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SubjectHardware performance events are not counted by "perf" in a 2.6.31.12 KVM guest
Hello,

"perf" tool does not count hardware performance events ( cache misses
etc) in a KVM guest ( Ubuntu 9.10 karmic, 2.6.31-14-generic kernel)
on Xeon 5530 quad-core. The host is 2.6.28 kernel , Ubuntu 8.04
LTS, Hardy.

readfile.sh reads in a large file (1430 lines), which should cause
cache-misses.
root@multicore4-vm3:/usr/src/linux-2.6.31.12/tools/perf# ./perf stat -r
5 -- bash readfile.sh

Performance counter stats for 'bash readfile.sh' (5 runs):

11002.207467 task-clock-msecs # 1.042 CPUs ( +-
10.834% )
3480 context-switches # 0.000 M/sec (
+- 19.017% )
2238 CPU-migrations # 0.000 M/sec (
+- 29.488% )
482299 page-faults # 0.044 M/sec (
+- 0.141% )
0 cycles # 0.000
M/sec ( +- nan% )
0 instructions # nan
IPC ( +- nan% )
0 cache-references # 0.000 M/sec (
+- nan% )
0 cache-misses # 0.000 M/sec (
+- nan% )

10.560510393 seconds time elapsed ( +- 11.401% )

Do I need to make some configuration changes to enable hardware events
? A similar question was posted recently here :
http://lkml.org/lkml/2010/3/18/342 but no response !
Any help would be greatly appreciated.

Thanks,
Naresh Rapolu.


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