jacob Pan wrote:
> > > I applied this patch on top of upstream kernel (801a760) and found out
> > > my machine completely failed to enter idle when nothing is running.
> > > turbostate shows 100% C0. ftrace shows kernel coming in and out of idle
> > > frequently.
> > >
> > > Both ACPI idle and intel_idle behaves the same way. I have to do the
> > > following change to allow entering C-states again.
>
> > That doesn't make any sense; current_set_polling_and_test() returns the
> > same thing need_resched() does.
> >
> > But you're right, intel_idle resides 100% in C0 and acpi_idle has 100%
> > C1 residency... most weird.
>
> So pretty silly actually; you cannot do a store (any store) in between
> monitor and mwait.

you can
just not to the cacheline you are watching (or things that alias with that)

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