Hi, I have the following configuration: Box: 24GB RAM, 1 physical CPU, 8 cores, 2TB disk OS: Ubuntu 12.04.4 LTS GRUB_CMDLINE_XEN_DEFAULT="dom0_mem=6500M dom0_max_vcpus=2 dom0_vcpus_pin" Xen 4.2.2 dom0 - 2VCPUs, 6GB RAM domU - each domain gets 1 VCPU, 1GB RAM 15 domains Im confused about xentop reporting 8 - 10% CPU Utilization on dom0, idle dom0, where mpstat or sysrec [1] shows a lower value of something between 1-3%. For example: 1. xentop -b -d1 -i2, including last sample and I dismissed the rest of columns, for simplicity: NAME STATE CPU(sec) CPU(%) c5932 --b--- 6 0.0 c5964 --b--- 8 0.0 c6464 --b--- 7 0.0 deb7464 --b--- 6 0.0 Domain-0 -----r 1253 10.1 lobby --b--- 8 0.0 r5732 --b--- 238 1.5 r5764 --b--- 460 2.8 s10u8 --b--- 63 0.3 sdrcom --b--- 5 0.0 sdrorg --b--- 6 0.0 u100432 --b--- 4 0.0 u100464 --b--- 4 0.0 u120464 --b--- 6 0.0 win764 --b--- 340 2.3 2. mpstat: 04:59:56 PM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle 04:59:57 PM all 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 04:59:57 PM 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 04:59:57 PM 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 04:59:57 PM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle 04:59:58 PM all 0.00 0.00 0.52 0.00 0.00 0.00 0.00 0.00 99.48 04:59:58 PM 0 1.02 0.00 1.02 0.00 0.00 0.00 0.00 0.00 97.96 04:59:58 PM 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 So the 8-10% Im seeing all the time on dom0 reported by xentop seems to be xentop itself. Now, thats ok, but I dont understand why mpstat will not even close to xentop's CPU usage ? So why and how xentop gets the 10% usage ... !? If I increase the load on dom0 to 50% or 100% usage the measurements start to get closer. If I measure idle systems I always see a 10% difference no matter what ... I did execute both utilities same time for different periods of time, making sure they both run. Thanks a lot, -- Stefan Parvu <sparvu@systemdatarecorder.org> [1] - http://www.systemdatarecorder.org/recording/sysrec.html