There is probably a start-up overhead that is fixed, regardless of the transaction rate. So, the more transactions running the lower this per transaction cost appears.
Example: Assumptions: Fixed overhead: 10 seconds Cost/transaction: 1 second For one transaction: 10+1 = 11 seconds/tx For two: 10+2 = 12 divide by two: 6/tx The above are for illustration only. - -teD 300,000 Kilometres per Second Not only is it a good idea! It's the LAW!!! -----Original Message----- From: Charles Mills <[email protected]> Sender: IBM Mainframe Discussion List <[email protected]> Date: Fri, 31 Jan 2014 09:52:53 To: <[email protected]> Reply-To: IBM Mainframe Discussion List <[email protected]> Subject: Re: CPU time I am responsible for a z/OS program that runs as a started task and processes asynchronous "events." (IEFU8x exits being driven with particular SMF records, but no matter.) After much head-scratching, I figured out that CPU time per event was GREATLY and fairly predictably affected by how rapidly the events occurred! I have a "driver" program that I can use to artificially push simulated SMF records through the program, and I found that if I run that driver program at a leisurely pace, perhaps 15 events per second, then 1000 records consume about .2 CPU seconds. But if I drive records through the program as fast as it can handle them -- about 12,000 records per second -- then each 1000 records consume about .083 CPU seconds -- LESS THAN HALF as much. (If you do the arithmetic you can see that at 12,000 records per second the program is pegging one CPU at 100%.) BTW, the program is single-thread and cannot exploit multiple CPUs. I don't really know, but my conclusion is that either "getting interrupted" consumes a fair amount of CPU time, or else that if the program is busy continuously it tends to "own" the instruction and data caches, which saves a lot of CPU time. I would be interested in any comments on the situation or my analysis of it. I'm not "unhappy" or terribly surprised -- this is just engineering intelligence I am after here. It's kind of a good thing: the busier the program is, the better it runs. A much more favorable situation than the other way around. Charles -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Ed Jaffe Sent: Thursday, January 30, 2014 10:30 PM To: [email protected] Subject: Re: CPU time On 1/30/2014 9:30 PM, Ron Thomas wrote: > Hello. I have a program that i am executing 2 times the number of records > that is processed is same in both the time, but i am seeing CPU execution > times are different. Can someone throw some light on why this is comming as > different? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
