Re: [RFC PATCH 3/3] idle: store the idle state index in the struct rq

[Peter Zijlstra <peterz@infradead.org>]

On Tue, Feb 11, 2014 at 09:12:02AM -0800, Arjan van de Ven wrote:
> On 2/11/2014 8:41 AM, Peter Zijlstra wrote:
> >On Mon, Feb 03, 2014 at 08:17:47AM -0800, Arjan van de Ven wrote:
> >>On 2/3/2014 6:56 AM, Peter Zijlstra wrote:
> >>if there's a simple api like
> >>
> >>sched_cpu_cache_wiped(int llc)
> >>
> >>that would be very nice for this; the menuidle side knows this
> >>for some cases and thus can just call it. This would be a very
> >>small and minimal change
> >>
> >>* if you don't care about llc vs core local caches then that
> >>   parameter can go away
> >>
> >>* I assume this is also called for the local cpu... if not then we
> >>   need to add a cpu number argument
> >>
> >>* we can also call this from architecture code when wbinvd or the
> >>   arm equivalent is called etc
> >
> >A little something like so?
> >
> 
> is there value also in doing a cpu level cache flush?
> (cpu cache flush we know from the C state, for the llc cache flush we need to read an MSR
> on x86. Not insane expensive but not zero either)

L1 or L2? L1 is too small to really bother afaik and L2 is shared
between logical cpus so we'd need a mask there, not sure the generic
topology has that.

I'll have a quick peek later.