Performance Improvements
Large Enhancements
In Summary of Key Findings this report gives capsule summaries of the performance notables in z/VM 7.1.
Small Enhancements
z/VM 7.1 contains several small functional enhancements related to performance. These were shipped as SPEs on top of z/VM 6.4. In the noted cases, there is an accompanying chapter in this report.
PI72106: TCP/IP SSL exploit CRYPTO APVIRT. See the article.
PI73016: TCP/IP exploit OSA Express6S.
VM65846: Can help reduce the need to intercept out of SIE to enforce a guest's virtual architecture level.
VM65929: Support concurrent I/O on XIV EDEVs. See the article.
VM65942: Support for z14. Includes per-VCPU privileged operation tracking in Monitor. (Went PE: also apply VM66071)
VM65987: Lets guests use the Guarded Storage Facility. This can improve performance of Java heap management.
VM65988: Improvements to CP spin lock manager.
VM65989: CP dump enhancements. See the article.
VM66026: Monitor enhancements for zHPF.
VM66063: New unparking heuristics can decrease PR/SM overhead. See the article.
VM66090: Improves performance of simulation of I/O to PCI functions.
VM66095: Improve Monitor for FCP chpids and devices. See the article.
VM66098: Support Extent-Space-Efficient storage.
Service Since z/VM 6.4
z/VM 7.1 also contains a number of performance 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.
VM65644: Certain EDEV monitor fields were not being filled in.
VM65741: Make all 3390-A DASD eligible for MDC.
VM65885: Perfkit needs deprecated HPF monitor fields.
VM65886: Make minidisk I/O eligible for HyperPAV aliases.
VM65916: Repairs lost initiative on HiperSockets guest LANs.
VM65946: Improves speed of SECUSER console output.
VM65979: Remove unnecessary MDC purge done during HyperSwap.
VM65992: Improves speed of dedicated HiperSocket adapter.
VM65998: Reduce polling frequency for crypto adapters.
VM66026: Monitor enhancements for HyperPAV and PAV aliases. (Went PE: also apply VM66036)
Miscellaneous Repairs
IBM continually improves z/VM in response to customer-reported or IBM-reported defects or suggestions. In z/VM 7.1 the following small improvements or repairs are notable:
Relative max-share: The arithmetic for calculating the entitlement associated with a relative max-share was wrong. The arithmetic was repaired.
Cache behavior: In virtual networking, certain control blocks were reorganized to reduce cache contention.
VSwitch load balancing: The VSwitch load balancing algorithm was improved.
CP use of Diag x'9C': CP no longer issues unnecessary or ill-advised Diag x'9C's to PR/SM.
Skipped monitor intervals: There was a window where on low-utilization systems monitor intervals were at risk for being skipped. The window is now closed.
Sleeping sibling thread: There were cases in SMT-2 where one logical CPU queued work onto its own DSVBK, and the sibling logical CPU was in wait state, and the enqueueing logical CPU did not wake up the sleeping sibling. The wakeup problem is repaired.