Re: [PATCH 1/10] Cr4 is valid on some 486s

[Arjan van de Ven]

On Mon, 2005-11-14 at 11:46 -0800, Zachary Amsden wrote:

> It seems that SMP vs. UP lock / spinlock overhead is relevant even for 
> future, multi-core CPUs in a virtualization context, as the notion of 
> hotplug here is based on scheduling constraints of the virtualization 
> engine, and the kernel can quite readily end up with only one VCPU.


this assumes that you don't just always want to assume and use SMP
primitives in a virtualized context. I sort of question that assumption;
sure these things have overhead, especially "lock", but if the solution
is more complexity and weird things to hide that half-percent or less of
performance difference... then do remember that such complexity is not
free either. Runtime tricks cost. 

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