[Xen-bugs] [Bug 717] hdparm reports much slower cached I/O in dom0/domU than on native OS

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http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=717





------- Comment #2 from inakoshi.hiroya@xxxxxxxxxxxxxx  2006-10-24 04:59 -------
In the previous report, the vcpu configuration was:
dom0: #vcpu=1, pinned on pcpu#0
domU: #vcpu=1, any cpu (e.e.

Comparison was not fair.  I would report the case where the domU vcpu is pinned
so that a pcpu is dedicated to it.  In addition, I added standard deviations
over each 10 runs.

The conclusion was;

1/ considering the efficient buffered I/O ratio and the large standard
deviation of cached I/O throughput, we can say that the performance was almost
ideal in the latest C/S, meaning that cached I/O ratio was similar to buffered
I/O ratio.
2/ There was no significant difference between the results with and without
vcpu-pin.  I confirmed this by t-test with 5% significance level.


Results:

Xen   : ia64-unstable C/S 11810
Native: rhel4u4
Xen0  : linux-2.6.16.29-xen
XenU  : linux-2.6.16.29-xen

o hdparam -tT /dev/sda
Value Format:
  mean+/-stdev (normalized by native throughput)

buffered IO: native                      93.29+/-0.05
             dom0                        92.96+/-0.62    (0.99)
             domU (without vcpu-pin)     92.74+/-0.92    (0.99)
             domU (with vcpu-pin)        91.78+/-2.50    (0.98)
cached IO:   native                    5959.69+/-1897.60
             dom0                      5481.48+/- 722.56 (0.91)
             domU (without vcpu-pin)   5037.76+/- 597.84 (0.85)
             domU (with vcpu-pin)      5788.94+/- 788.11 (0.97)


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