Re: Java performance and integration

John,

Your last question first; at levels of the OS that have not been supported for quite some time, no one cares. If this discussion were about IBM i 6.1 or 7.1 different discussion so I will restrict my comments to the supported versions of IBM i. The galactic differences between V5R2 (I had to type that twice because V5R4 kept coming out of my fingers) and now are, well galactic in size.

The JVM on IBM i is as close to hardware as it can get utilizing the hardware in the most efficient manor available to the developers. That's why when the 64bit and 32bit JVMs are put in a real head to head test, IBM i almost always wins the battle given equivalent processor, memory, workload, etc.

Your discussion about QSHELL is again, old. While I strongly believe that IBM needs to upgrade PASE to a current version of AIX, it is a "native" command line I use almost all the commands that are available in AIX version in PASE, and you can add the ones that are not, ie: VIM.

It sounds to me like you need to start working on a more recent version of IBM i. Your questions will start to go away.

Jim Oberholtzer
Chief Technical Architect
Agile Technology Architects


On 7/11/2011 5:04 PM, John Yeung wrote:

I'm forking this off from the mammoth RPG400-L thread called "RPG -
I'm not dead yet!". The moderator requested the discussion be moved
to MIDRANGE-NONTECH, so here it is.

A couple of points from that thread that I wanted to continue, because
my knowledge is insufficient in these areas:

1. How "close to the metal" is IBM's JVM on the i? Apparently it's
pretty darn close, but that is not the subjective impression I've
gotten, from my (admittedly limited) use of it on V5R2. There was
another thread (I think on MIDRANGE-L) not too long ago from someone
asking if Java performance on the i has improved for 7.1, or whether
he should prepare to continue to be disappointed.

The thing is, on V5R2, it*feels* like RPG is blazing fast (well, as
fast as the machine can go), and Java is dog-slow. Then on top of
that, Java seems to need Qshell and PASE, adding a layer of
inconvenience, if not performance penalty.

2. Regarding Java's integration with the i; and how that compares
with Java's integration with other platforms: In my opinion, Java is
not particularly well integrated with any platform, in the sense that
no hardware or operating system that I'm aware of was designed
specifically to run a JVM. From the other direction, Java doesn't
seem designed for any particular hardware or operating system (it's
just up to the respective JVM implementors on the various platforms).

That said, it still*feels* to me like Java is integrated better on
other platforms, partly because of the Qshell thing I mentioned before
(on other machines with a JVM, Java lives in the "native" command
environment). Also in part there is the EBCDIC issue, which seems to
thwart practically everything i (not just Java), since essentially
nothing else in the world uses it.

In the RPG400-L thread, it was mentioned that IBM gave RPG some nice
hooks for Java that are perhaps better than what is available for
other languages or other platforms. But the trend in the rest of the
world seems to be to just accept the JVM itself as the platform, and
write languages that target it. (Except Microsoft, which developed
the competing .NET, which is roughly analogous to JVM.) Now there are
tons of languages for JVM (as well as for .NET), and these naturally
interoperate stunningly well. But to my knowledge, these are not
available for IBM's i JVM, because of the unusual architecture of the
i.

Am I wrong? Or perhaps does no one care?;)

John Y.