================================================ -----Original Message----- From: "McKown, John" <[EMAIL PROTECTED]> Sent: 7/19/2006 12:23 PM To: "IBM-MAIN@BAMA.UA.EDU" <IBM-MAIN@BAMA.UA.EDU> Subject: Re: Why is zSeries so CPU poor?
<snip> > > I doubt that IBM could remove generally documented machine > instructions or system services. The JVM is allowed to call > JNI (Java Native Interface) routines, written in any language > (usually C), which are allowed by definition to use any > operating system services and any machine dependent features. > > > Jeffrey D. Smith If so, then I wonder what causes a "machine check" when you try to IPL z/OS on an IFL. Yes, I did it out of curiousity. And I know that an IFL is not a zAAP. But it is another "speciality engine" (I think that's the term IBM uses). I have read that some things cannot be handled by a zAAP such as timer and I/O interrupts. There must be something "special" about them to disallow this (or maybe the control regs for the processor are set to disable them, I guess is a possibility). Then the question becomes: Does the JVM tell the z/OS dispatcher move the work from the zAAP to a general CPU while doing a JNI call? Or does it leave it on the zAAP? I don't know. If it leaves it on the zAAP, then I'd really push to "wrap" a lot of COBOL code as a JNI from Java. I could then run the majority of my applications on a zAAP and get some nice performance! -- John McKown ================================================ I can only venture a guess that it is similar to a nullifying program interrupt occurring for a "disabled" machine instruction. The operating system sees the special program interrupt and schedules the unit of work for redispatch on a CPU that has it installed. The original crypto (and I think vector) instructions had a special nullifying program interrupt X'01xx' that caused redispatch on the correct CPU. I haven't a clue when the operating system decides that it's ok to move the work back to the original CPU. Jeffrey D. Smith Farsight Systems Corporation 24 BURLINGTON DR LONGMONT, CO 80501 303-774-9381 direct 303-709-8153 cell 303-484-6170 fax ---------------------------------------------------------------------- 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
