Re: [patch 13/14] x86_64: Use common functions in cluster and physflat mode

[Andi Kleen]

On Tue, Sep 13, 2005 at 07:53:03AM -0700, Zwane Mwaikambo wrote:
> On Tue, 13 Sep 2005, Andi Kleen wrote:
> 
> > > We should probably remove the !HOTPLUG case and just use the mask version
> > > for all cases <=8 CPUS, use physflat or the cluster mode for >8cpus as 
> > > the case may be, instead of defaulting to sequence_IPI which seems
> > > a little overkill for the intended purpose.
> > 
> > Or just always use physflat and remove the logical flat case? 
> > That seems cleanest to me. Any objections? 
> 
> My objection is the number of APIC writes required to issue IPIs to a 
> group of processors, however i do understand that it would help 

local APIC accesses are cheap, they don't go over any external bus.
It's not like a PCI cycle.

> maintainability and testing coverage if we reduce the number of operating 
> modes, are you proposing physflat for _everything_ ?

On everything that's currently run by flat yes. Possibly the others
too when tested.

-Andi
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