On Wed, Sep 16, 2009 at 3:06 PM, Huegel, Thomas <thue...@kable.com> wrote:
> I don't know that I want CP to do anything different than it does now > EXCEPT I want z/VM to a) keep running and b) have some facility that I > can use to be able to examine the system to find/fix the problem... I > I agree. The mainframe has a long history of managing over committed resources, but Linux is presenting new challenges since it was not written to be virtualized. Rob noted earlier: > One of the problems with booting Linux is that it determines the size > of the virtual machine by testing pages rather than ask CP about it. It seems to me that this will become a problem in other virtual environments as well and, similar to the timer tick problem, another opportunity for the mainframe to show Linux a better way to behave. If Linux does not use up all available space when it starts, there is opportunity to monitor and intervene before it gets critical. Then we do not have to worry about making sure all our virtual blocks fit in the virtual toy box. > don't know/care how that get's done, maybe reserving some page space for > CP and/or a special 'hook' into the HMC.. I'll leave that up to the > developers. > > -----Original Message----- > From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On > Behalf Of P S > Sent: Wednesday, September 16, 2009 12:53 PM > To: IBMVM@LISTSERV.UARK.EDU > Subject: Re: VM lockup due to storage typo > > On Wed, Sep 16, 2009 at 10:42 AM, Schuh, Richard <rsc...@visa.com> > wrote: > > Logon would not be the right or only place to put it. DEF STOR is > another possible place to err if the maximum storage was too high. > Perhaps a check of virtual storage at IPL time. That is a common point > that must be traversed no matter where the error occurred. > > Suggest this not get hung up on "But it won't be perfect" ideas. For > DIRMAINT, perhaps a site configuration option could say "Warn me if a > userid is defined with either storage limit above x". Similarly, at > LOGON or DEFINE STORAGE, if the VMsize is > than the total page space > defined, a warning would be useful. > > This doesn't help for aggregate overload (20x1GB with 4GB of page > space), doesn't guarantee that XAUTOLOG BIGPIG won't spiral the system > into the ground before the operator (what operator?) can react, etc., > but it would at least give some more informed consent. > > In this era of Big Numbers and big Linux guests, this is probably more > important than it used to be -- in days of yore, if you accidentally > defined a 32MB guest on an 8MB system, (a) there probably WAS enough > page space, and (b) the user was probably CMS and wouldn't touch the > pages that fast anyway. > Ethan
