Aries software emulation

[Rainer von Bongartz]

Can anybody share some experience using the aries software to execute PA-RISC software on Itanium?

do applications really run

1) transparently
2) accurately
3) efficiently

as promised by HP ??


Regards
Rainer

[Keith Bevan_1]

Rainer,

Below is a url to the document(s) that may assist in answering your questions.

http://csdl.computer.org/comp/mags/co/2000/03/r3047abs.htm

Keith

[Sundar_7]

Hi Rainer,

I dont have any experience with Aries - but with little knowledge I have, it is not recommended to use Aries with applicatios where performance is a concern.

-- Sundar.

[A. Clay Stephenson]

The vast majority of PA-RISC works perfectly and transparently.

The downside is that there is a approximately a 3x-5x CPU performance hit. CPU intensive applications (e.g. CAD, Finite Element Analysis, and simulations) are not good candidates for ARIES but because most UNIX applications are IO rather than CPU bound, the overall performance degradation can be almost nil. It really depends upon what you are trying to do.

[Arijit · Accepted solution]

Hi,

To take each point at a time:
do applications really run

1) transparently
Absolutely, the IPF kernel detects a PA binary and invokes ARIES. In fact what most people don't realise is that every IPF machine has a lot of s/w running through ARIES because of its transparency. ( an IPF system cannot be brought up in HP-UX if aries is not there)

2) accurately
ARIES has been tested with various kinds of applications such as Apache webserver, Unigraphics modelling suite, etc. Big customers like NRI Data systems, Telcordia etc use ARIES for a host of applications. And ARIES is a fully supported product from HP, so if you run into trouble with your app, you can get help.

3) efficiently
ARIES efficiency depends purely on type of application. As pointed out earlier, an I/O bound process will see very little degradation.In fact some customers have been known to get better performance than their PA systems because the IPF system architecture is better than some older PA systems.
CPU intensive multithreaded processes will run 2-4x slower and pure FP apps slowdown by 3-6x.
On an average you should get the similar performance as a PA8700 system.

[Gregory Fruth]

The other posters' comments are all quite
accurate. One thing to note, however, is
that you CANNOT mix PA-RISC and IA64 objects
in one executable. All code in the
executable must be PA-RISC in order for it
to run under Aries.

Therefore, the app must link to PA-RISC
libraries only. If the app links to
shared libs that's OK, because HP-UX 11.2x
comes with various PA-RISC shared libs like
libc and libm.

Also, the IA64 compilers don't support
cross-compiling for PA-RISC, so if the
app is partially compiled at run
time it will NOT run under Aries as-is.
You'll have to modify the app so that
all the compiling is done on PA-RISC.

HTH

[doug hosking]

I pretty much agree with the previous comments. The thing to keep in mind is that Aries is largely a transition tool. I don't think you'll hear a lot of people suggesting that you never migrate your applications to run native on IPF if you have a reasonable choice. What Aries does is let you do that migration gradually, on your own schedule, instead of in crisis mode all at once. If, for whatever reason, you have difficulty migrating an application (third party, lost source code, bankrupt vendor for some key element of your solution stack, etc.) you can still use your IPF systems, though with some performance penalty for the emulated code.

Aries isn't perfect, but it's definitely more than good enough for lots of purposes. I run a number of PA binaries on IPF systems just because Aries runs well enough that it isn't worth my time to rebuild them.

I've been happily running a PA emacs binary that I last recompiled in 1994 for HP-UX 9.04. Aries is quite happy with it on all supported IPF versions of HP-UX, and I don't notice any slowness in interactive response, even though I do a lot of editing with it. I'm sure if I actually measured CPU time I'd see some loss, but it's not enough for me to care about.

If you look at Aries from that frame of mind, I think you will be quite happy with it. If you run CPU intensive applications 23 hours a day and think you'll never need to rebuild them to run native, you might need to reset your expectations.

Overall, I'm more than happy with how well Aries works. The fact that I simply don't think about it very often says a lot about how transparent and reliable it is in real life.