Avoid privileged instructions, such as IO and paging. Here VM's Minidisk cache can help to avoid I/O. You'd cache at the highest level, that is use VSE caching as much as possible, then VM/ESA's; you'd turn off MDC in z/VM, it is of no use to have two MDC levels.
Have you looked at a performance monitor? Is the CPU full indeed?. Multiple processor configs would cause higher overheads too I guess and VSE's turbodispatcher is(was?) known not to be very performant, but if the VSE load requires more than one CP, you have no choice. I guess you know it is useless to define more virtual CP's than you have real ones available. 2009/4/29 Berry van Sleeuwen <berry.vansleeu...@xs4all.nl> > > Hello listers, > > Before I begin, yes I know third level will cost us. Since SIE doesn't get > down to the VSE we do not benefit from that and all CPU has to be emulated. > > We have moved an old VM/ESA 2.2 with VSE 2.3 to a new z890 machine. > Obviously this level of VM can't run on zseries so we have put the VM into > an zVM 5.4 LPAR. It does run and since they came from an old (ESCON) machine > the batch (mostly IO) runs very good. > > We did expect to see some performance penalties and we already sized the > machine to twice the MIPS they used to have. And for the most part the guest > VM has a TV ratio between 1.9 and 2.5. Usually during batch the TV is just > above 2 but during online hours we also see a TV above 3. There are a few > transactions that have a very bad performance. (from 2 seconds to 2.5 > minutes) The time also depends on the other load in the VSE (or perhaps even > in the CICS). > > We have been playing with lots of settings. Such as, two virtual CPU's in > the guest, two virtual CPU's in VSE with TurboDispatcher, one dedicated CPU > to the guest VM. > > Any ideas on how to speed up the guests? Other than migrating the guest VM > to the zVM 5.4 host? > > TIA, Berry. -- Kris Buelens, IBM Belgium, VM customer support
