[Xen-devel] xenoprof passive mode overhead

[Ya-Yunn Su <yayunn.su@xxxxxxxxx>]

Hi all,
  I'd like to use xenoprof passive mode on domain-0 to calculate L2
cache missed for each guest domain.  I setup oprofile daemon as
followed

opcontrol --start-daemon --event=LLC_MISSES:4000
--xen=/boot/xen-3.4.2.gz
--vmlinux=/scratch/xen-3.4.2/build-linux-2.6.18-lttng-xen0_x86_32/vmlinux
--passive-domains=1,2
--passive-images=/scratch/xen-3.4.0/build-linux-2.6.18-xenU_x86_32/vmlinux,/scratch/xen-3.4.0/build-linux-2.6.18-xenU_x86_32/vmlinux

My machine has two cores and I pinned domain-0 to one core and guest
domains to the other.  When I ran oprofile to calculate cache
misses/sec every 5 seconds on domain 0, I noticed that the transient
CPU utilization can be as high as 30%.  This affects the performance
of whatever benchmark I'm running in the guest domain.  Is this 30%
overhead for domain-0 common or am I doing something obviously wrong?
Any suggestion is appreciated.

Thank you,
Ya-Yunn

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