VM builds a VMDBK for each cpu and can dispatch them independently of each other. This is an advantage for a guest O/S that is capable of using more than one cpu - the likes of TPF, z/OS, Linux, VSE - but not for CMS or other single cpu systems.
Regards, Richard Schuh ________________________________ From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Huegel, Thomas Sent: Friday, March 23, 2007 11:53 AM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: CPU usage -- virtual or dedicated ? 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? -----Original Message----- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] Behalf Of Stracka, James (GTI) Sent: Friday, March 23, 2007 1:18 PM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: CPU usage -- virtual or dedicated ? I am not in favor of dedicating virtual CPUs as this restricts the other users of the system and is a potential waste of resources and money. Since the CP Scheduler does an excellent job of distribution of the resources, then using the SHARE command might be better. Assuming there are more than two VSE machines of which two really need to use two virtual CPUs each and there are four real CPUs, then if I am correct issue two SET SHARE commands: set share vseguest1 relative 100 absolute 49% limithard set share vseguest2 relative 100 absolute 49% limithard Okay, it could be absolute 50% but if both VSE guests wanted the maximum resources at the same time, no other work would get done. My understanding of those two commands is that they would allow either VSE guest to get almost the full usage of two real CPUs each any time they need them. Stated another way, either could at most get 49% of the box leaving the remaining 51% for all the other users of the four CPUs. If both wanted the maximum at the same time it would be 49% for vseguest1, 49% for vseguest2 and 2% for the remaining users. Any other time, the workload would be spread evenly among all the guests in the box given QUICKDSP and other SHARE settings. Am I correct? -----Original Message----- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Stephen Frazier Sent: Friday, March 23, 2007 11:40 AM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: CPU usage -- virtual or dedicated ? Many VSE shops have been running on multiple processors for a long time. We first started it on the 4381. Adding virtual processors to VSE improves performance but not as much as most people expect. With 2 processors you get about 180% of one processor. With 3 processors you get about 240%. More than 3 processors gives very little if any improvement. I have not found that dedicating a processor to VSE does any good. Others have done it. My recommendation with several processors. Define multiple VSE guests and divide the workload among them. Give each guest 2 virtual processors. Let VM decide how to dispatch the virtual processors on the real processors. These recommendations assume any VSE after about VSE/ESA 2.4 using the turbo dispatcher and a VM after HPO. :) Posted to both VM-L and VSE-L. [EMAIL PROTECTED] wrote: > I picked this up from the VSE-L, but it is a good question for VM. I > think many VSE shops are seeing multiple processors for the first time > when they move to z-hardware and under VM it can be confussing as what > to do with 4 processors. > > The question(s) arise. > 1) Is anything gained by giving VSE more than 1 virtual CPU? > 2) With only 4 to go around does dedicating processors to VSE make > sense? > 3) Would the answers be any different depending on the number of guest VSE? > > Assume z/VM 5.2 and z/VSE 3.1 > > Thanks -- Stephen Frazier Information Technology Unit Oklahoma Department of Corrections 3400 Martin Luther King Oklahoma City, Ok, 73111-4298 Tel.: (405) 425-2549 Fax: (405) 425-2554 Pager: (405) 690-1828 email: stevef%doc.state.ok.us -------------------------------------------------------- If you are not an intended recipient of this e-mail, please notify the sender, delete it and do not read, act upon, print, disclose, copy, retain or redistribute it. Click here for important additional terms relating to this e-mail. http://www.ml.com/email_terms/ -------------------------------------------------------- __________________________________________________________________ << ella for Spam Control >> has removed VSE-List messages and set aside VM-List for me You can use it too - and it's FREE! http://www.ellaforspam.com
