<html> <head> <meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type"> </head> <body text="#000000" bgcolor="#FFFFFF"> <div class="moz-cite-prefix">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: <a class="moz-txt-link-freetext" href="http://pic.dhe.ibm.com/infocenter/lnxinfo/v3r0m0/index.jsp?topic=/liaat/liaattunkickoff.htm">http://pic.dhe.ibm.com/infocenter/lnxinfo/v3r0m0/index.jsp?topic=/liaat/liaattunkickoff.htm</a> It's quite a good starting point. Regards, On 01/19/2014 08:01 PM, Matteo Lanati wrote: </div> <blockquote cite="mid:CABWEt4aiAYPC0zGLj2kY1akEJtckQSN+MKCNTEzGP4Mp59mjWw@mail.gmail.com" type="cite"> <pre wrap="">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 <a class="moz-txt-link-abbreviated" href="mailto:5140@2.33">5140@2.33</a> 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 </pre> <fieldset class="mimeAttachmentHeader"></fieldset> <pre wrap="">_______________________________________________ libvirt-users mailing list <a class="moz-txt-link-abbreviated" href="mailto:libvirt-users@redhat.com">libvirt-users@redhat.com</a> <a class="moz-txt-link-freetext" href="https://www.redhat.com/mailman/listinfo/libvirt-users">https://www.redhat.com/mailman/listinfo/libvirt-users</a></pre> </blockquote> <pre class="moz-signature" cols="72">-- Pierre Schweitzer <a class="moz-txt-link-rfc2396E" href="mailto:pierre@reactos.org"><pierre@reactos.org></a> System Administrator ReactOS Foundation</pre> </body> </html>