Tom, So you're going to drive in peak hour you'll burn more petrol going from A to B than in off-peak hours. When I worked on chargeback the internal customers understood this concept.
Ron > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On > Behalf Of Tom Marchant > Sent: Monday, February 04, 2008 4:24 PM > To: [email protected] > Subject: Re: [IBM-MAIN] CPU time differences for the same job > > > Ahh.... Charge back. That's a difficult subject. Still, you need > not > necessarily throw much of it out. The effects that I was describing > might be > difficult to show. > > If I were to try to demonstrate these effects on a z9 BC, here's ow I'd > set up > a test. First, I'd need an LPAR with an extremely low weight. Perhaps > a > weight of 1 with the other LPARs adding up to a few hundred. My test > LPAR > would get very poor service indeed. I'd load down my other LPARs with > programs that would not do any I/O and that would reference a *lot* of > storage. The BC has 256K of data cache and 256K of instruction cache > on > each PU. In addition, there is 40 MB of Level 2 cache on the MCM. I'd > have > each of these programs reference enough memory to (probably) use every > line > in secondary cache, perhaps by dividing a 40 MB area into two 20 MB > sections > and moving data back and forth between them. I'd run several of these > on my > high weight LPARs, at least as many as there were LPs on each > partition. I'd > run a few on the low weight partition, too, but there I'd make sure > that they > had a lower priority than my test program. The test program would > reference > a byte of memory at 64 byte intervals over a range of perhaps 64K. > Then it > would issue a STIMER WAIT. A few seconds should be sufficient. During > the > time that it was waiting, its cache would tend to all be stolen and the > next > time it would have to go to main store again. It might take a few > thousand > iterations to use enough CPU to be measurable. Repeat the test on a > lightly > loaded LPAR with little memory contention from other LPARs and I'm sure > it > would use considerably less CPU time. > > -- > Tom Marchant > ---------------------------------------------------------------------- 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
