Host processes priority over guests

Hello all,

we are currently evaluating a migration from Xen to KVM.

We host our VMs on a SAN, access to LUNs is done by the iSCSI protocol, all multipathed.

With Xen, we faced a problem when VMs were consuming a lot of CPU and a lot of I/O. In this situation, the Dom0 did not get enough CPU time to process the I/O requests through the iSCSI processes and to run the iscsid daemon. So, the Dom0 was always loosing the iSCSI connection to the SAN because of timeout (node.conn[0].timeo.noop_out_timeout).

We solved it by dedicating a core to the Dom0, as recommended in the Xen FAQ.

Can this happen with KVM ? Why can(not) it happen ? If it could happen, what is the recommended solution (renice, cgroups, ...) ?

Thanks for your help.

Romain LE DISEZ