[Q] Run-time perfomance is very slow in HP 64bit machine

[Kim Ji-Hoon]

I am developing applications in using c in the environment of HP 64-bit machine.

But, the binary compiled in HP 64-bit machine is much slower than other environments - for example, linux(intel machine), solaris(sparc machine) and other hp-ux (HP 32-bit machine).

About 10 times take.

I compiled with default compiler option. this is maybe what compile in 32-bit mode. I have to compile in 32-bit mode because the libraries linked are compiled in 32-bit mode.

6 cpus is equiped in the 64-bit HP machine and very powerful.

But, perfomance is not satisfying.

Why this happen?

Plz help me.

ps) I'm Koream. So, I can't write English well. Sorry for my crude english.

[Dietmar Konermann]

Hi!

You should really provide more details about your problem. "Much slower" is _far_ away from being precise enough to conclude anything.

What type of program? Source code available? What code paths are slower than on other systems?

Regards...
Dietmar.

[Stefan Farrelly · Accepted solution]

This is a known problem, weve seen the same here. Consensus is a performance loss of around 5-10% if running 32bit compiled binaries on HP-UX 64bit. The solution is;

1. Compile them to 64bit - if you can
2. Dont use 64bit HP-UX - install the 32bit version or else you will have to put up with the performance loss.

Remember, 64bit is designed to run 64bit programs - not old outdated 32bit applications.

[Dietmar Konermann]

Stefan,

just being courious... do you have some documents handy that explain this 'known problem'.? Never heard of that before.

Regards...
Dietmar.

[Stefan Farrelly]

Hi Dietmar,

There is an hp document about this somewhere....someone posted to the HPADM (dutchworks) list that theyve read it, but I cant find it now. The gist was that there may be a performance degradation when running 32bit apps on a 64bit OS.

There is some info here on an HP site here;

http://devresource.hp.com/STK/64concepts.html#AUTO13

The actual amount of possible degradation depends entirely on the application. In my experience at my current site, working for HP, its 5-10% typically, ocassionally more. In some cases we could get our application people to migrate to 64bit, and this fixed any degradation, and some apps we leave on 32bit machines. Here are a couple of earlier questions about the same thing - some of the replies are interesting;

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x5d7587dc4d7dd5118ff00090279cd0f9,00.html

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x9f7987dc4d7dd5118ff00090279cd0f9,00.html

[Dietmar Konermann]

Hi, Stefan!

Thank's a lot for that information.

Interesting is that your 1st link http://devresource.hp.com/STK/64concepts.html#AUTO13 argues the other way around... 32 bit often faster than 64bit, due to less overhead. Of course 64bit can boost applications that make use of the larger address space.

So in general one should answer with Performance Tuning Rule #1: "It depends."

But really important is, not only to compare 32bit vs. 64bit. We need to make sure that PA2.0 code is used for PA2.0 systems, e.g. using cc with "+DA2.0".

Regards...
Dietmar.