HPUX on Itanium

[C R S]

I'm trying to find some info about compiling and running 32-bit applications that use Oracle on an Itanium server running HPUX 11.23.

we currently run on HP PA-RISC servers. I'm wondering how much of a perfomance change(good or Bad) we will see when we port to the Itanium. I've been getting conflicting reports on how well Itaniums run 32-bit apps.

We currently aren't ready to port our app to 64-bit but most of our customers prefer HP hardware so we are looking at Itanium.

Thanks for any info or documents that could help me out.

CRS

[Wim Rombauts]

One thing is that the current DC-Itanium processors are more then twice as fast as the fastest PA-8900 processor. Even is your 32-bit application is not performing 100% on Itanium, the is a certain performance gain.
If I am not mistaken, you could even try to run your PA-RISC application unmodified on Itanium, using the ARIES emulation software. This way you can probably already get a performance idea without too much effort.
A native Itanium recompilation will give a much better performance of course.

[rick jones]

The confusion likely stems from the FUD about running 32-bit _x86_ binaries on Itanium, which is only under Linux and perhaps Windows.

HP-UX provides support for native Itanium 32-bit binaries and they run just fine. There is no performance penalty for running a native 32-bit Itanium application under HP-UX.

The only wrinkle _might_ be if you link to Oracle libraries - make sure they provide native Itanium 32-bit versions.

Depending on how "clean" your applications are already the "port" to 64-bit might not be all that difficult. And given that 64-bit has been happening in HP-UX since 1997, it might not be a bad idea to get started :) There are some options to the HP compilers to get them to emit 64-bit migration warnings. That would be a good starting point I would think.

[Bill Hassell]

If you don't recompile at all and just copy over the 32bit executables, they will run under the ARIES emulator on Itanium. You can expect to see a truly compute-bound application (no I/O) slow down like in any emulator/interpreter. The general experience is that you'll see about 3x excution rate penalty. But if the application is a database app, the vast majority of clock time is spent waiting on I/O, whether it is getting records from Oracle or waiting for application files. That means that the slower execution time is generally masked by similar I/O time between PARISC and Itanium.

But recompile your 32bit apps on Itanium and yes, you'll see a dramatic increase in performance over PARISC, especially compared to pre-8800 PARISC processors.

[Dennis Handly]

The difference between +DD32 (the default) and +DD64 is composed of two parts. Using +DD32 causes extra addp4 instructions, possibly increasing instruction cache/TLB. Using +DD64 causes your longs and pointers to double in size, causing data cache/TLB issues.

In most cases, the increase in data size will cause +DD64 to be slower.

>Rick: There are some options to the HP compilers to get them to emit 64-bit migration warnings.

This is +w64bit. Or on PA, +M2.