On Friday, 03/23/2007 at 01:52 EST, "Huegel, Thomas" <[EMAIL PROTECTED]> wrote: > I don't use the share settings as you suggested I have 7 full production VSE's > and use VM Resource Manager to dynamically change the share settings as the > workloads change. This seems to work very well. But I don't seem to totally > understand is what advantages (or disadvantages) there are to giving the VSE's > multiple virtual CPU's. I seem to remember some discussion that z/LINUX will > eat up as many cpu's as it can get.. and one must be carefull. > > Does VM really dispatch the guest on more than one processor? Just how does it > work?
Each virtual CPU is running some work. CP has some number of logical processors to choose from. When a logcial CPU becomes available, pick the next virtual CPU and plops it down on a real one. (An extremely simplified version of what really happens.) And away we go... The implication is that multiple virtual CPUs in a guest are interesting only if the guest is capable of using multiple CPUs. VSE is certainly capable of that. Whether you get *benefit* is another story and is based on what VSE performance reports show you. If you have work that is waiting on a CPU, an extra virtual CPU may help. I get the impression that a lot of old, expired "wisdom" about VSE is running around Out There based on the days when it only ran on one CPU. But it is a Bad Idea to every allocate more virtual CPUs to a guest that you have logical CPUs defined to the VM LPAR. Alan Altmark z/VM Development IBM Endicott
