[Xen-devel] measuring cpu utilization under i/o workload

[tim benke <tbenke@xxxxxxxxxxxx>]

Hello,

I run I/O-bound experiments and I would like to measure CPU utilizations in Dom0 and DomU. Though these experiments were only executed in Dom0 to find out which tool reports consistent numbers.

Xentop reports much higher utilization when compared to mpstat or top in a xen-capable kernel. 

In a kernel without xen mpstat reports higher utilizations but still not comparable to xentop (See attached summary of the data).

My question is: which tool is actually correctly reporting how much the physical CPUs are used?

My test system is:

OpenSuSE 10.3

Xen 3.1

default OpenSuSE kernels version 2.6.22

2 AMD dual-core 2212 HE CPUs at 2 GHz

10 GB RAM

hard drive is a IBM-ESXS ST936701SS 71GB

experiment:

commands executed: 

# flush cache (pagecache, dentries and inodes (see http://linux-mm.org/Drop_Caches))

echo 3 > /proc/sys/vm/drop_caches;

# start measurements, time copying of a file, stop measurements

# measurements were taken at 5 second intervals

time cp random_1000M.bin random2.bin;

# delete file

rm random2.bin

space-aligned in monospace font:

xen domain 0

with xen-kernel: runtime ~= 36-38 seconds

xentop:              0.0,    18.3,   13.8,   13.8,   13.5,   12.2,   12.1,

mpstat-sys:          0.15,   0.15,   0.20,   0.48,   0.16,   0.15,   0.90,

mpstat-user:         0,      0,      0,      0,      0,      0,      0,  

mpstat-iowait:       25.84,  24.84,  24.85,  23.75,  25.75,  24.88,  29.55

top-sys:             0.1,    0.1,    0.1,    0.8,    0.1,    0.4,    0.2,    0.4,

top-user:            0.0,    0.0,    0.0,    0.0,    0.0,    0.0,    0.0,    0.0,

kernel without xen: runtime ~= 33-38 seconds

mpstat-sys:              4.24,   2.5,    2.85,   3.05,   2.8,    3.15,   3.54,

mpstat-user:             0.05,   0,      0,      0,      0.05,   0.05,   0.0,

mpstat-iowait:           20.67,  31.87,  37.86,  42.06,  47.13,  33.05,  25.56

top-sys:        2.0,     4.4,    3.2,    1.7,    2.8,    3.1,    2.9,    2.2,    

top-user:       0.4,     0.0,    0.0,    0.0,    0.0,    0.0,    0.0,    0.0

thanks,

..Tim

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel