How To Collect CPU MF Counters on z/VM
Starting with VM64961 for z/VM 5.4 and z/VM 6.1, z/VM can now collect and log out the System z CPU Measurement Facility host counters. These counters record the performance experience of the System z CEC on such metrics as instructions run, clock cycles used, and cache misses experienced. Analyzing the counters provides a view of the performance of the System z CPU and of the success of the memory cache in keeping the CPU from having to wait for memory fetches. The counters record other CPU-specific phenomena also.
To use the new z/VM CPU MF support, do the following:
- Run on System z hardware that includes the
CPU Measurement Facility. A z10 at driver 76D bundle 20 or
later, or any z196, or any z114 is all that is needed.
- Run z/VM 5.4 or z/VM 6.1 with VM64961 applied,
or run z/VM 6.2 or later.
- Authorize the z/VM partition to collect its
partition's counters. This is done at the System z
SE or HMC. The IBM red paper
Setting Up and Using the IBM System z CPU Measurement Facility with
describes this step. See section 2.2.2 therein for details.
Using the instructions provided in the red paper, enable
the basic counters,
the extended counters,
the crypto activity counters,
the problem state counters.
Configure CP Monitor to emit sample records in
the PROCESSOR domain. Most customers running Monitor already
configure CP Monitor in this way.
To check whether Monitor is already doing this, just issue
CP QUERY MONITOR
and look at the output to see whether
processor samples are enabled.
If they are not, place a
CP MONITOR SAMPLE ENABLE PROCESSOR command at the
spot in your startup automation that turns on Monitor.
This might be MONWRITE's PROFILE EXEC or PERFSVM's
PROFILE EXEC, for example.
Start recording MONWRITE data as you normally would.
- To check that everything's working, issue CP QUERY MONITOR. Look for processor samples to be enabled with the CPUMFC annotation appearing in the QUERY output. If you see NOCPUMFC, something's gone wrong. Check everything over, and if you can't figure it out, contact IBM for help.
Once these steps are accomplished, the new CPU MF sample records, D5 R13 MRPRCMFC, will appear in the Monitor data stream. MONWRITE will journal the new records to disk along with the rest of the Monitor records. Performance Toolkit for VM will not analyze the new records, but it won't be harmed by them either.
While it is not absolutely essential, it is very helpful for MONWRITE data containing D5 R13 MRPRCMFC records also to contain D5 R14 MRPRCTOP system topology records. The D5 R14 records report the placement of the z/VM partition's logical PUs onto CPU books and chips on the physical CEC. APAR VM64947 implements the D5 R14 records on z/VM 5.4 or z/VM 6.1.
IBM wants z/VM customers to contribute MONWRITE data containing CPU MF counters. These contributed MONWRITE files will help IBM to understand the stressors z/VM workloads tend to place on System z processors. For more information about how to contribute, use the "Contact z/VM" link on this web page.
To learn about how to interpret the collected data, visit our using CPU MF page.