Why is zSeries so CPU poor? (was:RE: Linux - Our Saving Grace?)
Just out of curiousity, why is the zSeries CPU so poor at CPU-intensive workloads, like Java? Is it the clock speed of the circuitry? Is it the complexity of the instructions? Is it the fact that the machine does a lot of internal checking / checkpointing for reliability and recovery? -- John McKown Senior Systems Programmer HealthMarkets Keeping the Promise of Affordable Coverage Administrative Services Group Information Technology This message (including any attachments) contains confidential information intended for a specific individual and purpose, and its content is protected by law. If you are not the intended recipient, you should delete this message and are hereby notified that any disclosure, copying, or distribution of this transmission, or taking any action based on it, is strictly prohibited. -- 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: Why is zSeries so CPU poor? (was:RE: Linux - Our Saving Grace?)
Does IBM make a co-processor add-in that can provide an assist for the JVM overhead? -Original Message- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] Behalf Of McKown, John Sent: Wednesday, July 19, 2006 1:10 PM To: IBM-MAIN@BAMA.UA.EDU Subject: Why is zSeries so CPU poor? (was:RE: Linux - Our Saving Grace?) Just out of curiousity, why is the zSeries CPU so poor at CPU-intensive workloads, like Java? Is it the clock speed of the circuitry? Is it the complexity of the instructions? Is it the fact that the machine does a lot of internal checking / checkpointing for reliability and recovery? -- John McKown Senior Systems Programmer HealthMarkets Keeping the Promise of Affordable Coverage Administrative Services Group Information Technology This message (including any attachments) contains confidential information intended for a specific individual and purpose, and its content is protected by law. If you are not the intended recipient, you should delete this message and are hereby notified that any disclosure, copying, or distribution of this transmission, or taking any action based on it, is strictly prohibited. -- 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 -- 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: Why is zSeries so CPU poor? (was:RE: Linux - Our Saving Grace?)
In [EMAIL PROTECTED], on 07/19/2006 at 01:29 PM, Kuredjian, Michael [EMAIL PROTECTED] said: Does IBM make a co-processor add-in that can provide an assist for the JVM overhead? No, but they provide an option to dedicate a processor to Java work at a lower cost than processors allowed to run conventional workloads. -- Shmuel (Seymour J.) Metz, SysProg and JOAT ISO position; see http://patriot.net/~shmuel/resume/brief.html We don't care. We don't have to care, we're Congress. (S877: The Shut up and Eat Your spam act of 2003) -- 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: Why is zSeries so CPU poor? (was:RE: Linux - Our Saving Grace?)
In [EMAIL PROTECTED], on 07/19/2006 at 12:10 PM, McKown, John [EMAIL PROTECTED] said: Just out of curiousity, why is the zSeries CPU so poor at CPU-intensive workloads, like Java? Is it the clock speed of the circuitry? Is it the complexity of the instructions? Is it the fact that the machine does a lot of internal checking / checkpointing for reliability and recovery? It's the fact that the processors are manufactured in low volumes. -- Shmuel (Seymour J.) Metz, SysProg and JOAT ISO position; see http://patriot.net/~shmuel/resume/brief.html We don't care. We don't have to care, we're Congress. (S877: The Shut up and Eat Your spam act of 2003) -- 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: Why is zSeries so CPU poor? (was:RE: Linux - Our Saving Grace?)
Just out of curiousity, why is the zSeries CPU so poor at CPU-intensive workloads, like Java? Is it the clock speed of the circuitry? Is it the complexity of the instructions? Is it the fact that the machine does a lot of internal checking / checkpointing for reliability and recovery? Well first of all, I would NOT say that performance is poor. Its just not as good on certain types of workload and also tends to run at a lower clock rate than some other machines. There are quite a few reasons, rather than just one single one. The biggie IMO is that z architecture is demonically complex to implement in silicon. For a given clock rate and instruction architecture, the performance of a cpu is fairly predictable - at least analytically. So the faster you can clock it the faster it will execute instructions - all else being equal. Also, for a given fab technology there is a theoretical upper limit on the clock rate. Design complexity lowers the rate that can be achieved. Z architecture ends up needing lots of gates and logic levels and ultimately limits the clock frequency. The memory model is also more complex, but then again people tend to expect reliability rather than speed when they are messing with bank balances. There's not a lot of point clocking the cpu faster than it can eat data, so to a large extent the cpu is gated by the cache and memory subsystem design. There are also significant performance differences and design trade-offs based on the different workload mixes expected by the customer base. Z architecture favors on-chip cache area over raw clock speed. The basis of that idea is that when you run a general purpose mixed workload, you will do a lot of context switching and less raw computing. The POWER RISC guys make a different trade off to get more raw performance. So if you want to run a bomb simulation, you're better off running it on a pSeries. If you want lots of address spaces running lots of independent transactions the z may well be the better performer, even on a per-engine basis! Millicode is (among other things) an effort to improve the speed/area trade-off by removing logic from the silicon and replacing it with what is effectively software. That moves the z design closer to the POWER concept and I am guessing that trend will continue and the clock rates will get closer to their technology limits. BTW the POWER RISC designers and the z designers are the same people. They flip-flop between hardware platforms for each generation of processor technology. Technology leadership swaps back and forth between z and p. The z9 is the more recent, and probably the technology leader (for now) In raw compute power the pSeries will still win, but the z has a more balanced overall design for mixed workload throughput. CC -- 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
