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Linux Possibly Ported to IBM Mainframes
Jah-Wren Ryel writes "
Vnunet is reporting
that IBM has a version of Linux ported to their S/390 mainframe
architecture waiting in the wings. Apparently there are two versions, one that runs under VM (a kind of meta-os, sort of like VMware) and one that runs on the bare hardware." An "anonymous source" and "speculation from analysts" story. Nothing official from IBM. Please read and judge accordingly.
Still, 5 years ago they were talking about how great it would be to have one OS across the board so that you wouldn't have to retrain employees as you scaled systems up from PC's. At the time, they were talking about doing that with OS/2 and we all know where that went, but Linux is out of their control so will continue to gain popularity no matter what they do with it.
It'd be cool to be able to telnet to bldvmb and get a Linux session when I log in, I hope they do this :-)
I'm trying to teach myself to set people on fire with my mind... Is it hot in here?
...take it from someone who's discussed it with the guy who actually started it. Linux/390 isn't very special, really. When I last spoke with him (I'm sorry, I've forgotten his name.. I forget names easily. :P) it just ran on the bare hardware, and didn't support much at all. If anything.
Now, some info on the S/390 from someone who's not gotten to play with one, really, but has seen one.
The S/390 is a 'massively parallel' computer. Meaning that everything is parallel. The S/390 is capable of running just about any OS you throw at it, from Linux on an x86 host controller to Windows NT on that same host controller. You can run AIX on an RS/6000 host controller. Or OS/400 on the AS/400 host controller. It's designed to do massive processing while serving up literally thousands of hosts. Usually 'dumb' terminals over twinax (twin-prong coaxial), triax (three-prong coaxial), or RS232/RS242.
No, it's not meant to run Linux instead of OS/390. I wouldn't dare to say that it should, because in truth, it shouldn't. The S/390 is not a 'convenience' machine or a 'play' machine. It is a mainframe, and it needs a mainframe OS.
However, I see absolutely no reason why Linux shouldn't run on the S/390. Bear in mind; running on the S/390 does not mean replacing OS/390. It means SUPPLEMENTING OS/390. Say you have an S/390 handling most of your financial transactions, but accounting wants a website to keep track of it. Running Linux on an x86 host controller on an S/390 is the perfect solution. But say accounting wants to cut some major expenditures out of the budget; eliminating OS/390 isn't a good idea. Plain and simple.
OS/390 is a *VERY* mature OS, pretty much dating back to OS/360 (the similarities between OS/390 and OS/370 are very obvious) and as a direct result, is rock solid stable, extremely secure, and inherently reliable. Add that in to hardware that is designed to have decades of uptime. Add in the power to get the job done and then some. That's what the S/390 is about. It's a big-bucks big-iron machine meant to be your network-edge solution for ERP and transactions and whatever else you want to throw at it. It's not your webserver, it's not your fileserver. It's a mainframe.
However, I've noticed quite a few people are moving away from S/390 to the actually more powerful RS/6000's, which lack some of the features of the S/390. Okay, MOST of the features people look for in the S/390. Some RS/6000 models border on the commodity machine definition. Linux doesn't belong there, either. Yes, that's right, you're hearing it from someone who spends about 99% of his spare time working on porting Linux more thoroughly to the RS/6000. Linux doesn't replace AIX. Period. AIX is a mature OS, probably 7 or 8 years Linux's elder. AIX has a very stable and regular release and development cycle, and is built on principles that have been proven a million times over. It's inherently reliable, stable, and very fast. Unlike Linux, AIX does not just have 'general' releases for all RS/6000's with all architecture support. There is AIX for the RS/6000 F40 (Dual PowerPC 604e) and there is AIX for the RS/6000 Power260 (single POWER3). You can't mix and match those two or components from them. AIX is optimized at the hardware level extensively. Unlike my work, it's built on native platform, optimized on that platform, and meant for that platform.
Yes, every piece of AIX has a common code base. The compilers do the work. That's why it's built on the native platform. You can get AIX C/C++ compilers for PowerPC 604e, POWER2, POWER3, and so on. And they're designed to optimize and compile reliably. ANd they do it well. Better than gcc or egcs could ever hope to.
Linux/390 is a great project. Like I said; there's no reason whatsoever that Linux should NOT be able to run on the S/390. There's no reason Linux should not be able to run on ANY system. The question is, though, do you want to replace what that system is MEANT to run with Linux?
Not yet. Linux is still a long way off from being ready to do that. But maybe someday it will be ready.
-RISCy Business
your company here.
shelby != ford
It is conceivable to purchase a mainframe class machine for hobbyist use. Grant it, it would be a pretty expensive hobby. Used machines are very plentiful on the market, but hardly practical for use in your basement or den. IBM has the P/390, which is a Mainframe class processor in a server. They probably start at around $10000-$20000, not including M/F software. There is a company that sell emulation software that will turn your Intel box into a mainframe. These products get very respectable performance, even compared to todays mainframe class machines. This obviously depends upon how many Mhz you throw at it. The product is called Flex/ES.
Having worked for Lockheed-Martin for a while, and run their mainframe shop, we had 3 MVS machines and 2 VM machines. During the 2 years, we had exactly 1 unscheduled IPL, which was related to a power failure of the motor-generator for one VM machine. Other than that, and the required IPL for DST, the only reboots were related to OS updates (at most once a year). Average "uptime" was 6 months.
You are right. The mainframe MCMs are not ppc chips at all, in any way. That was a silly comment. At this point, the only difference between the AS400s and the RS6000s is the microcode.
Well, I worked in a Fortune 500 data center and in ten years, we had the box down a total of five times, and one of those times was for a move from the old data center to the new one and another was after a serious "water incident" on the floor above. I think that your shop was not run as well as it should have been.
Hmm. IBM scared to death of java at the high end? Don't think so. If you look inside a big data center (big, like billions of dollars worth of hardware), you see practically every kind of hardware in there. And you see IBM at the core. Being part of the core ops, you have to talk to everyone, no matter what OS it is. This means java.
IBM isn't pushing java, its customers are. The big guys want it more than anyone, because when you come right down to it, java reduces their cost to develop software. This cost is enormous, and is exacerbated by the multiple platforms they run.
And IBM being IBM, when money talks, they listen...hard.
I hope this new effort doesn't have any of these limitations. I remember how creepy it was to have a Unix command called "vmpunch", which submitted JCL files to the VM system. Ug.
[ReidNews]
Just a comment on the side. Do you know that Siemens uses in their BS2000 systems S/390 processors? I believe there are mostly political reasons why OS/390 doesn't run on BS2000 and vice versa. I'm sure Linux/390(if it ever exists)could also run on BS2000.
That is not true. IBM just does not talk about their rumored Linux port to S/390 very much at all. I believe that if it is true, there may be developers within IBM that would like to talk about it and to share it with the out in the open development, but do not dare because if the do they could easily loose their job. As i know IBM and especially the S/390 division, my guess would be that it takes 6 month to port Linux and 12 month to get it through the legal departments....
True.
Then go and download a precompiled kernel and bootloader from http://www.linas.org/linux/i370.html. Note that this is a port that Linas Vepstas and others have been working on for some time now -- it's different to the rumoured "official" Linux port by IBM to which this story refers.
"The invisible and the non-existent look very much alike." -- Delos B. McKown
The purpose won't fall within the realm of most users, but it would be to run Linux along with other legacy apps on the same machine. Lest anyone think this is an entirely stupid idea, the place I used to work had an S/390 mainframe running legacy apps that are unlikely to be changed anytime soon, and we wanted to make use of some of the OMVS features on the machine. OMVS is supposed to be a UNIX-compatible OS running on the S/390. The machine was perfectly capable, if incredibly overpowered and overpriced for the simple purpose of getting at the unused disk storage we had for it via UNIX-type software. But OMVS was a real pain. The reason? It just wasn't convenient to compile for. We could download software all day, but if we wanted to run something of our own design or just compile the latest version of some kind of freeware for it we were out of luck without an army of IBM technicians to help us out. I personally wasn't a real supporter of keeping the mainframe around, but Linux as a VM partition would have at least been infinitely preferable to the proprietary system they were using, in openness and plain convenience. There are lots of possibilities for a system like this running on the existing mainframes out there. It allows integration of UNIX software into a mainframe shop's army of old-school applications, and increased use of underutilized hardware.
more proof that the powers that be are waking up. only linux is ready for enterprise computing and only linux can take advantage of powerful mainframe computers.
fact, linux will be the only os in 2 years. isnt progress wonderful?
linux, the choice of a GNU generation
Not only that, but you could run multiple copies of the SAME OS, just like one of those Russian nesting doll sets. So you could debug mods to your own OS in a virtual environment before deploying them to the real machine.
More than six years ago -- more like 12. I remember playing with it before there *were* RS/6000s -- AIX ran on some other early IBM workstation hardware at that time.
It would have given Sun an advantage; and they
are a major competitor to IBM's mainframe dept
I'm sure.
Linux would be a different Unix - it would level
the field a bit more.
It is a better choice than either NT or Java, but
I am curious why it hasn't been done with AIX yet.
Reminds me of a joke press release from Borland Int'l a while back: "Announcing Turbo Cobol for your mainframe! BI really stands for Big Iron..."
... think device drivers ... "XFree3270 has just announced support for the latest IBM BluHat(r) Linux kernel build (3.0.3) for S/390 processors."
Come to think of it, though this may be real, it could still be a trial balloon... Though IBM occasionally develops insanely alright technologies, it's known also for internecine warfare that kills said tech in the cradle... mainframe group killing multitasking o/s initiative (rumor from the middle 80's).
As legend has it, IBM's makes most profit from sales of hardware... so, so what if Linux is given free with a gigabuck machine, when the markup on the iron is prolly 200%!!?
And if you consider the version running under VM (VM/Linux? Linux/VM? ye gods..) it's just another application on a large timeshare appliance.
I don't see a conflict. This'll probably stimulate mainframe sales and free software dev. The word "Linux" has strong buzz and cachet, and even if the CIO doesn't "get" oss/gnu/etc, he's further increased his career trajectory by getting into the "latest" tech in a safe (and very expensive -think IBM tech support acolytes) way -but, hey, that's okay. Win-win.
Get ready
Ugh. Even if it does become a reality, the "synergy's" gonna be upward, not so much downward, doncha think? I mean, what does IBM mainframe world, albeit running Linux, have to offer the single-user Linux world? Gotta think about that...
-schmaltz
Big Daddy, Johnny, Burp, Aunt Zelda, Scott, Slurp, Big Momma
Not sure why you said IBM ran away from java on the mainframes. They have Websphere ported to all platforms from linux to AIX to the S/390. They are completely embracing java on the S/390; just released jdk 1.1.8, have JDBC driver right into DB/2, ECS calls right into CICS, java RACF interface classes. Where have you been?
IBM already has created "Unix System Services" on 390's running OS390. You have to have it installed and configured in order to use TCP/IP on new versions of OS390. If they replaced it with Linux it would make it a whole lot easier and enjoyable. "Unix System Services" is a pretty lame shell if you ask me. -I drink, therefore I am.
I drink, therefore I am.
Well I work for Bank Of America on the mainframe side of the shop and IBM already has Unix(AIX) running on S/390. It is called Unix System Services. You are right about it running in a virtual environment. As a matter of fact they(IBM) have already got Apache running in this environment. Their goal is to eventually get the Lotus Domino servers running in this environment also. We are in the process of setting up a all java based reporting system that will have live real time acess and update capability to DB2. The reasoning behind the use of a machine like the mainframe is the fact we will have up to 100,000 people acessing dynamically created reports all delivered through the corporate intranet to the banking centers. Especially with the new JDBC drivers that DB2 is now supporting it really runs smoothly. I even talked to some of the IBM reps who said to most software it looks just like they are running on AIX and then the Unix System Services make the apropriate calls to S/390. I guess my real question would be why would IBM want to port Linux for the mainframe when they already have AIX running smoothly there?? Can anyone tell me what you gain from running Linux instead of Unix???? Just my two cents on the subject.
--- Errr......No I don't need more oral sex thank you, Windows goes down on me all the time.
This is not true any more. There is a JDK1.1.8p and 1.2 is in development and they promised that it should come out 2-3 month after the IBM JDK for NT. They have the WebSphere AppServer 1.2(Enterprise Edition) and i know it can do Servlets, JSP, but not EJBs at the moment. And if you get your hands on the VisualAge for Java Enterprise Edition, it has support for almost everything. MQ, DB2(JDBC), CICS, IMS, RAWT, VSAM I/O, even a class library to access RACF. There are even thoughts about supporting SanFransisco on S/390. And CICS has special Java support. For the new CICS 1.3 you can write the transactions in java. If you look at www.ibm.com/vadd, there is a nice example how to call a java CICS transaction from a applet via IIOP. And there is some talk for the next CICS to have a buildin EJB runtime.
When did you try it? It is true that IBM was late with Java on S/390 and they had there problems to get it running. But i know of own experience that it works fine now. I just created a JavaBean with Websphere Studio on NT and deployed it without code changes on OS/390 in the WAS 1.2. I also believe that they see the value of Java on S/390 in web enabling and integration of legacy applications. To CICS or DB2 on Linux/390. I don't think it makes sense on its own. If i just do a DRDA from DB2 on Linux/390 to DB2 on OS/390, i could also use a RS6000 instead of the Linux. It would be something completely different, if the DB2 on Linux could work together with the DB2 on OS/390 in a parallel sysplex and access the coupling facility. Then you could have DB2 on Linux as an good interface to the old database on OS/390. Or imagine something like GRS over a coupling facility for several Linux/390. They could even share DASD like with S/390! That would give Linux/390 some value!
Wow, a mainframe that runs TCP/IP. The manufacturers of 3270 controllers will be unhappy.
-Chris
Not to mention the specialized hardware IBM mainframes use. It's not just a CPU and a few busses you have to be worried about. Literally *everything* has its own controller. Code would need to be written for so many things besides simply the CPU that, when all is said and done, what you'd have would be a far cry from the Linux we all know and love.
To put it bluntly: I'll believe it when I see it.
- A.P.
--
"One World, one Web, one Program" - Microsoft promotional ad
"Remember when the U.S. had a drug problem, and then we declared a War On Drugs, and now you can't buy drugs anymore?"
i think this would be a excellent step for IBM, i do a lot of work regarding SAP, ORACLE, BAAN, etc. and IBM is probably the least represented hardware Ive seen, this should open the doors of the market for them by providing a somewhat standard API for developers to work against, instead of their proprietary architecture.
May the forces of evil be confused on the way to your inbox.
Pssst...I'll tell you why they did it. it wasn't a company decision. A couple of geeks in Germany were bored and did it on their own time, to prove they could do it, just like much of linux is done: to prove you can do it, and do it better than anyone else. I don't know how well it works; i haven't seen it yet.
Of course, I'm an anonymous coward, so you can choose to believe it or not. This is what my boss's boss's boss's boss said. Seeing as he's management, though, think what you wish.
some.random.guy@us.ibm.com
maybe get a beowulf of these going ;)
Pssst...I'll tell you why they did it. it wasn't a company decision. A couple of geeks in Germany were bored and did it on their own time, to prove they could do it, just like much of linux is done: to prove you can do it, and do it better than anyone else. Then the company said 'wow! that would be cool! let's work on that.' I don't know how well it works; i haven't seen it yet.Of course, I'm an anonymous coward, so you can choose to believe it or not. This is what my boss's boss's boss's boss said at an informal gathering (he's head of server division). Seeing as he's management, though, think what you wish. some.random.guy@us.ibm.com
Your comment about IBM shying away from Java on their mainframes is just not true. When I worked at Hursley they were spending a lot of time and effort on Java, particularly on CICS. Java is seen
as a good replacement for COBOL in the CICS environment. With multi-heap JVM's and some innovative garbage collection techniques they were
expecting Java performance to be on a par with COBOL within 12 months.
Daniel.
The NetBSD project already has a port to the VAX desktops and some mainframes. See NetBSD/Vax It's not stable though...
It's interesting that IBM would do their own port of Linux.. I wonder what's wrong with their current mainframe OS?
Why is this post moderated to 1? This post points to EXACTLY what the article is talking about! Get over yourselves, you stupid moderators.
"if there is tuned software available for a platform, this is typically a better choise than 'agnostic' software such as linux".,
is valid, but I would counter that in many cases, the increased performance of hardware is making the cost of maintaining tuned software prohibitive.
Look at web serving, for example. Perhaps its simply the timliness of the web that is forcing IBM to market AIX boxes as webservers, but nonetheless its out there in print. In such a case I would argue that simply having two FreeBSD boxes instead of one AIX box is going to give you the equivalent aggregate performance.
Stock hardware and software are slowly closing in on the tuned, expensive alternative. AIX and Solaris are in genuine danger of being made obselete by Linux and FreeBSD, if hardware continues to get cheaper and faster simultaneously. As the number of applications for which Solaris or AIX is preferred continues to shrink, the cost of maintaining them will outpace their profitability.
There is this assummption that mainframes are ancient technology and are just dinosaurs waiting to die. I work for a company that is a large mainframe shop, and after checking out one of our 4 data centers, I was quite impressed with the technology involved in a modern mainframe system.
We have several processing boxes which are linked by fiber optics. They provide many different logical partitions (i.e. systems) which are dynamically allocated across the available CPU's. Kind of a cross between redundancy clusters and Beowolf clusters with dedicated I/O processors to handle the I/O requests of several hundred users.
While these systems might not beat out the raw horsepower of modern CPU's, the supporting communication and I/O bandwith cannot be beat.
Now let's have Mindcraft have a benchmark against a mainframe running Linux and the best NT system (I know...it's an oxymoron) out there, and let see what results they get...
This guy is bathering out his ass, and he gets moderated up because the Linux Everywhere crowd are such suckers that they'll buy the theory that Linux can replace OS/390. There's lots of 'informative' posts in this thread, but this sure isn't one of them.
I work in one of the indutries that you mention, and things like this fuel fantasies of overturning the Microsoft bought-out world where I work and installing Linux. Those people on production support, network admins, etc. would love me!
Please don't kill my dream!
And we're putting gigabit Ethernet interfaces on ours...
IBM has not sold AIX for the Big Iron for a long time. The current UNIX for the IBM mainframe is OS/390.
My sig is wonderful. I love my sig.
OS/390 is NOT UNIX
I went to the website. All I found out is that these machines have a bunch of processors, and they run at 637 MHz.
What the hell are they? PowerPC's? If not, won't IBM have a hell of a time porting glibc, gcc, binutils, XFree86, the kernel, etc. etc. etc. to the new CPU and architecture. Are they going to get SMP running? Methinks that's a hard task.
By the time they get done porting Linux, it'll basically be a new operating system.
I'd like to see it, but it seems like a lot of work for very little profit.
I worked in a fortune 500 data center for 3 years and though I wasn't monitoring the MVS consoles I can tell you that unscheduled IPLs (reboots) happened more than people probably think. Maybe the mainframe guys at that shop weren't so great or something but it seemed to me that the we averaged about one or two IPLs per week. That's among 2 separate S/390s with 3 LPARs per machine in a 24/7 operation. Not that great.
As for your list of problems:
The Big Iorn is back! MVS will still be there as it is THE most robust and secure operating system in existance. Liux on s/390 will seriosly rock.
'Do...
It's a dangerous trend on /. and the people in charge don't seem to notice it.
And if you consider the version running under VM (VM/Linux? Linux/VM? ye gods..)...
rms will probably ask you to call it VM/Gnu/Linux or Gnu/Linux/VM
;)
"The obvious mathematical breakthrough would be development of an easy way to factor large prime numbers." Bill Gates,
Spekaing of the 1970s and the wheel of reinvention, the virtual machine research at stanford that led to VMWare was named "Disco". Get it? Check out the paper: http://www-flash.stanford.edu/ Disco/sosp-html/
IBM's newer mainframes are all pretty standardised, consisting of multiple Power or PowerPC cores linked together.
No, I'm not talking out of my ass. I worked at a shop that was an ideal IBM shop (running OS/390, CICS, etc.) and were trying to implement Java (E-commerce and EJBs). IBM kept giving us the run around on Java support and OS/390. Our feeling was that they don't want to support it. If they open the door to Java-land, then why use IBM servers? Unless of course, they beat the crap out of everyone else's Java implementation.
We eventually went with Sun's E10k servers. We tried, but IBM basically just said that Java was not meant for their high-end machines. In personal computing and maybe RS/6000 land, Java is not deemed as a threat, but as far as enterprise level computing goes, they are SCARED or clueless (your pick).
I also said that chances are that it will not replace OS/390. See the post from the guy who has talked to the Linux/390 developer. It'd be nice if they ported CICS and VTAM (and everything else) to Linux. But, it ain't going to happen. They have too much invested in them to let them walk to another OS. IBM may release Linux/390 so that in our case where we want to use our IBM hardware we can use *different* software that is not part of the OS/390 fold, but is supported by Linux (et al).
Later,
Justin
Mu. P.S. The address you see is real. =)
one minor niggle. XFree86 is overdue for a rename. In fact, I think the developers have taken to calling the forthcoming version XFree 4.0.
The XFree codebase is used on x86, m68k, PowerPC, Arm, Alpha, MIPS and Sparc (with whatever grphics hardware is relevant).
eg. XFree was ported to the Amiga m68k platform when linux was pre 1.0 , AFAIK
Some intern in Toronto did this last summer. I heard it wasn't an official project. I remember reading some comments on it either here or in one of the newsgroups.
The danish mag Computer world had an article about a month ago, that mentioned that a lot of the "old" style I/O processors in the big iron machines are being released in new "quick/lite" versions attached directly to the system bus of the S/390. Making the "adapter" interface look more like the ones found in a "normal" *NIX box (PCI/MCA/PCx/...). Making drivers should be a lot easier with these new adapters. The artcile mentioned a Gigabit LAN controller that has already been released.
The article also mentioned that IBM has discussed the Linux port project with Linus.
Tom
Is that for the component that actually implements the virtual machines, or for the OSes that run on the virtual machines, e.g. CMS (was CMS ever capable of booting as a single-user OS on a "raw" S/3x0?), or the regular IBM OSes (or non-IBM OSes, as per the topic of this thread...) that can also run as guests in a virtual machine?
As VM implements a virtual, err, umm, S/3x0, complete with channel controllers, simulated mainframe-flavored disks, etc., and, I think, depends on features of S/3x0 to provide that emulation, it probably couldn't be ported at all easily.
However, VMware implements a similar type of "virtual machine" on NT or Linux on a PC. (The posts asking whether VM was like VMware were somewhat amusing, given that VM/3x0 and CP/360 antedated the 8086, much less VMware, by many years, as in "probably around 15 years, if not more".)
cute ain't it... I've seen that little trick too. They claim it's cheaper to use the same MCM in variety of boxes and control the performance by software then it is to develop custom MCM for each configuration. I beleive them; and besides... "MIPS on Demand" is a damn cool concept.
:)
and to really diverge... remember that in X the client-server division is backwards... that "regular old X-client" is really a server (ala XFree) providing GUI services to the window manager and other X clients you're running on the mainframe. But, again... why?
Look here http://www.chips.ibm.com/news/1999/s390/s390.html
The processor instruction set is a super-set of the ones found in PowerPC (I think).
- Extract from link above
IBM returns with the enhanced, copper-based S/390 G6 that can run at more than 1600 MIPS. By incorporating copper wiring, IBM's chip designers increased system performance, nearly doubled the number of transistors and added two additional processors to the G6's multichip module (MCM) -- without increasing its size. The MCM for the S/390 G6 Turbo server features 31 chips, including 14 microprocessors, representing nearly 1.4 billion transistors wired onto a five-inch-square ceramic substrate.
- Linux/390 Hmmm
Tom
Let me suggest that some of the confusion about the nature of "mainframes" can be cleared up by thinking of mainframes as giant servers designed for i/o intensive operations like, for instance, printing a whole month's telephone bills for several states.
Linux in a VM/390 environment is very promising, and would be even more promising if someone did a variant of XML designed to control 3270-family terminals which, if one squints a little, are not all that different from character-only browsers. As a native OS on the S/390 family, I've got my doubts; Linux doesn't currently support multi-processors well, and I don't know how it cope with the extremely fast parallel network that connects the 390 mass storage system. Still, IBM has people who've been working with those technologies for decades, so perhaps they know how to make it work.
When you intern with Ingram again next summer you might want to suggest they go back to Poughkeepsie and ask for a S/390 rep who isn't a fuckwit. IBM is backing Java on the 390 whole heartedly and with a vengance; Sun's slick marketing of the E10K lead a few customers astray and they're not just about to let the pile steal any more shipped MIPS.
If you take a good look around you'll see that IBM is the company with the single most to win/loose from the Java revolution, not Sun, not HP, not Oracle... IBM. They have the most disparate line of platforms, ranging from embeded systems running in your car to enterprise scaleable clusters that make your E10K look like an overpriced toaster - and everything in between. That is why IBM is kicking ass and taking names in the Java space... they simply have no other choice. There are more IBMers world-wide working with Java then there are employees of Sun Microsystems. IBM employs more people developping the Java platform than Sun. The fact that IBM isn't taking (or getting) much credit for that is hurting it's stock price and image.
(and no, I'm not the same person that posted above)
SGI and Sun have both made workstations based upon x86 that have no PC heritage, thank God.. anyone remember the Sun 386i?
Nope. It's a 16-general-register CISC instruction set (dating back to the early 1960's). The Linux on the IBM ESA/390 Mainframe Architecture page has a link to the the ESA/390 Principles of Operation manual, which describes the instruction set.
Quickly to answer: I have not worked with the S/390 series, but I have still seen a lot of old IBM iron. Never seen CMS running without VM. I have seen, however, VSE running without VM. And it seems to be quite a common setup, even though VSE on VM seems more common.
Not a scientific answer, but that's what I can give right now.
Hey, would you believe, I have a friend who had a 360 in the yard! I got some of those discrete (non-integrated) technology flip-flop boards as a souvenir!
I really appreciated this thread, made me remember the good-ol days...
Sigged!
Okay, while I was not the person who talked to IBM directly (gee, you went to my website, good for you!), my understanding was that he talked to every person under the sky about getting our system to work with Java. He talked to their marketing people who assured them that Java would be entirely supported by IBM. He then asked for an example (Alan Cox's "show me the code"). Their technical people failed to produce one line of code that would run under OS/390. Eventually after dragging several VPs on both ends into it, we finally got something running on the system (this was mid-summer). Mind you this was on their beta OS running on a test proc. slice - we needed this on our production environment by the end of the summer (a company that dependent on it is not going to run their production m/f on an beta OS - even IBM's). However, by now, I believe that IBM has officially released the OS version that supports Java natively (but I may be wrong - I am no longer at IM).
However, since we used CICS (as do most IBM shops), we wanted CICS/Java connectivity on OS/390. And, that was what ultimately killed it. While Java was technically supported by the OS, their killer app did not support it. What they said is that all of the COBOL would have to be rewritten to conform to Obj. COBOL standards, then the Obj. COBOL could call C++ wrappers which could then call Java (and that was only if we installed every beta they had). In something so performance driven, this was not an option (never mind beta code). We were trying to make this faster NOT slower. At the same time, we had to support the legacy COBOL code. Ingram has so much COBOL code that forcing a rewrite of any subset of the code becomes a logistical nightmare. We eventually settled upon having a J/Gate (Java->CICS) architecture. Far from our ideal, but at the time, it was our only option. IBM failed to deliver what their customer needed when they needed it. Now, in six or seven months, IBM may finally get their heads out of the sand and support Java in CICS in a reasonable manner. But, Ingram is now a lost cause in that respect.
So, to clarify my position a bit, yeah, OS/390 supports it. CICS doesn't. If you aren't using CICS, then why use OS/390? Yeah, DB2 and all of that is supported in OS/390, but IMNSHO CICS is still the lifeblood of the OS/390 series...
BTW, you are indeed correct, IBM's machines kick Sun's ass clear across the room. And, in a place where IBM has so much clout, they should never have let Sun in the door. Now that Sun has their foot in the door, some are seriously considering dumping all IBM products and turning into a strictly Sun shop.
Sun delivered, IBM did not. That is what matters in the end...
Later,
Justin
Mu. P.S. The address you see is real. =)
I must be thinking of another hi-end IBM system then. Yes you are right, the Power2 is found in high end RS/6000 systems.
Tom
and the moderation of this thread is another trend that's developing... the moderators that marked the original comment "insightful" obviously didn't read the article either. of course then someone marked the second response as falimbait ... which is true, but the comment was also 100% correct and thus hardly deserved to be a -1; and beign under that of course means that most of this conversation won't see the light of day.....
Um, I hate to point this out, but:
o Xfree86. It's just a name. You can run Xfree86 on anything if you *compile* it on it...
o "...written for the VM which hides the actual hardware from the programmer"... Not really a true statement: the virtual machine that it presents is a REPRESENTATION of the ACTUAL underlying hardware, i.e. you program it EXACTLY the same way you program the underlying hardware.
While mainframes may not have "conventional" (i.e. one chip) CPUs, architecturally they are virtually identical, as are most commercial machines (e.g. memory, registers, PSW, etc)
Err, umm, once upon a time, mainframes were one of the few sorts of "normal computers" around. They don't look like PC's, but PC's are the only type of "normal" computers if you take "normal" literally, as in "average", as in "the average computer, by sheer numbers, is probably a PC" (I neglect embedded systems here, which I suspect may well outnumber even "IBM-compatible PC's").
The S/3x0 instruction set is pretty conventional - 32-bit, 16 general registers, register-register/register-memory/memory-memory instructions, most of which are boring old load, store, add, subtract, multiply, divide, etc., with various more exotic add-ons. Just because something's a mainframe, that doesn't mean its instruction set and CPU are immensely exotic.... (The Burroughs mainframes, and their Unisys A-series successors, have a fairly exotic instruction set, but IBM mainframes don't.) The ESA/390 Principles of Operation manual documents the S/390 instruction set.
If by "the VM" you mean "VM/390" or whatever it's called these days:
Perhaps you're thinking of System/38 and AS/400, where the compilers used by application programmers don't generate native machine code, they generate code for a virtual machine, and the low-level OS code ("system licensed internal code") translates that code into the native machine code for the particular machine, if it hasn't already been done, in order to run it (that native machine code being a System/3x0-like instruction set on older machines, and an extended flavor of PowerPC on newer machines).
A port is in progress, according to the Linux on the IBM ESA/390 Mainframe Architecture page. ("A port of glibc has been started. System calls work. Signals don't.")
Perhaps porting the X server code would make no sense (although there do exist graphical terminals for mainframes - I think they're still used for engineering and scientific work), but the X client code might be useful.
As far as I know, "SMP", meaning "symmetrical multi-processing", as in "multiple processors, without particular processors being devoted to particular tasks such as 'one processor runs OS kernel code and another runs user-mode code' or 'only one of the processors is allowed to ever run kernel code' (as opposed to, say, a single kernel lock allowing only one processor at a time to run kernel code), has, as a term, been around longer than have SMP systems with Intel processors. SMP systems, whatever they've been called, have definitely been around longer than have SMP systems with Intel processors....
Indeed? If so, then those "Power or PowerPC cores" are presumably interpretively executing the System/3x0 instruction set, which is not, and has never been, a derivative of POWER. (POWER and its descendants are load/store 32-general-register RISC architectures; S/3x0 is a 16-general-register CISC architecture with register/memory arithmetic instructions.)
S/390 hardware hasn't been 32 bit for quite awhile... there are some dedicated chuncks that do 1Kbit (yes, 1024 bit processors), but I think most is 64 bit.
double-precision shift instructions,
Dude, what the f**k is a double-precision shift instruction??
I mean, do you just mean that you can shift up to 64bits? (that's what I would guess from the conetext).
--
"Subtle mind control? Why do all these HTML buttons say 'Submit' ?"
ReadThe ReflectionEngine, a cyberpunk style n
Little anecdote on S/390 processors. We run a 2003-205 S/390 box. Came with 1 processor, running 13 MIPS. We found it to be too slow, so we ordered an upgrade to a model 207 (24 mips). Cost 60K. The tech came in one night, put a floppy in the hardware console (it is an IBM pc, P-II/300), fiddled a bit, and viola! It was now a 207!
I queried this guy a bit on this black (blue?) magic. Seems the 200x series processors come with 6 CPU's in them. The clock oscillation rate of each, and the number that actively process are controlled by SOFTWARE! These things can be 6-way SMP, and over 140 MIPS by doing the same procedure... oh, yea, and forking over mega-bucks to big blue.
What an incredible business model! My (red) hat is off to the guys who came up with *that*.
That aside... I agree with another poster that Linux would be a damn sight better than the OE shell and Unix system Services. And yes, you can run the X server on the mainframe, and use your regular old X-client. But, again.,.. why?
Jim.
Wakko Warner wrote: Actually, there's kind of a fallacy operating here. Mainframes date from the era when there were only mainframes. They were expensive and big because computers were expensive and big. I remember the end of that era clearly; I was there.
Minicomputers followed. They were somewhat less expensive and newer technology. In theory, a very complete set of applications could have developed for minicomputers, and in fact quite a few applications did, but it became a marketing war, and the pitch was that somehow minicomputers were less capable than mainframes. It was an effective pitch but really there was a lot of marketing hype there.
Finally, as "mainframe" manufacturers began to develop a lot of the same newer technology to keep up with "minicomputer" manufacturers in terms of cost and size, the "personal computer" came along and threw the whole equation into a cocked hat. PC hardware certainly was initially less capable than mainframe hardware; the processor architecture featured such ancient constructs as an accumulator. Missing were things like orthogonal register sets; clean, simple instruction formats; end-to-end error correction.
But nothing said that PC hardware had to be less capable than mainframe hardware; it just didn't matter that it was, since it was inexpensive enough to be bought by multiple users in multiple departments. This allowed departmental users in the corporate world to bypass the huge project backlogs that most IS departments had developed and gave control of much more computing to those departments.
By the present day, it's clear that most computation is done on platforms that are considerably more powerful than the first PC's, but are descended from those platforms. It's also the case that more and more features originally found on mainframes are making their way to PC's, and this trend is likely to continue.
PC variants (not necessarily on Intel architectures) represent "where it's at" because anybody can buy them and stage them for particular applications. They're cheap and easy to operate. So they are certainly likely to accumulate a very rich feature set as time goes on.
The "mainframe versus personal computer" war has never been about hardware capabilities, per se. It's always been about who has control of computing, and clearly the PC won that war. At this point we can regard mainframes such as the S/390 as being relatives of PC's, in that they have to compete in the market to perform the same tasks that PC's routinely perform.
There is a not a UNIX box in the world that can match the stability of an IBM mainframe. UNIX (or NT for that matter) is not, will not and can never be as stable as an IBM mainframe running its classic and extremly evolved operating system. Running UNIX inside a virtual machine makes sense and is a natural evolvement of the platform.
SMP is NOT an intel thing. IBM's been doing SMP on Mainframes in various forms long before Windows was a twinkle in Bill Gates' eye. You think clustering is new, OS/390 can cluster up to 32 machines, each with up to 1600 MIPS each. Now that's POWER.
but the real question is does it support EBCDIC?
Given that the only "emulator" I saw mentioned in the article was for AIX, and that by AIX they probably mean AIX for RS/6000, and that most if not all current RS/6000's use the PowerPC member of the POWER family of architectures, and that Linux also supports PowerPC, that's possible.
However, what the article said was:
(emphasis mine). That suggests that there's no ABI compatibility involved, just API - Application Programming Interface - compatibility.
In any case, the only ways to provide the ability for IBM mainframes running OS/390 to run Linux binaries would be
IBM already have "a POSIX to OS/390 translation layer", in a sense - they have a UNIX-compatible environment, in the sense that it passed the UNIX 95 test suite, so at least some programs can presumably be recompiled to run in that environment...
...as long as they, say, don't assume that the characters "A" through "Z" or "a" through "z" are encoded as a contiguous set of values; their UNIX environment uses EBCDIC, not ASCII, as its character set. (Here's the home page for the OS/390 UNIX System Services.)
I infer from the article that part of the rationale for a Linux/390 port is to make it easier to port applications from UNIX environments - OS/390's UNIX environment may not be enough like "Real UNIX", implemented, as it is, atop a different OS, and using a different native character set, and so on, to allow quick porting, whereas Linux systems look enough like "Real UNIX" to me, at least, for me to consider them to be "Real UNIX", even though the Open Group don't yet have any Official Certification Results for any Linux system but do have one for OS/390.
I'm a VM and VSE systems programmer, VSE is not necessarily unintuitive, it just takes a little getting used to. It is certainly no more unintuitive than *NIX.
that stings nearly as much as when slashdotters insist that VMS is just like NT!
I was once told by an IBMer out of Boca that they were developing OS/2 on a mainframe like this. This was bcack around 12 years ago and apparently you could say "IPL os2" and it would load an OS2 kernel. Having once worked in development at IBM can believe they would do this.
My office mate at Team One was one of Amdahl's kernal hacks, circa 1991. Amdahl got Sys V going under VM. Very cool thing, since he could have multiple instances of UNIX running under VM, and diff them to see the results of his code mods.
Today, running Linux under EROS would be the best of *all* worlds, if only Linux had a decent GUI.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
VM beats *every* UNIX all to hell when it comes to reliability.
Running Linux under VM, is like running NT under VMWare. It lets the unreliable code run in a safe, isolated compartment.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
I don't think they have. AIX is for RS/6000 and the like.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
I Win!
This is just the kind of thing Linus was talking about during his keynote, the ability of Linux to scale not only to small systems but also large ones. Quite impressive having such an adaptable OS. Emulating it, not quite shure if that is as impressive. Wouldn't it take away from the power of a direct port?I wonder what uses this could bring if it has been ported... hmmm
_joshua_
Not too many years ago, IBM was considered the great Satan of the computer industry. My, how perceptions change.
I personaly am pleased that a Linux port can be used on the S/390... mighty impressive and a feather in the cap to all that made this possible.
And in the end, the love you take is equal to the love you make
If this is true (highly doubtful), this would definitely send shockwaves throughout the enterprise class server industry. If IBM believes Linux is ready to run on their heavy metal boxes, then some serious (re)consideration of Linux is going to occur in the next few months.
However, after personally seeing IBM run away from Java on the mainframes (running OS/390-MVS), I have to doubt this is true. IBM looked scared to death of Java on the mainframes. For the personal computers (i.e. with Jikes), they really seem to embrace Java, but on their enterprise class servers, they seem to be frightened to death of it. After all, if they support Java, then why not just use Sun boxes? Of course if they do such a thing, they'd have to do it better than anyone else (including Sun) - not to say that they aren't capable of this, but they'd have to try really hard. =)
This could also mean the beginning of the end of OS/390 (MVS) - maybe IBM finally decided that they no longer want to mess with having to recompile or support weird programs on their OS. Just give them a little VM (or actually processor slices most likely) and let them run their own little OS that will allow them to run their weird apps. Keep all of the VTAM and CICS stuff under OS/390 though. I'd be pleasantly shocked if they came out with full-blown support for Linux though... Oh, man, CICS Server on Linux/390 - oooh, wow - there would be a lot of people jumping into to learn Linux really quickly if that happened.
But, rumours are rumours for a reason. I'd be curious to know whether Linus knows about stuff like this - would a company tell him that they were porting Linux to XYZ hardware platform?
Later,
Justin
Mu. P.S. The address you see is real. =)
It's amusing to me, anyway.
Let's see...
Here it is: Linux on the IBM ESA/390 Mainframe Architecture
/cj
Of course you're right. By 'normal' I really meant 'commodity'. Mainframes are quite dissimilar from the desktops or workstations that most of us are used to.
Perhaps porting the X server code would make no sense (although there do exist graphical terminals for mainframes - I think they're still used for engineering and scientific work), but the X client code might be useful.
Indeed. But the only really interesting part about porting X would be the server side. The server side has to interface with graphics devices. I haven't looked at the XFree codebase, but I presume that there's very little platform specific code in the client.
As far as I know, "SMP", meaning "symmetrical multi-processing"
I believe that this was a term introduced by Intel, and I don't think that other multi-CPU architectures are described with this acronym, but I could very well be wrong. I also believe that the 390 architecture is massively parallel but not really symmetrical. As another poster mentioned that the 390 can have various CPU modules which might not even run the same instruction sets.
are you sure you aren't thinking about the AS/400? (hint: it isn't a mainframe.)
:)
the S/390 uses the G5 or G6 chips (be sure to check out the images link on the upper right... intel bunny suits eat your hearts out
the AS/400 uses a cousin of the PowerPC chip; and was in fact the first IBM product to use PowerPC based technology over five years ago.
the RS/6000s use PowerPC as well as PowerRS chips such as the Power4.
2.I doubt that "most mainframe programs" are written for it - the programs that run atop VM are largely OSes, and the applications are
presumably written for those OSes (OS/390, ESA/VM or whatever DOS/360 turned into, etc.).
Actually, VM is a complete OS, with tools, editor, compilers and applications deisgned specifically for it. I have done some little developement on VM. It's true that the company where I worked used VSE/ESA over VM for their production mainframes, but that doesn't have to be necessarily so. And actually, I personally hated VSE/ESA. It has a lot of features, but it's so friggin unintuitive. I have never seen anything so incompatible with human brain as VSE. VM, on the other hand, is was much clearer and simpler for me. I would accept a job of VM software developement anytime (if it payed better than the current one).
Actually, what do you think, would it be possible to port VM to anything non-mainframe? (a PC, for example?)
----
(I have 5 or 6 VSE/ESA student manuals. Anyone interested? I would gladly trade them for an old AHA 1540 or other ISA SCSI adapter)
----
Sigged!
IBM lost their ability to force anyone to use their products. That's why notbody hates them today.
Now, back in the day, IBM would happily rat you out to your boss if you bought DEC, or if you did anything else that wasn't toeing the party line, but even at their worst, they were never as arrogant as Micro~1.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
Possibly, but I seem to remember hearing the term before x86 MP systems were common (although they date back at least as far as the Sequent Symmetry, so they do go back a while).
Perhaps Digital^H^H^H^H^H^H^HCompaq don't say "SMP", but they sure say "symmetric multiprocessing" (admittedly, not "symmetrical", if one wants to be fussy) on the Digital^H^H^H^H^H^H^HTru64 UNIX home page.
There exist S/390 machines that have a lot of processors, but the Multiprise 3000 "enterprise servers" (every time I hear some marketoon say "enterprise", I wonder whether they intend to install the "enterprise" product in question on the bridge of NCC-1701) start out as uniprocessors and go up to big honking two-way systems.
I also have the impression that the MP S/390's are "really symmetrical", in the sense that there aren't particular S/390 processors dedicated to specific functions.
I suspect he's thinking of I/O processors, e.g. the processors that run the channel controllers (which I wouldn't be surprised to hear were PowerPCs these days), the communication controllers, etc. - the processors that run the applications, and the bulk of the OS, are S/390s, as far as I know.
Some PowerPC chips are Symmetric MultiProcessing
(with the notable exception of G3s (PPC750s))
actually they're up to the Power3 now... expect the Power4 to replace that sometime next year with it's awesome technology.
an IBMer requested to change autoconf so it find out what OS the s/390 machine is running, so they obviously have this working. read the autoconf mailing list to see, it was a longish post.
I reported this story to Slashdot over 6 months ago. I was on a high profile team at IBM and the project leaders for this porting effort asked us if anyone wished to join the development team for porting Linux to S/390. It's no bull people, IBM is adopting Linux in a corporate sweeping manner.
-Rusty
The Master (Angelo Rossitto) in Mad Max Beyond Thunderdome, "Not shit, energy!"
The old UNIVAC 1108 sold a *lot* of copies before UNIVAC's mgmt (Rand? Remington?) realized there actually was a demand for computers.
So, they rolled out the 1106 computer for less than the cost of the 1108 (the development costs for which had already been amortized) which only had a clock-card (and badges) different between the two machines (some time later the 1106's were their own machines, but the first cut was a downgraded 1108).
If you look at IBM's licensing issues for ADSM (on AIX/NT, maybe MVS) it seems that you can license it w/o paying for it- which is, in it's own way, true. If you've exceeded the nominal license, however, you may have problems getting serviced...
I don't think companies with their businesses dependant on these machines will be in a hurry to exceed their service contracts...
Ya gets what ya pays for- but you also pay for whatcha get...
-soup (GNUrd, Speaker to Machines) "Laugh at yourself- Why should everyone else have all the fun?" -Romanchek's 6th Ru
This has been done on the IBM ESA/390. See the Linux on the IBM ESA/390 Mainframe Architecture project. Unfortunatly it's still in devlopment. So no banks will be using it. :-)
And there is a project looking at the possibility of a AS/400 port. It's not even in development though.
About 6 years ago I saw a version of AIX Unix running on a IBM mainframe under VM. It was interesting, emulated a powerpc based RS/6000, as I recall.
I could believe that they might have a version of Linux running under VM, using some of the same tech they developed for that port of AIX.
But I don't see too many people with spare 3090s sitting around wanting to run Linux.
I work in the mainframe world and although we run MVS, I have seen references to IBM running Unix on their S/390 line (maybe others). So, it shouldn't be too hard for them to get Linux to run too. Someone posted something about TCP/IP and seemed suprised it might be on a MF. Well even on our MVS box we use TCP/IP for everything. We even have SMTP and FTP servers running on it and it works great. I think it would be wonderful to have Linux as the base OS.
--Scott 8-}
..they're minicomputers. That's not just a nit-pick - programming for a mainframe, at least at the lower levels, is much nastier than on the relatively uniform minicomputer architecture. A mainframe feels closer to a tightly integrated network of special purpose devices than a single CPU system.
From a programming perspective, a VAX is much more like a souped up microcomputer than a mainframe. One reason why virtual machines are popular on mainframes is that they hide the really ugly parts of the system; not just from application programmers but from kernel programmers.
I can believe a Linux port to VM, but I'm much more skeptical about a port to the bare metal.
Caveat - my mainframe penance was on Unisys machines, so correct me if I'm off base about IBM's big iron. No such doubts about the minicomputers though.
This is Old News, in computer terms.
LinuxToday ran a story on this back in mid-October. In it, they referenced an article in the Danish version of ComputerWorld. The feedback comments to LinuxToday are interesting, and several of them pointed out one project's home page.
dragonhawk@iname.microsoft.com
I do not like Microsoft. Remove them from my email address.
I am a Systems Programmer for a community college. My supervisor (the Lead Systems Programmer) just recently told me that an IBM systems engineer told him that a port of Linux for the 390 was in the works to be officially released the end of 2000. This would be a SUPPORTED product, apparently.
Things to remember about mainframes. There are a myriad of OS's that run on one box at a time. Big banks and big corporate outfits traditionally run
MVS, which is a beefier (more expensive) OS. Colleges (or other institutions that need mainframes but are a little short on cash) usually
run VM. There is a Unix OS available that goes along with MVS, but according to my boss, the Linux for 390 will be targeted more towards those running VM.
A slip of the foot you may soon recover, but a slip of the tongue you may never get over. -Benjamin Franklin
Instead, we have classic FUD: press releases reporting rumours of what IBM may or may not be doing. Stuff designed to scare away contributors and supporters of the legit, above-ground, out-in-the-open development of the Linux Mainframe port.
Don't trust anyone over thirty [employees] !
This would be cool! I've ben working on IBM mainframes for five and a half years now - under VM, MVS, and OS390 operating systems.
It would be interesting if IBM took a spare mainframe, loaded Linux up on it, and connected it to the web for the OSS community to play with, experiment with, and tweak. I wonder what kind of performance scores Linux would get as compared to OS390 or IBM's other mainframe OSs.
Did IBM just decide that AIX was a bad dream and it's time to wake up now...
were true why in the world would IBM replace AIX on their Big Iron? Linux is a nice OS that is finally getting some attention but maybe it's getting a little too much. It's at the point now where everyone has a Linux .plan so they can tout it for PR and then not really go anywhere with it. Porting Linux fully to their mainframes would require a huge rewrite of the kernel which would make it look alot like AIX. Whats the point of calling it Linux if you have to take out most of the kernel code to port it to the mainframe? PR dude.
I'm a loner Dottie, a Rebel.
What would the purpose of this be?
As the article says (you did read the article, right? *grin*), the main point would be to run Linux in parallel with other S/390 OSes like MVS. As everyone seems to be pointing out, Virtual Machines are very popular in the mainframe world, and it is quite common to run more then one OS at a time. Thus, Linux would be just one more OS.
The suggested application was Lotus Domino. I can also see web servers, application servers, general Internet servers, that sort of thing, being useful. Perhaps a company running a big back-end mainframe database would want to use Linux for the front-end interface, with (for example) Cold Fusion. I can see quite a few uses for it.
Is a big bank going to dump MVS and move to Linux on the S/390? No, of course not. That isn't the point.
Plus, there is hack value. We can now say with a fair amount of confidence that Linux is the most scalable OS on the planet. It runs on everything from large IBM mainframes to hand-held Palm Pilot devices.
I'll believe it when I see it.
It is already partly done, from what I understand. My comment here has links with details.
dragonhawk@iname.microsoft.com
I do not like Microsoft. Remove them from my email address.
Back in the day, Brown students used VM/ESA for
email. Some of the people who knew a bit about the OS figured out that you could load a different "OS" by typing IPL "OS name" OF course, the only one you could load was ESA (or CMS).
IPL Linux was jokingly mentioned.
Maybe I'll be able to dust off my account and give it a try someday.
I think you may have the wrong idea on what they mean by "emulation" here. This is not the same as, say, videogame emulators, where you're emulating one machine on another, and as a result you spend alot of machine cycles emulating the other machine.
Rather, this is probably closer to how FreeBSD "emulates" Linux: It provides a compatible Application Binary Interface, and it just shuttles all the Linux system calls over to FreeBSD equivalents. A Linux emulator for OS/390 would probably consist of a special loader, and a POSIX to OS/390 translation layer. Depending on how it's done, it could be a reasonable environment, and not nearly as computationally costly as, say, emulating a full computer running Linux as a process on a 390 mainframe.
Someone whack me with a clue stick if I got any of this wrong. :-)
--Joe--
Program Intellivision!