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SubjectRe: [PATCH 0/3] Remove interrupt stack table usage from x86_64 kernel
On Sun, Dec 28, 2008 at 10:08:35PM +0200, Avi Kivity wrote:
> Avi Kivity wrote:
> >Avi Kivity wrote:
> >>1. Add per-cpu IDT
> >
> >Or we could have just two IDTs - one with IST and one without. I
> >clocked LIDT at 58 cycles (and we need two per heavyweight switch), so
> >it's not that wonderful.
>
> This makes the whole thing unworthwhile. The vmload/vmsave pair costs
> only 200 cycles (I should have started with this), and 120 cycles on the
> heavyweight path plus complexity are not worth 200 cycles on the
> lightweight path.

Actually to switch ISTs you need to change the TSS, not the IDT.
But I suppose that won't be any faster.

-Andi
--
ak@linux.intel.com


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