Re: [PATCH] i386-pda UP optimization

[Jeremy Fitzhardinge]

Arjan van de Ven wrote:
> segment register accesses really are not cheap. 
> Also really it'll be better to use the register userspace is not using,
> but we had that discussion before; could you remind me why you picked 
> %gs in the first place?
>   

To leave open the possibility of using the compiler's TLS support in the
kernel for percpu.  I also measured the cost of reloading %gs vs %fs,
and found no difference between reloading a null selector vs a non-null
selector.

    J

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