Why CPU has been at 25%?

[vbox_test]

hosts: CPU:E8335 Memory:4G DDR2 800 HD:320G SATA2 MB:P43 type:Notebook OS:windows 8.1 X64 Graphic:ATI HD4650M

guset: Os:windows server 2003 R2 chip:ICH9 VM:vt-x Graphic:support 2D,3D

after install 4.3.10,I start the VM,When the client is loaded,the cpu of client has little rate.but the cpu of hosts has 25% rate above all the time.

[vbox_test]

ver:4.3.8

[vbox_test]

ver :4.3.10

[vbox_test]

the os of guest is 32bit

[Klaus Espenlaub]

The first log is spanning only a few seconds of VM run, but it clearly shows the same guest-related issue as the second. The second one has the following log line:

00:01:26.775126 RTC: period=0x20 (32) 1024 Hz 

which is effectively saying "start wasting CPU cycles by using a super high timer rate".

Shortly before the guest OS shutdown this is undone:

00:10:04.779198 RTC: period=0x200 (512) 64 Hz

Most likely you're running some application which requests this high timer rate (Microsoft advises against such high rates, as on real hardware it reduces the application performance and on laptop it reduces battery lifetime). In a VM this only gets worse, as interrupt delivery is significantly more expensive than on real hardware.

Try terminating applications manually until you see a line very similar to the 2nd one in VBox.log. It appears there with pretty much no delay after the application is terminated. Note that the log viewer in the GUI doesn't update automatically, it needs to be manually refreshed.

Additionally you have 2 VCPUs configured for the VM, which won't improve the situation, as VMs using SMP have a higher virtualization overhead unless the VCPUs are exclusively running code which needs no cross-CPU synchronization. So depending on the actual workload in the VM you might see anything from very small to very high additional overhead due to the 2nd VCPU. Try going back to one, it might improve the situation somewhat.

This is definitely a duplicate of the widespread "1kHz timer" problem, but I don't have time searching for other tickets talking about it.

[vbox_test]

Why the judge is different?

in 4.3.10: 00:00:01.173081 Guest OS type: 'Windows2003' 00:00:01.175152 fHMForced=true - SMP 00:00:01.175162 fHMForced=true - 64-bit guest

but in 4.3.8: 00:00:01.173081 Guest OS type: 'Windows2003' 00:00:01.175152 fHMForced=true - SMP

My guest is a 32-bit.

[aeichner]

Please reopen if still relevant with a recent VirtualBox release.