Good day list I would like to understand something that is not still clear to me regarding PR/SM dispatching. Just to be clear I'm asking only about shared processors (not dedicated) and with dynamically determined time slices.
I'm interested to understand the LPAR dispatching (before I understand the zVM dispatching and the Linux under VM dispatching ;-) I a-priori apologize if I'm asking too many questions together. The questions are: Question 1 ========== Does PR/SM dispatches an LPAR only when the number of physical processors awaiting allows to dispatch all the logical processors required for an LPAR simultaneously? For example suppose my machine has 3 physical CPUs, and with 3 lpars defined as follows: LPARA 3 logical processors LPARB 2 logical processors LPARC 2 logical processors Option 1 Am I wasting a physical processor when LPARB or LPARC are dispatched? Option 2 - Or can the single physical processor left be dispatched to serve another lpar? If option 2 is the true one, are there spin-lock and loop related problems if only a subset of CPUs is dispatched by PR/SM? Option 3 - Or none of the options 1 and 2 are true and it works differently? Question 2 ========== Suppose that an LPAR running z/OS with 2 physical processors is dispatched. The first physical processor completed its work. The second physical processor is still burning cycles with for example the CICS QR TCB In other words, my z/OS at some moment got 2 physical CPUs but only one TCB has really work to do. Are both physical processors returned simultaneously to PR/SM or are they returned independently to PR/SM as they become idle? I mean, do the processors return one by one to the pool of available physical processors or simultaneously on an LPAR base? Question 3 ========== Suppose that I have 2 LPARs, one with weight 20 and the other with weight 80 The one with weight 80 does not consume all its time slice and returns the processor(s) to PR/SM The one with weight 20 finds a way to use those cycles the other left Now the LPAR with weight 80 wants more than its weight Over which time interval are the weights averaged? Once a second? Once a minute? Not averaged at all? Thanks in advance for your help. Mauri. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN
