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Monitoring core-utilization within guest LDOM

With Oracle VM Server 3.2 version new feature has been added to access CPU performance counters within Guest Logical Domains. With this feature one can run pgstat(1M) command inside the guest LDOM to monitor the hardware core utilization.

ldm (1M) command now has new option perf-counters=counter-set which needs to be enabled to access CPU performance counters within the guest LDOM.

With default installation primary LDOM (aka Control Domain) has access to the CPU performance counters (perf-counters) , one can verify with following command.

# ldm list -l primary |grep perf-counters
    perf-counters=global,htstrand

Note: Only one domain can have access to the performance counters, this is to prevent register overwrite. If you try to enable it in more than one domain, it would fail with the following error message.

# ldm set-domain perf-counters=global,htstrand ldgs11
Only one domain can have perf-counters set with global to prevent register overwrite.

If performance counter is not enabled within the guest domain, pgstat (1M) output would show has "0" for HW (Hardware Utilization) see the below output.

ldgs11@~# pgstat -v 1
PG  RELATIONSHIP                     HW UTIL  CAP     SW    USR    SYS   IDLE CPUS
 0  System                            -    -    -  12.8%  12.7%   0.1%  87.2% 0-15
 3   Data_Pipe_to_memory           0.0%    0 7.2B  12.8%  12.7%   0.1%  87.2% 0-15
 4    CPU_PM_Active_Power_Domain      -    -    -  12.8%  12.7%   0.1%  87.2% 0-15
 2     Floating_Point_Unit         0.0%    0 3.6B  12.5%  12.5%   0.0%  87.5% 0-7
 1      Integer_Pipeline           0.0%    0 7.2B  12.5%  12.5%   0.0%  87.5% 0-7
 6     Floating_Point_Unit         0.0%    0 3.6B  13.0%  12.9%   0.1%  87.0% 8-15
 5      Integer_Pipeline           0.0%    0 7.2B  13.0%  12.9%   0.1%  87.0% 8-15


Before setting perf-counters to guest domain. Unset the perf-counters from primary domain using following command.

 # ldm set-domain perf-counters= primary

Now add perf-counters to the guest domain 

 # ldm set-domain perf-counters=global,htstrand ldgs11

Note perf-counters will be available to the guest domain only after the reboot. Now run the same workload, one can see HW (Hardware Utilization) values being populated as part of pgstat(1M) output.

# pgstat -v 1
PG  RELATIONSHIP                     HW UTIL  CAP     SW    USR    SYS   IDLE CPUS
 0  System                            -    -    -  12.8%  12.7%   0.1%  87.2% 0-15
 3   Data_Pipe_to_memory           0.1% 9.8M 7.2B  12.8%  12.7%   0.1%  87.2% 0-15
 4    CPU_PM_Active_Power_Domain      -    -    -  12.8%  12.7%   0.1%  87.2% 0-15
 2     Floating_Point_Unit         1.7%  60M 3.6B  12.5%  12.5%   0.0%  87.5% 0-7
 1      Integer_Pipeline           7.5% 542M 7.2B  12.5%  12.5%   0.0%  87.5% 0-7
 6     Floating_Point_Unit         1.7%  60M 3.6B  13.0%  12.9%   0.1%  87.0% 8-15
 5      Integer_Pipeline           8.3% 597M 7.2B  13.0%  12.9%   0.1%  87.0% 8-15

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