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[Xen-users] Gathering "metal" stats

  • To: xen-users@xxxxxxxxxxxxxxxxxxx
  • From: Tyler Szabo <tyler.szabo@xxxxxxxxx>
  • Date: Thu, 11 Jun 2009 14:22:14 -0700
  • Delivery-date: Mon, 15 Jun 2009 02:57:48 -0700
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  • List-id: Xen user discussion <xen-users.lists.xensource.com>

Hey All,

Iâm attempting to gather stats on usage of the âmetalâ, by which I mean the physical hostâs hardware. I would like to know the CPU, IO, and network stats for the hardware.

Normally I would get these from /proc/stat, /proc/diskstat, and ifconfig respectively. However, because of the segregation of VMs and Dom0âs special relationship as a paravirtualized I donât know if I can trust this data.

Iâm aware that /proc/stat is unusable as Dom0 will not see cycles that DomUs are stealing, and thus it does not give me accurate utilization of the metal â I know that I can calculate the actual CPU usage of each VM using âvm list âlongâ and comparing cpu_time to uptime, so thatâs not a problem.
The issue arises when I attempt to get IO stats â DomUs see their own âsda1â (or whichever) â I donât know if this means that the âsdaâ that Dom0 sees is the real hardware or an abstraction. The question I have is: do IO operations on DomUs result in IO operations on Dom0âs âsdaâ such that /proc/diskstat sees it? Or is that hidden from Dom0 like DomU CPU usage?
Similarly with network stats: Iâm sure that Dom0âs eth0 does not report network traffic that DomUs used, but does peth0 report traffic that âhit the wireâ? Additionally, does this include traffic that occurs between Dom0 and DomU, that doesnât escape into the network substrate?

Iâm testing this myself as I write this, but Iâd rather have my âresearchâ confirmed by knowledgeable users.

Thanks all,
-Tyler Szabo
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