[libvirt] How can I improve the performance of libvirt when running many virtual machines on same host

Hi, I am using Xen 4 as hypervisor and using libvirt 0.8.4 to communicate with it. When I run more than 35 virtual machines on the host, Libvirt starts to run extremely slow and I cant even execute a /"virsh list/". The memory usage of libvirtd is around 468288K. Is there any way to improve the performance of libvirt? Is there any maximum number of virtual machines libvirt can manage without having a poor performace? Best Regards, Diego Dias