On Wed, Dec 16, 2020 at 04:23:22PM +0100, Paolo Bonzini wrote: > On 16/12/20 16:12, Michael Roth wrote: > > It looks like it does save us ~20-30 cycles vs. vmload, but maybe not > > enough to justify the added complexity. Additionally, since we still > > need to call vmload when we exit to userspace, it ends up being a bit > > slower for this particular workload at least. So for now I'll plan on > > sticking to vmload'ing after vmexit and moving that to the asm code > > if there are no objections. > > Yeah, agreed. BTW you can use "./x86/run x86/vmexit.flat" from > kvm-unit-tests to check the numbers for a wide range of vmexit paths. Wasn't aware of that, this looks really useful. Thanks! > > Paolo > > > current v2 patch, sample 1 > > ioctl entry: 1204722748832 > > pre-run: 1204722749408 ( +576) > > post-run: 1204722750784 (+1376) > > ioctl exit: 1204722751360 ( +576) > > total cycles: 2528 > > > > current v2 patch, sample 2 > > ioctl entry: 1204722754784 > > pre-vmrun: 1204722755360 ( +576) > > post-vmrun: 1204722756720 (+1360) > > ioctl exit: 1204722757312 ( +592) > > total cycles 2528 > > > > wrgsbase, sample 1 > > ioctl entry: 1346624880336 > > pre-vmrun: 1346624880912 ( +576) > > post-vmrun: 1346624882256 (+1344) > > ioctl exit: 1346624882912 ( +656) > > total cycles 2576 > > > > wrgsbase, sample 2 > > ioctl entry: 1346624886272 > > pre-vmrun: 1346624886832 ( +560) > > post-vmrun: 1346624888176 (+1344) > > ioctl exit: 1346624888816 ( +640) > > total cycles: 2544 > > >
