On Mon, Mar 15, 2010 at 03:11:42PM +0200, Avi Kivity wrote: > On 03/15/2010 03:03 PM, Joerg Roedel wrote: >> >>>> I will add another project - iommu emulation. Could be very useful >>>> for doing device assignment to nested guests, which could make >>>> testing a lot easier. >>>> >>> Our experiments show that nested device assignment is pretty much >>> required for I/O performance in nested scenarios. >>> >> Really? I did a small test with virtio-blk in a nested guest (disk read >> with dd, so not a real benchmark) and got a reasonable read-performance >> of around 25MB/s from the disk in the l2-guest. >> >> > > Your guest wasn't doing a zillion VMREADs and VMWRITEs every exit. > > I plan to reduce VMREAD/VMWRITE overhead for kvm, but not much we can do > for other guests. Does it matter for the ept-on-ept case? The initial patchset of nested-vmx implemented it and they reported a performance drop of around 12% between levels which is reasonable. So I expected the loss of io-performance for l2 also reasonable in this case. My small measurement was also done using npt-on-npt. Joerg -- 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
