Lucas Nussbaum wrote:
Hi, I'm experiencing bad disk I/O performance using virtio disks. I'm using Linux 2.6.29 (host & guest), kvm 84 userspace. On the host, and in a non-virtio guest, I get ~120 MB/s when writing with dd (the disks are fast RAID0 SAS disks).
Could you provide detail of the exact type and size of i/o load you were creating with dd? Also the full qemu cmd line invocation in both cases would be useful.
In a guest with a virtio disk, I get at most ~32 MB/s.
Which non-virtio interface was used for the comparison?
The rest of the setup is the same. For reference, I'm running kvm -drive file=/tmp/debian-amd64.img,if=virtio. Is such performance expected? What should I check?
Not expected, something is awry. blktrace(8) run on the host will shed some light on the type of i/o requests issued by qemu in both cases. -john -- john.cooper@xxxxxxxxxxxxxxxxxx -- 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
