Great questions. I have no idea of the answers, but will be very interested to see them!
On Sun, Dec 18, 2011 at 10:50 AM, Mauri Kanter <[email protected]> wrote: > 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 [email protected] with the message: INFO IBM-MAIN -- zMan -- "I've got a mainframe and I'm not afraid to use it" ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
