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

Jeremy Fitzhardinge
2006-09-11T07:31:52Z

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