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