libvirt users - Jul 2015 - Re: virsh dominfo does not show correct cpuTime

I was getting vCPU use time outside of guest with libvirt-python API, and
them calculate utilization with (cpuTime2 - cpuTime1) / (t2 - t1). I was
not doing this inside the guest os.

2015-07-24 15:09 GMT+08:00 2020human <human2020@qq.com>:
> You calculate is vCPU use time not utilization。
>
> use_time/total_cpu_time  is utilization。
>
> total_cpu_time=`cat /proc/stat |sed -n '1p'|awk '{ print
> sum=$2+$3+$4+$5+$6+$7+$8+$9+$10}'`
>
>
> ------------------ 原始邮件 ------------------
> *发件人:* "changqian zuo";<zuochangqian@gmail.com>;
> *发送时间:* 2015年7月24日(星期五) 中午1:51
> *收件人:* "libvirt-users"<libvirt-users@redhat.com>;
> *主题:* [libvirt-users] virsh dominfo does not show correct cpuTime
>
> Hi,
>
> I am doing some domain resource monitoring work. I use
>
>   cat /dev/urandom | md5sum
>
> to simulate vCPU load and write a script to calculate vCPU utilization. It
> seems all good at the beginning. After I abort the ``cat ... md5sum``
> command in domain, I see some strange data as below:
>
> CPU time: 8410960000000
> CPU util: 99.8410609331%
> CPU time: 8411970000000
> CPU util: 100.843672381%
> CPU time: 8412380000000
> CPU util: 40.9336949531%
> CPU time: 8412440000000
> CPU util: 5.9899303915%
> *CPU time: 8412440000000*
> *CPU util: 0.0%*
> CPU time: 8412490000000
> CPU util: 4.99165856007%
> *CPU time: 8412490000000*
> *CPU util: 0.0%*
> *CPU time: 8412490000000*
> *CPU util: 0.0%*
> CPU time: 8412570000000
> CPU util: 7.987195515%
> *CPU time: 8412570000000*
> *CPU util: 0.0%*
> CPU time: 8412590000000
> CPU util: 1.99668576091%
> CPU time: 8412670000000
> CPU util: 7.98700539474%
> CPU time: 8412720000000
> CPU util: 4.99167281754%
> CPU time: 8412780000000
> CPU util: 5.98888552548%
>
> Looking at those 0.0% lines. Strange, though the guest is running, cpuTime
> does not increase. How can this happen? Any one helps? Thanks.
>
> Host information:
>
> - CentOS Linux release 7.0.1406 (Core)
> - libvirt 1.2.8
> - qemu-kvm-rhev 2.1.2
>
> ----- python script to capture cpu domain usage ----
> import libvirt
> import time
>
> conn = libvirt.openReadOnly("qemu:///system")
> dom = conn.lookupByName('cpu-test')
> last_time = time.time()
> last_cpu_time = dom.info()[4]
>
> while True:
>   time.sleep(1)
>   this_time = time.time()
>   dom_info = dom.info()
>
>   print "CPU time: %s" % dom_info[4]
>   print "CPU util: %s%%" % ((dom_info[4] - last_cpu_time) /
((this_time -
> last_time) * 10000000))
>
>   last_cpu_time = dom_info[4]
>   last_time = this_time
> ----------------------------- end -----------------------------
>
>
>