performance question

[david ahern <daahern@cisco.com>]

I am trying to understand spikes in system time that I am seeing in a VM. The
guest OS is RHEL4, with 2 vpcus, and 2.5Gb RAM; host is running 2.6.24.2 kernel.
kvm version is kvm-63.

Using the stat scripts Christian Ehrhardt posted a few days ago (thanks,
Christian, very handy tool) I collected kvm_stat data as a function of time (I
added time to the output). Comparing plots of guest system time to plots of
kvm_stat the spikes in system time most correlate to the following kvm_stat
variables:

mmu_cache_miss
mmu_flooded
mmu_pte_updated
mmu_pte_write
mmu_shadow_zapped
pf_fixed
pf_guest
remote_tlb_flush
tlb_flush

Can someone provide some guidance/hints on what would cause spikes in the above
and if there is anything I can do to improve it?

The load on the VM is fairly constant (network traffic of ~48kB/sec received and
 ~189kB/sec transmit) with some moderate disk IO as well.

thanks,
david

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