Never worked on mainframes myself, but have on Unix (and Linux) a lot. Had read some years ago that mainframes had some powerful features that were often not available on Unixes. One such feature that was available, could be HP's PRM (Process Resource Manager), which, IIRC (from my time at a HP joint venture), could ensure allocation of a guaranteed minimum percentage of system resources (such as RAM and CPU time) to a specific process (say a payroll job running at the end of the month). I remember being impressed by the concept at the time.
There was also HP MC/Service Guard, but didn't have a good idea what it did, just remember the name.
P.S. Had also tried out rtprio and prioc(n)tl on some Unix boxes, maybe one was an HP one, the other a SVR4. They allowed assigning (quite) higher priorities to specified processes, IIRC.
P.P.S. Both those product names could have been changed by now, or been merged into bigger products, as sometimes happens.
Edited to say that HP's PRM _was_ an example of a mainframe-like feature.
The JIT scheme worked well for future-proofing for decades. That means it's an approach others should consider emulating if they're not yet. Only thing I couldn't figure out, due to IBM terminology, is if the compiled output is actual microcode or just CPU instructions. Or if they both create a optimized, microcode implementation and a JIT to move things to it.
Integrating DB-like functionality into the system was ahead of time. The original, System/38, had capability security in the hardware enforcing an object-based view of memory with permissible operations on different types of objects: processes, I/O, arrays, stacks, and so on. The security implications of that means I'd recommend one to a business in a heartbeat if they hadn't ditched that for POWER.
All in all, System/38 was a very, forward-thinking and practical design that continues to prove itself year after year. If it doesn't exist, I'd like to see a Lesson's Learned report on that project and how the team decided what would be in it.
OS/400 doesn't run on s390/zenterprise. It runs on pSeries (POWER8), which also run AIX and Linux.
OS/400/IBM i (or whatever its called this week) is actually probably one of the cooler OS's still around. It should be mandatory study in any comp sci/comp eng OS classes, but sadly its not and because of that, a lot of wheels are being reinvented.
Java JIT doesn't write machine code to disk. OS/400 does, and then it re-uses the machine code until it no longer exists (you move to new hardware) or the bytecode is newer (you change the program and recompile), at which point it compiles the bytecode to machine code and stores it to disk again.
You just need to look to the correct JVM. Apparently people keep forgetting Java is like C and C++. There are plenty options to choose from and OpenJDK only plays the role of reference implementation.
Actually I was thinking more about some Oberon versions that used a JIT, the way .NET is integrated into Windows, specially on the mobile since version 7.
Also the way Java gets used on Android and other embedded platforms.
Ah, Oberon. Don't know much about it. But do somewhat remember an interesting feature of it from a BYTE or other computer mag article: You could write a subroutine once and then have it available in the whole operating system - something like that. My description might not be right but I remember thinking the feature was powerful at the time.
Didn't know, thanks. Also saw that you just posted a link to an article about Mesa on HN. Viewed it briefly. It says the Alto file system was written in "BPCL". Should that BCPL, a precursor of C? Had read a book it, by Martin Richards, IIRC, long ago. Good read. I think it had only one type - machine words. Fun to implement higher level stuff on such a base, though tedious by today's HLL standards.
BCPL, an interpretive implementation of the BCPL language and system, including many demonstration programs. Click on BCPL.html to obtain a copy of the current version. This version can be installed easily on most machines running Linux, Windows and MAC OSX. In particular, it is easy to install this version on the Raspberry Pi machine. See the Young Person's Guide to BCPL Programming on the Raspberry Pi (bcpl4raspi.pdf) for details.
He was awarded the IEEE Computer Society's Computer Pioneer Award in 2003 for "pioneering system software portability through the programming language BCPL".[9]
Bitcode isn't JIT (yet); it simply allows Apple to compile binaries targeted at new devices or with newer compilers, without the developer having to do anything.
Never worked on mainframes myself, but have on Unix (and Linux) a lot. Had read some years ago that mainframes had some powerful features that were often not available on Unixes. One such feature that was available, could be HP's PRM (Process Resource Manager), which, IIRC (from my time at a HP joint venture), could ensure allocation of a guaranteed minimum percentage of system resources (such as RAM and CPU time) to a specific process (say a payroll job running at the end of the month). I remember being impressed by the concept at the time.
There was also HP MC/Service Guard, but didn't have a good idea what it did, just remember the name.
P.S. Had also tried out rtprio and prioc(n)tl on some Unix boxes, maybe one was an HP one, the other a SVR4. They allowed assigning (quite) higher priorities to specified processes, IIRC.
P.P.S. Both those product names could have been changed by now, or been merged into bigger products, as sometimes happens.
Edited to say that HP's PRM _was_ an example of a mainframe-like feature.