Lucas Nussbaum wrote:
On 28/04/09 at 12:56 +0200, Lucas Nussbaum wrote:
I then upgraded to kvm-85 (both the host kernel modules and the
userspace), and re-ran the tests. Performance is better (about 85 MB/s),
but still very far from the non-virtio case.
I forgot to mention that the strangest result I got was the total amount
of write blocks queued (as measured by blktrace). I was writing a 1 GB
file to disk, which resulted in:
- 1 GB of write blocks queued without virtio
- ~1.7 GB of write blocks queued with virtio on kvm 84
- ~1.4 GB of write blocks queued with virtio on kvm 85
I don't understand with kvm with virtio writes "more blocks than
necessary", but that could explain the performance difference.
Are these numbers repeatable?
Try increasing the virtio queue depth. See the call to
virtio_add_queue() in qemu/hw/virtio-blk.c.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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