Re: SMF Under VM
IBM Mainframe Discussion List wrote on 12/03/2007 01:38:46 PM: > >[EMAIL PROTECTED] (Kopischke, David G.) writes: > >From what I understand, we just use canned processes to extract > > SMF, load databases and create reports. But since we don't use VM > > at home and have no experience with it, maybe we're just not > > understanding where this data is in that environment ??? Is there > > any documentation that specifies what SMF data is available under > > VM and what is not ??? With respect to %CPU BUSY, I understand it's > > virtual under VM, but there still has to be some method of gauging > > how much CPU a guest is using, isn't there ??? How do VM shops > > report this ??? > > From the deep dark recesses of my memory > > IIRC, the MVS CPU busy is not measured directly determined by sampling > the PSW wait bit and subtracting from 100%. In a z/VM environment, the > (guest image) PSW wait bit is maintained by z/VM, either always on or > always off from the standpoint of the VM guest image. Thus any sampling > of this bit will yield either 100% busy or 0% busy. > > z/VM (of course), knows the correct answer and can report on this via > the z/VM equivalent of RMF. I forget what this is called. > > I also seem to recall that there was a method for z/VM to properly > maintain this bit but it was not the default. i.e. the z/VM sysprog > needed to modify the guest machine definition to make this happen. This > still involves the capture ratio issues discussed by Lynn Wheeler. > > Maybe someone with more recent VM experience can chip in and help me out > here? MVS uses the CPU timer to measure the time each logical CPU spends in no-work wait. Busy time is then wall clock time (TOD clock) minus wait time. A logical CPU's cpu timer continues to decrement while the logical CPU is in wait. It does not decrement while the logical CPU is not in wait and is not dispatched on a physical CPU. CPU time used as reported in SMF records is measured via the CPU timer. Thus it measures actual CPU time, and does not include time that a task spends dispatched on a logical CPU that is not dispatched on a physical CPU. Jim Mulder z/OS System Test IBM Corp. Poughkeepsie, NY -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: SMF Under VM
>[EMAIL PROTECTED] (Kopischke, David G.) writes: >From what I understand, we just use canned processes to extract > SMF, load databases and create reports. But since we don't use VM > at home and have no experience with it, maybe we're just not > understanding where this data is in that environment ??? Is there > any documentation that specifies what SMF data is available under > VM and what is not ??? With respect to %CPU BUSY, I understand it's > virtual under VM, but there still has to be some method of gauging > how much CPU a guest is using, isn't there ??? How do VM shops > report this ??? >From the deep dark recesses of my memory IIRC, the MVS CPU busy is not measured directly determined by sampling the PSW wait bit and subtracting from 100%. In a z/VM environment, the (guest image) PSW wait bit is maintained by z/VM, either always on or always off from the standpoint of the VM guest image. Thus any sampling of this bit will yield either 100% busy or 0% busy. z/VM (of course), knows the correct answer and can report on this via the z/VM equivalent of RMF. I forget what this is called. I also seem to recall that there was a method for z/VM to properly maintain this bit but it was not the default. i.e. the z/VM sysprog needed to modify the guest machine definition to make this happen. This still involves the capture ratio issues discussed by Lynn Wheeler. Maybe someone with more recent VM experience can chip in and help me out here? HTH, -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: SMF Under VM
The following message is a courtesy copy of an article
that has been posted to bit.listserv.ibm-main,alt.folklore.computers as well.
[EMAIL PROTECTED] (Kopischke, David G.) writes:
>From what I understand, we just use canned processes to extract
> SMF, load databases and create reports. But since we don't use VM
> at home and have no experience with it, maybe we're just not
> understanding where this data is in that environment ??? Is there
> any documentation that specifies what SMF data is available under
> VM and what is not ??? With respect to %CPU BUSY, I understand it's
> virtual under VM, but there still has to be some method of gauging
> how much CPU a guest is using, isn't there ??? How do VM shops
> report this ???
for decades VM would account for processor useage (both virtual and
total) which would turned out to correspond very closely with
total/actual busy (which was also measured).
other infrastructures have tended to have accounted for processor busy
which has been less than total/actual cpu busy (measured by other
methods). The "difference" (which has peridically been quite
substantial) was frequently referred to as "capture ratio" ... aka the
sometimes small percentage of cpu busy that was actually accounted for
for some, the concept of "capture ratio" took quite a bit of time to
sink thru ... since a system not accounting for all cpu useage was quite
foreign concept.
running under VM ... one possible way for handling the ("captured"
... at least by vm) non-virtual processing time might be handled along
with all the other "uncaptured" processor time (from the standpoint of a
guest operating system running in a virtual machine).
some of this also has to be handled with LPARs w/o VM software ... since
LPARs are essentially a stripped down VM subset moved into the microcode
of the machine (and then you can have virtual guests running in a VM
software virtual machine ... which, in turn might be running in a LPAR
"virtual machine" ... which is finally running on the real hardware).
a few results for quicky search engine use for term "cature ratio"
http://www-03.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/FLASH10526
http://publib.boulder.ibm.com/tividd/td/TDS390/SH19-6818-08/en_US/HTML/DRLM9mst48.htm
http://www.ibm.com/developerworks/wikis/display/zosperfinstr/Controlling+SMF+Record+Production
http://www.ibm.com/developerworks/websphere/library/techarticles/0407_garza/0407_garza.html
http://www.cmg.org/measureit/issues/mit38/m_38_10.html
the original cp67 system delivered to the univ. the last week of jan68
did have something slightly reminiscence of "uncaptured" ... which was
actual "captured" (i.e. specifically measured processor time) that
wasn't associated with any specific operation (called "overhead"). This
would increase significantly as the number of concurrent processes
increased (aka it scaled extremely poorly). I completely reworked that
implementation to eliminate the non-scaling characteristic ... as well
as being able to "account" for what was actually being done.
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SMF Under VM
Greetings, We are getting ready for our semi-annual DR test this week-end. One of the things that came out of our last test was we found we couldn't generate our usual utilization reports from the SMF data that was returned. I'm not the capacity planning person and I don't know much about what he does with the data, but the %CPU BUSY fields seem to be blank. I think there were a couple other fields acting like that as well. We run in LPAR mode at home and as a guest under VM at our DR site. The SMF data is further massaged and loaded to some sort of database by MXG processes. From what I understand, we just use canned processes to extract SMF, load databases and create reports. But since we don't use VM at home and have no experience with it, maybe we're just not understanding where this data is in that environment ??? Is there any documentation that specifies what SMF data is available under VM and what is not ??? With respect to %CPU BUSY, I understand it's virtual under VM, but there still has to be some method of gauging how much CPU a guest is using, isn't there ??? How do VM shops report this ??? Thanks again, Dave K. -- This e-mail transmission may contain information that is proprietary, privileged and/or confidential and is intended exclusively for the person(s) to whom it is addressed. Any use, copying, retention or disclosure by any person other than the intended recipient or the intended recipient's designees is strictly prohibited. If you are not the intended recipient or their designee, please notify the sender immediately by return e-mail and delete all copies. OppenheimerFunds may, at its sole discretion, monitor, review, retain and/or disclose the content of all email communications. == -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
