On Mon, Feb 08, 2016 at 11:40:20AM +0000, Marc Zyngier wrote: > Programming the active state in the (re)distributor can be an > expensive operation so it makes some sense to try and reduce > the number of accesses as much as possible. So far, we > program the active state on each VM entry, but there is some > opportunity to do less. > > An obvious solution is to cache the active state in memory, > and only program it in the HW when conditions change. But > because the HW can also change things under our feet (the active > state can transition from 1 to 0 when the guest does an EOI), > some precautions have to be taken, which amount to only caching > an "inactive" state, and always programing it otherwise. > > With this in place, we observe a reduction of around 700 cycles > on a 2GHz GICv2 platform for a NULL hypercall. > > Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
