<div dir="ltr"><div>Hello.</div><div><br></div><div>I have been doing some performance tests with Xen and CentOS and have found some strange statistics when comparing the virtual memory (/proc/vmstat) and I/O (/proc/diskstat) statistics between the Domain 0 and guests. </div>
<div><br></div><div>When I look at the "pgpgin" statistic it is exactly the same as the "read sectors" in Dom0. However, when I look at the same statistics in the guest, the "read sectors" is exactly 2x "pgpgin".</div>
<div><br></div><div>I have tried this on 2 different versions, each on a different physical server. Here is an example of the statistics over a 30 second period (while running a benchmark in Dom1) in the Dom0 and Guest Domain.</div>
<div> pgpgin read sectors</div><div> ======= =========</div><div> Dom0 1698024 1698024</div><div> Dom1 848412 1696824</div><div><br></div>
<div>I have looked at some various settings to see if I could explain it. I can't tell if the Dom1 guest kernel is reporting incorrectly, or there is some other explanation. If anyone has any ideas about this I would appreciate any feedback.</div>
<div><br></div><div>Dom 0 kernels</div><div>3.10.29-11.el6.centos.alt.x86_64</div><div>3.4.54-8.el6.centos.alt.x86_64</div><div><br></div><div>Guest kernel</div><div>2.6.32-431.el6.x86_64</div><div><br></div><div>Thanks,</div>
<div><br></div><div>Deron</div></div>