[libvirt] libvirt domblkstat result is quite different from the info acquired from "/proc/[pid]/io"

Hi, all. I’m current doing monitoring jobs(CPU, memory and disk utilisation) on some KVM-based VMs using libvirt, but i came to some confusions. For the disk data(blkstat), I find that the results acquired by virDomainBlockStats is not consistent with the value read from /proc/[vm_pid]/io(i only care “rd_bytes" and “wr_bytes"), since libvirt doesn’t support host level monitoring, i have to calculate the host’s disk utilisation by using the /proc/diskstats. The weird thing is that individual VM’s disk data can be greater that the total disk’s during some sampling time. Can someone explain this ?