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Performance Management

These changes affect the performance management of z/VM and TCP/IP VM.

  • Monitor Enhancements
  • Effects on Accounting Data
  • VM Performance Products

Monitor Enhancements

There were five areas of enhancements affecting the monitor data for z/VM 4.4.0. Changes were made to both system configuration information and to improve areas of data collection. As a result of these changes, there is one new monitor record and several changed records. The detailed monitor record layouts are found on our control blocks page.

In systems with large numbers of LPARs and logical CPUs (The current limit for a 16-way is 158 logical CPUs.), the potential existed for LPAR information data to be truncated. Support was added to the monitor to correctly reflect the number of LPARs and their associated logical CPUs. In addition, a field was added to identify the type of logical CPU for which data is being reported. The Domain 0 Record 15 (Logical CPU Utilization Data) and the Domain 0 Record 16 (CPU Utilization Data in a Logical Partition) records were updated for this support.

Domain 0 Record 20 (Extended Channel Measurement Data) was updated to better reflect the information returned when the Extended Channel Measurement facility is enabled. Documentation was added to further define the contents and format of the channel measurement group dependent channel-measurements characteristics and the contents and format of the channel utilization entries.

The Extended-I/O-Measurement facility (available on the z990 processor) was updated to add support for the format-1 subchannel measurement blocks (SCMBKS). The size of the format-1 SCMBKS has increased, including fields within the SCMBKS which are now fullword versus halfword fields. The format-1 SCMBKS are now dynamically allocated. The updated records include: Domain 0 Record 3 (Real Storage Data), Domain 1 Record 4 (System Configuration Data), Domain 1 Record 7 (Memory Configuration Data), Domain 3 Record 4 (Auxiliary Storage Management), Domain 3 Record 11 (Auxiliary Shared Storage Management), Domain 6 Record 3 (Device Activity) and Domain 6 Record 14 (Real Storage Data).

A new record, Domain 6 Record 21 (Virtual Switch Activity), was added to provide data for I/O activities for a virtual switch connection to a real hardware LAN segment through an OSA Direct Express. The information in this record is collected for the data device associated with an OSA in use by a virtual switch.

To improve performance by increasing guest throughput when CP is running in a multiprocessing environment, the timer request block management was removed from the scheduler lock and a new lock was created to serialize that function. Prior to this change, the scheduler lock was used to handle the serialization of scheduler activities, handle timer request block management, and handle processor local dispatch management. Since the timer request block management is no longer a part of the scheduler lock, two new fields have been added to Domain 0 Record 10 (Scheduler Activity) to provide data specific to the timer request block management scheduler activity.

Additionally it must be noted that starting with the z990 processor, the STORE CHANNEL PATH STATUS instruction used to create the Domain 0 Record 9 (Physical Channel Path Contention Data) monitor record will no longer return valid information. Please refer to Domain 0 Record 20 (Extended Channel Measurement Data) for valid channel path utilization data.

Effects on Accounting Data

When using z/VM Virtual Switch, CP time is charged to the VM TCP/IP controller virtual machine while handling interrupts. Once the datagrams have been queued to the receiving stack and receive processing starts, CP time is charged to the receiving stack virtual machine. The reverse is true for the send case. While CP is extracting segments from the stack's buffers, the time is charged to the sending stack. At this point the buffers are given to the OSA-Express card and no further time is charged. See z/VM Virtual Switch for further information about the virtual switch.

None of the other z/VM 4.4.0 performance changes are expected to have a significant effect on the values reported in the virtual machine resource usage accounting record.

VM Performance Products

This section contains information on the support for z/VM 4.4.0 provided by the Performance Toolkit for VM, VMPRF, RTM, and VMPAF. As noted in our May 13 announcement, it is planned that future performance management enhancements will be made primarily to the Performance Toolkit for VM. z/VM V4.4 is planned to be the last release in which the RTM and PRF features will be available.

The Performance Toolkit for VM provides enhanced capabilities for a z/VM systems programmer, operator, or performance analyst to monitor and report performance data. The toolkit is an optional, per-engine-priced feature derived from the FCON/ESA program (5788-LGA), providing:

  • Full-screen mode system console operation and management of multiple z/VM systems

  • Post-processing of Performance Toolkit for VM history files and of VM monitor data captured by the MONWRITE utility

  • Viewing of performance monitor data using either web browsers or PC-based 3270 emulator graphics

  • TCP/IP performance reporting

  • Viewing of Linux performance data obtained from the Resource Management Facility (RMFTM) Linux performance gatherer, rmfpms.

On the Performance Toolkit page you will find links to files that cross reference RTM and VMPRF functions to similar functions and reports of the Performance Toolkit for VM.

VMPRF support for z/VM 4.4.0 is provided by VMPRF Function Level 4.1.0, which is a preinstalled, priced feature of z/VM 4.4.0. VMPRF 4.1.0 can also be used to reduce CP monitor data obtained from any supported VM release. The latest service is required.

RTM support for z/VM 4.4.0 is provided by Real Time Monitor Function Level 4.1.0. As with VMPRF, RTM is a preinstalled, priced feature of z/VM 4.4.0. The latest service is required and is pre-installed on z/VM 4.4.0

Performance Analysis Facility/VM 1.1.3 (VMPAF) will run on z/VM 4.4.0 with the same support as for z/VM 4.3.0.

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