Using D3R2EC To Extract Encrypted Paging Metrics From Monitor
With z14 and z/VM APAR VM65993, z/VM can now encrypt guest pages to paging DASD. With this support, metrics were added to z/VM to help the z/VM system administrator understand how many pages are being encrypted and decrypted a second and the percent CPU being consumed for each task.
This article describes the new D3R2EC tool that reports on the new paging encryption information found in monitor record D3 R2 MRSTORSP. The article describes how to do the extraction and what the calculated metrics mean.
How to Collect the Data
To collect the data, run CP Monitor with processor domain samples enabled. The encrypted paging performance information lands in the D3 R2 monitor records. To make a recording of the monitor records, run MONWRITE. If you need help running MONWRITE, refer to this article.
How to Reduce the Data
Once you have a MONWRITE file, you can use the D3R2EC tool to obtain the metrics in a human-readable format. The process amounts to this:
- Start with a MONWRITE file that contains D3 R2 records.
- Run the D3R2EC tool against the MONWRITE file. The D3R2EC takes the MONWRITE file as input and produces the report file as output. The report file will have CMS filetype $D3R2EC.
Appearance of the $D3R2EC Report
The encrypted paging metrics describe the rate of 4 KB pages encrypted and decrypted by each logical processor and the percent CPU used to accomplish these tasks by each logical processor over time. The resulting tabular report bears a vague resemblance to a Performance Toolkit By-Time report.
Here is an excerpt of an encrypted paging report. The report is wide; on this web page, for page rendering purposes, we have broken the columns into groups.
The workload here was entirely contrived for internal lab purposes; the values in the report mean absolutely nothing as far as customer workload expectations are concerned.
The report consists of the rate of pages encrypted and decrypted by each logical processor and the percent CPU used by each logical processor.
The table below gives definitions for each of the columns in the report.
|Encrypted Paging Statistics|
The hh:mm:ss of the CP Monitor interval-end time, in UTC.
The first block of rows is marked ">>Mean>>" to indicate that the rows are the mean of the logical processors over the monitor interval.
The first ">>Total>" row indicates the sum of logical processor ">>Mean>>" values combined over the monitor interval.
The subsequent rows marked ">>Total>" indicates the sum of logical processor values combined over the interval.
|Type||The logical processor type: CP, IFL, etc.|
|LPU||Logical processor number.|
|Rate of Pages Enc+Dec||Sum of the rate of 4 KB pages encrypted and decrypted by each logical processor for the monitor interval.|
|Rate of Pages Encrypted||Rate of 4 KB pages encrypted by each logical processor for the monitor interval.|
|Rate of Pages Decrypted||Rate of 4 KB pages decrypted by each logical processor for the monitor interval.|
|Percent CPU busy Enc+Dec||The sum of percent CPU used by each logical processor to encrypt and decrypt the pages for the monitor interval.|
|Percent CPU busy Encrypt||Percent CPU used by each logical processor to encrypt the pages for the monitor interval.|
|Percent CPU busy Decrypt||Percent CPU used by each logical processor to decrypt the pages for the monitor interval.|