Need some assistance on understanding a workload comparison. Here is what we have:
We run a business workload (Java/WebSphere) for one week on an HP DL585 G5 server four Quad-Core AMD Opteron Processors, model 8389 (2.9GHz) on Red Hat Enterprise Linux 4 kernel version 2.6.9. This is virtualized under VMware ESX. Using /proc/$$/stat, we see that our process id consumed 23,525 seconds of "cpu time". We are basing this "cpu time" on the utime/stime values (from issuing a cat against /proc/$$/stat). Our understanding is that this is giving us the total jiffies consumed, and we are then dividing this by 1000 since the jiffy timer is a millisecond. That is how we calculated the "cpu time" in seconds. We ran this same load on a System z10 EC for a week. This is a z/VM 5.3 LPAR with RHEL4 running as a guest. On the mainframe, we see that our process id consumed 25,649 seconds of "cpu time". We generated what we call an equivalence factor: 23,525 / 25,649 = 0.9172 Based on this, we believe that we'll need ~10% more z10 CPU cores to process our workload than we would on our comparison platform. Question for the audience is - are we not understanding jiffies or the /proc/$$/stat timers for cpu calculation correctly? Wondering if we might be missing something insanely obvious in comparing cpu time (cores) in this fashion, or if this does seem reasonable for a Java/WebSphere workload. For reference, we have someone in doing a TCO for our workload using generalized spreadsheets for the calculations and we are using our internal comparison and the numbers are way off for the total estimated IFL count. For an example of what I'm talking about here, say we have 68 x86 cores for this workload. During overlapping peak times we are totally consuming 30 of these. Based on our equivalence factor calculation above, we are saying that we'll need >30 IFLs to handle these peaks. Based on the generalized spreadsheet calculations from those doing the TCO they claim we can run this peak workload in 8 IFLs. So essentially my main question from your experiences are if our own calculations make more sense or if the generalized spreadsheet can/cannot be trusted for accuracy. Any advice or experiences would be welcomed. Tom Stewart Mainframe OS, Networking & Security Deere & Company Computer Center www.johndeere.com ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
