On 03/15/2010 08:11 AM, 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.
VMREAD/VMWRITEs are generally optimized by hypervisors as they tend to
be costly. KVM is a bit unusual in terms of how many times the
instructions are executed per exit.
Regards,
Anthony Liguori
