On Sat, 2012-12-08 at 06:48 +0100, Zoltan Frombach wrote:
I've also heard that older versions of Windows don't put the CPU to "idle mode" even when there is nothing to do. It is a known problem with older Windows kernels.
Windows is installed without ACPI, this way the CPU does not get IDLE instructions and Windows uses all vCPU time it can get. I don't know why ACPI is deactivated by default - some say performance without ACPI is higher, some say because of compatibility - anyway you have to choose between high load of host machine's CPU at ALL time or the best performance of Windows virtual machine when under load.
My choice is to enable ACPI on windows virtual machines and the problem is solved.
#virsh edit WinXP .... <features> <acpi/> <apic/> <pae/> </features> ....
You should have <acpi/> in <features>. If you don't - add it.
Another way to add it is to open virtual machine manager (virt-manager), open virtual machine there, go to 'details' (button with blue 'i' on it), look in 'overview' screen, open 'Machine Settings', mark 'enable ACPI' there.
Best regards, Dmitry Mikhailov.
Anyway, try to install the latest virtio drivers for Windows if you don't already have.
On 12/7/2012 9:18 PM, Robert Dinse wrote:
About the only thing you can do is not run Windows, or at least thatversion, XP does the same thing, continuouslys spins the CPU when there aren't any user processes using time. I've heard this is resolved in Windows-7 but haven't tried it personally.
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On Fri, 7 Dec 2012, Shawn Everett wrote:
Date: Fri, 7 Dec 2012 12:02:14 -0800 From: Shawn Everett shawn@tandac.com Reply-To: Discussion about the virtualization on CentOS
<centos-virt@centos.org>To: centos-virt@centos.org Subject: [CentOS-virt] (no subject)
Hi All,
I have recently installed CentOS 6.3 with QEMU+KVM for Virtualization.
I have successfully created a Windows 2003 VM with 4GB of RAM. The host server is an HP ML350 G8 with 24GB RAM and 24 cores. Details of one of the cores is shown below:
processor : 23 vendor_id : GenuineIntel cpu family : 6 model : 45 model name : Intel(R) Xeon(R) CPU E5-2620 0 @ 2.00GHz stepping : 7 cpu MHz : 1200.000 cache size : 15360 KB physical id : 1 siblings : 12 core id : 5 cpu cores : 6 apicid : 43 initial apicid : 43 fpu : yes fpu_exception : yes cpuid level : 13 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 x2apic popcnt aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid bogomips : 3989.86 clflush size : 64 cache_alignment : 64 address sizes : 46 bits physical, 48 bits virtual power management:
On an otherwise completely idle system I've noticed the load to be 1.0 to 1.5 range. Running "top" shows the culprit to be: qemu-kvm.
Is this normal behavior? I would have expected the load to be pretty light.
Stopping the VM restores the load to normal once again.
Is there anything I can do to reduce the load?
Shawn
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