Xen users - Aug 2011 - Why the data got from "top" and "xentop" are different?

Hi All,

I''m a beginner in Xen. Recently I''ve configured one VM (vm03)
hosted in my
physical machine. I ran the "netperf" workload in the vm01, and used
the
"top" command in the vm03 to test the behavior of the running
workload.
Meanwhile, I also used the "xentop" command in domain0 to see the
resource
consumption in vm03. Interestingly, I found that the CPU usage data is
extremely different with each other. The CPU usage data in "xentop"
was
13.6%, while in "top" the data was only 1.0%.

So why does this happen?

Xentop detail data:
2 domains: 2 running, 0 blocked, 0 paused, 0 crashed, 0 dying, 0 shutdown
Mem: 25099756k total, 20868028k used, 4231728k free    CPUs: 16 @ 2400MHz
      NAME  STATE   CPU(sec) CPU(%)     MEM(k) MEM(%)  MAXMEM(k) MAXMEM(%)
VCPUS NETS NETTX(k) NETRX(k) VBDS   VBD_OO   VBD_RD   VBD_WR SSID
  Domain-0 -----r        822   38.9   16314368   65.0   no limit
n/a    16    0        0        0    0        0        0        0    0
      vm03 -----r         77   13.6    4193024   16.7    4194304
16.7     4    1 12177577    73198    1        0    68043    37282    0

Top detail data:
Tasks: 123 total,   2 running, 121 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us,  0.1%sy,  0.0%ni, 99.8%id,  0.0%wa,  0.0%hi,  0.1%si,
0.1%st
Mem:   4193204k total,  2073200k used,  2120004k free,   117796k buffers
Swap:        0k total,        0k used,        0k free,  1652528k cached
  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+
COMMAND
 3175 root      15   0  9108  980  624 R  1.0  0.0   0:00.04
netperf
    1 root      15   0 10352  684  576 S  0.0  0.0   0:00.01
init
    2 root      RT   0     0    0    0 S  0.0  0.0   0:00.00
migration/0
    3 root      34  19     0    0    0 S  0.0  0.0   0:00.00
ksoftirqd/0
    4 root      RT   0     0    0    0 S  0.0  0.0   0:00.00
watchdog/0
    5 root      10  -5     0    0    0 S  0.0  0.0   0:00.00
events/0
    6 root      10  -5     0    0    0 S  0.0  0.0   0:00.00
khelper
    7 root      10  -5     0    0    0 S  0.0  0.0   0:00.00
kthread
    9 root      17  -5     0    0    0 S  0.0  0.0   0:00.00
xenwatch
   10 root      10  -5     0    0    0 S  0.0  0.0   0:00.00
xenbus
   14 root      RT  -5     0    0    0 S  0.0  0.0   0:00.00
migration/1
   15 root      34  19     0    0    0 S  0.0  0.0   0:00.00
ksoftirqd/1
   16 root      RT  -5     0    0    0 S  0.0  0.0   0:00.00
watchdog/1
   17 root      10  -5     0    0    0 S  0.0  0.0   0:00.00
events/1
   18 root      RT  -5     0    0    0 S  0.0  0.0   0:00.00
migration/2
   19 root      34  19     0    0    0 S  0.0  0.0   0:00.00
ksoftirqd/2
   20 root      RT  -5     0    0    0 S  0.0  0.0   0:00.00 watchdog/2

My Xen version is 3.3.1.

*Best Regards,*
*Faye*


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On Tue, Aug 30, 2011 at 9:14 AM, 徐飞 <kudofaye@gmail.com>
wrote:
> Hi All,
>
> I''m a beginner in Xen. Recently I''ve configured one VM
(vm03) hosted in my
> physical machine. I ran the "netperf" workload in the vm01, and
used the
> "top" command in the vm03 to test the behavior of the running
workload.
> Meanwhile, I also used the "xentop" command in domain0 to see the
resource
> consumption in vm03. Interestingly, I found that the CPU usage data is
> extremely different with each other. The CPU usage data in
"xentop" was
> 13.6%, while in "top" the data was only 1.0%.
>
> So why does this happen?
>
This is a common question:
http://lists.xensource.com/archives/html/xen-users/2008-10/msg00415.html

You may want to look into the profile tools for Xen if you need better
granularity.

See for example:

http://xenoprof.sourceforge.net/

Hope that helps.

Thanks,
Todd


-- 
Todd Deshane
http://www.linkedin.com/in/deshantm
http://www.xen.org/products/cloudxen.html
http://runningxen.com/

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