Hey, First of all, you don't need to set scheduler as deadline on VM. Just disable it (elevator=none). The HV will handle it for the VM.
Furthermore, as generic performance optimization, I recommend you disable swappiness on the HV, as well as zone reclaim. I invite you to read this IBM paper: http://pic.dhe.ibm.com/infocenter/lnxinfo/v3r0m0/index.jsp?topic=/liaat/liaattunkickoff.htm It's quite a good starting point. Regards, On 01/19/2014 08:01 PM, Matteo Lanati wrote: > Hi all, > > I'm running a VM using libvirt+KVM and I have a disk performance issue. > > The host is the following: > 4 cores Intel Xeon [email protected] GHz, 16 GB of RAM, SATA HDD, OS Debian Wheezy, > libvirt 0.9.12-11, QEMU-KVM 1.1.2+dfsg-2. > > The guest: > 1 CPU, 2 GB RAM running Debian 7.0, image in compressed qcow2 format. > > When I try do run "dd if=/dev/zero of=io.test bs=32768k count=40" I get > around 500 MB/s on bare metal, while only around 30 MB/s inside the VM. > > I'm trying to get something more out of the virtualization layer, I hope > that there's room for improvement. > > I'm using virtio, I aready set cache='none' and io='native' in the domain > definition. Both host and guest are using deadline as I/O scheduler. The VM > uses an ext4 filesystem, while the image is saved on an ext3 disk. I > mounted the host and guest filesystems specifying nodiratime and noatime > options. Even if I convert the image to raw format nothing changes. > I didn't mess with iotune nor blockio. > > Is there something that I overlooked or any other suggestion? > > Thanks in advance for your help. > > Matteo > > > > > > _______________________________________________ > libvirt-users mailing list > [email protected] > https://www.redhat.com/mailman/listinfo/libvirt-users -- Pierre Schweitzer <[email protected]> System Administrator ReactOS Foundation
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