Re: 2.6.18-rc6-mm1: GPF loop on early boot

[Jeremy Fitzhardinge]

Ingo Molnar wrote:
> another thing about i386-pda: why did you pick the %gs selector to store 
> the PDA in? %fs would be a better choice because %gs is used by glibc so 
> the saving/restoring of %fs would likely be near zero-cycles cost. 
> (instead of the current 9 cycles for saving/restoring %gs)
>   

Why would saving/restoring %fs be quicker?  The main reason I chose %gs 
was so that it didn't add anything to the context switch time (since %gs 
needed to be switched anyway), and it leaves open the possibility of 
using gcc's TLS support in the kernel (I have a working demonstration of 
this, but Rusty and I are still working out the module details).

   J
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