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Performance Improvements

Large Enhancements

With the change to continuous delivery, IBM has shipped most of the recent new z/VM function as PTFs to z/VM 7.1 instead of waiting for a release boundary. We evaluated some of those PTFs and wrote articles about them. For more information, refer to our z/VM 7.1 page.

Some z/VM 7.1 PTFs providing performance or capacity improvement were not evaluated for this report. Those were:

PI99085: z/VM TCP/IP support for the OSA Express7S card.

VM65786: Remove limit of number of users who can belong to a resource pool.

VM66248: Support the z15 and LinuxONE III processors.

VM66263: Support EAV ECKD volumes.

VM66283: Support System Recovery Boost.

Small Enhancements

In our considerations chapter we mentioned some changes clients might like to consider before they migrate to z/VM 7.2. For details, refer to that chapter.

Service Since z/VM 7.1

z/VM 7.2 contains a number of performance-related repairs that were first shipped as service to earlier releases. Because IBM refreshes this report only occasionally, IBM has not yet had a chance to mention these PTFs.

VM65686: Perfkit will sometimes show impossibly high percent-busy in FCX100.

VM66154: Enforce ABSOLUTE LIMITHARD correctly. Note: this went PE. Also apply VM66400.

VM65730: Improve performance of SET RDEV commands that specify large ranges of device numbers.

VM66282: Fix unduly long wait for an EDEV to vary on.

VM65858: Improve respect of relative share for guests in a CPU pool.

VM66302: Streamline vswitch interruption processing.

Miscellaneous Repairs

IBM continually improves z/VM in response to customer-reported or IBM-reported defects or suggestions. In z/VM 7.2 the following small improvements or repairs are notable:

Excessive host Diag x'9C's: HCPHVR now avoids SIGP Sense Running and Diag x'9C' if the target logical processor is a vertical-high.

Excessive recursion: Removes excessive recursion in the SCSI container with respect to the deferred work queue.

VSwitch performance: Better management of opening of dispatch window.

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