I have a cloud dynamic server that I rent from 1and1 running Windows Server 2012 Standard. A few days ago, the system interrupt process started using a large amount of CPU (20-80% while idle). I contacted 1and1 support and was told it was a problem with inconsistencies in my VM, specifically when interacting with their Citrix Xen Manager. They installed Citrix Xen Windows Guest Agent, and it appears to be mitigating this issue decently (CPU usage for this now runs anywhere between 5-15% while idle.
This number still seems high to me though. I'm no expert in this type of thing, but surely there's a way to bring that down so that it's consistently below 10% if the server is idle. I understand it'd be higher if the server were actively preforming tasks, but if it's just idle I can't see a reason why it'd be that high.
Are there some Windows tweaks I can implement to help with this issue?
Best Answer
"Inconsistencies in your VM" sounds like BS from your hosting provider.
The hardware in your computer, such as a clock, or a network card, or disk drive, or a keyboard, all need to communicate with the CPU. They do this through interrupts, regardless of if it's a physical machine or a VM. When a device interrupts the CPU, the CPU runs whatever interrupt handling code is registered for that device, and that code takes up CPU cycles.
When you see a high volume of interrupts, and you're just sitting there idling, not doing anything... it's usually a sign of bad, misconfigured and/or misbehaving device drivers. This is often exacerbated in virtualization scenarios, as the hypervisor tries to emulate and synthesize devices in a way that's still compatible with the operating system.
Installing the 'Guest Agent,' or integration tools as they also known, was definitely a step in the right direction. You always want to have the integration tools installed on your VM regardless of the guest OS or the hypervisor. These integration tools give the virtualized operating system what it needs to play nice with the hypervisor.
But without a more detailed analysis with performance and debugging tools, there may not be anything else you can do. What version of Xen are they running? Is it a version that is even compatible with Server 2012 as a guest OS?
You mention that it was working alright up until a few days ago. What happened a few days ago? Was a patch installed? Did your hosting provider perform maintenance? Do your event logs say anything from around the time of the performance degradation?