Re: [Qemu-devel] virtio-scsi vs. virtio-blk

[Stefan Hajnoczi]

On Thu, Aug 9, 2012 at 8:41 AM, Stefan Priebe <address@hidden> wrote:
> starting line:
> /usr/bin/qemu-x86_64 -chardev
> socket,id=qmp,path=/var/run/qemu-server/103.qmp,server,nowait -mon
> chardev=qmp,mode=control -pidfile /var/run/qemu-server/103.pid -daemonize
> -usbdevice tablet -name kvmcrash -smp sockets=1,cores=8 -nodefaults -boot
> menu=on -vga cirrus -k de -device
> virtio-scsi-pci,id=scsihw0,bus=pci.0,addr=0x5 -drive
> file=iscsi://10.0.255.100/iqn.1986-03.com.sun:02:8a9019a4-4aa3-cd8a-f723-f05db9085ef9/0,if=none,id=drive-scsi1,cache=writethrough,aio=native
> -device
> scsi-hd,bus=scsihw0.0,channel=0,scsi-id=0,lun=1,drive=drive-scsi1,id=scsi1
> -drive
> file=iscsi://10.0.255.100/iqn.1986-03.com.sun:02:8a9019a4-4aa3-cd8a-f723-f05db9085ef9/2,if=none,id=drive-virtio0,cache=writethrough,aio=native
> -device virtio-blk-pci,drive=drive-virtio0,id=virtio0,bus=pci.0,addr=0xa
> -drive
> file=iscsi://10.0.255.100/iqn.1986-03.com.sun:02:8a9019a4-4aa3-cd8a-f723-f05db9085ef9/1,if=none,id=drive-scsi0,cache=writethrough,aio=native
> -device
> scsi-hd,bus=scsihw0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0,id=scsi0,bootindex=102
> -m 4096 -netdev
> type=tap,id=net0,ifname=tap103i0,script=/var/lib/qemu-server/pve-bridge,vhost=on
> -device
> virtio-net-pci,mac=BA:5B:86:AD:14:3A,netdev=net0,bus=pci.0,addr=0x12,id=net0,bootindex=300

You're running qemu.git?  In that case make sure to use -enable-kvm,
otherwise you get TCG (dynamic binary translator) instead of using the
CPU's hardware virtualization extensions.

qemu-kvm.git enables KVM by default so this could explain slowness if
you've run distro qemu-kvm binaries or qemu-kvm.git in the past.