Hardware performance events are not counted by "perf" in a 2.6.31.12 KVM guest

Hardware performance events are not counted by "perf" in a 2.6.31.12 KVM guest

[Naresh Rapolu]

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.

Re: Hardware performance events are not counted by "perf" in a 2.6.31.12 KVM guest

[Chris Wright]

* Naresh Rapolu (nrapolu@purdue.edu) wrote:
> "perf"  tool does not count  hardware performance events ( cache misses  
> etc) in a  KVM guest

The guest does not see a PMU.  For basic profiling you can use timer
based in guest, but there is not yet support for PMU.

thanks,
-chris