Messages in this thread | | | Date | Sun, 28 Dec 2008 21:34:25 +0100 | From | Andi Kleen <> | Subject | Re: [PATCH 0/3] Remove interrupt stack table usage from x86_64 kernel |
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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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