Service news: HiperSockets performance in z/VM guests
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There is a z/VM APAR available, that resolves performance issues when using HiperSockets connections for Linux environments.
z/VSE APAR VM65992: HIPERSOCKETS PERFORMANCE ISSUES ON SHORT BUSY
Error description: Using a dedicated HiperSockets device in a virtual machine running Linux exploiting QDIO Enhanced Buffer State Management (QEBSM), may experience slow performance in a very highly contested LPAR to LPAR communication environment. This is an environment where multiple HiperSockets data transmissions occur simultaneously to the same set of QDIO queues. It's this contested environment which increases the likelihood of a HiperSockets device presenting a short busy condition on a Signal Adapter (SIGA) Instruction issued by a program (the Linux Guest in this case). It is the occurrence of a HiperSockets short busy which opens an error window that may cause the problem to occur. Running with QIOASSIST OFF increases the likelihood of seeing this problem.