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RE: [Xen-users] Re: xentop CPU Usage

  • To: <kyrios@xxxxxxxxx>
  • From: "Fischer, Anna" <anna.fischer@xxxxxx>
  • Date: Wed, 5 Sep 2007 20:35:23 +0100
  • Cc: xen-users@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Wed, 05 Sep 2007 12:36:09 -0700
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Thread-index: Acfv0vTUlvwNSEJkQh+8QV6TjM15jAAAdTSw
  • Thread-topic: [Xen-users] Re: xentop CPU Usage

On a SMP system this normally means that you use 300% out of 800%.
However, note that as far as I understand, Xentop shows "virtual" CPU (VCPU) usage. So the numbers will vary depending on how you have configured your DomU with VCPUs and how these run on actual physical CPUs. For example, if you run two domains which are configured with a single VCPU each, then it might be that Xentop shows 100% CPU usage for both domains if they run on different physical CPUs, but only up to 50% each if they run on the same physical CPU. You can see the assignment of physical CPUs with the xm vcpu-list command.
Also, I would recommend to use XenMon for measuring CPU utilization on a Xen system. Have a look at this:

From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Kyrios
Sent: 05 September 2007 12:53
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Re: xentop CPU Usage

Hi again list,

does anyone know something about this topic?

We have 4 hosts with 8 CPU Cores each. We have some performance problems and don't know if it is a CPU Utilization problem. For example one of the hosts has (accumulated) 300% CPU usage in Xentop (xm top). Does this mean it's 3 times to much or does it mean it uses 300% of 800% available?


On 7/15/07, Kyrios <kyrios@xxxxxxxxx> wrote:
Hi list,

when xentop says cpu Usage für domU ist 20% what does that exactly mean on a multi cpu machine. Does it mean that one of the CPUs is used by 20% or does it mean the domU uses 20% off all available CPU time?


... black holes are where god divided by zero.

... black holes are where god divided by zero.
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