#159 Timer of guest is inaccurate

[yunfeng]

I tried to build kernel on a linux guest with 2 vcpus, and measured the time by both guest timer and network timer.
The result is guest timer lower than network timer by 30% after about 3 minutes.

The time cost of the kernel build:
Guest timer: 181s
Network timer: 137s

[yunfeng]

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Here are some new test results for guest timer

On rhel5 UP guest with 1G memory
Realtime 3min
Guesttime 21s

On rhel5 guest with 4vcpus with 1G memory:
Realtime 3min
Guest 28s

On 32e rhel4 UP guest and run workload
Realtime 3min
Guest 3min

On IA32e RHEL4 guest with
Realtime 3min
Guest 3min15s

[karmapolis]

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Also affects Windows XP guests. This bug wasn't present in kvm-35 but appeared shortly after that.

[karmapolis]

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Also happens with only one vcpu.

[yunfeng]

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on IA32e RHEL5 guest the timer is about 5x faster than network timer!
If measure kernel build with both guest timer and network timer, data collected by guest timer is 55s but by network timer it's 281s.

[stevie1024]

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I filed a new bug (1900228) that I think is a more general bug description that causes this bug's behaviour.

[yunfeng]

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This issue has been fixed after patches of kernel pit were checked in.