Asking again about performance of 64-bit application.

[yck]

Hi all, i have make an experiment to compare performance between 32-bit and 64-bit application. However, i found that 64-bit performance is 1% slower than 32-bit on large data sets that runs for more than 30 minutes. Is this correct? What else to look out for?

What i really means is.. is that realistic that performance of 64-bit application is not much different compare to 32-bit application? I means speed of application (involve arithmetic computing). Cause from what i read from 64-bit article is 64-bit application have much performance compare to 32-bit application.

For your information, application that i try is involve with many number crunching, or arithmetic computing.

Anyway, information below this is configuration parameters for my HP machine:
maxdsiz 3221225472
maxdsiz_64bit 1073741824
maxssiz 83570688
maxssiz_64bit 8388608
maxtsiz 67108864
maxtsiz_64bit 1073741824
shmem 1
shmmax 1073741824
sema 1
semaem 16384
semmap 66
semmni 64
semmns 128
semmnu 30
semume 30
semvmx 32767

How can i determine which setting should be suitable for 64-bit application? Like where can i refer to?

And lastly, is that 64-bit application didn't have much performance compare to 32-bit application if main function of application is to make arithmetic computing?

[Rainer von Bongartz]

You will newer find much differences in the performance of 32 and 64 bit systems.
You will benefit from a larger address space on 64 bit systems (big files , more memory etc.) and from faster internal io , but the CPU computations will not see a real diffrence on 64 bit.

[Magdi KAMAL]

Hi yck,

have a look in :
http://devresource.hp.com/STK/64concepts.html


You may review your kernel setting as follow :

maxdsiz 3 221 225 472 -> Very large !! 100663296
maxdsiz_64bit 1073741824
maxssiz 83570688
maxssiz_64bit 8388608
maxtsiz 67108864
maxtsiz_64bit 1073741824
shmem 1
shmmax 1073741824
sema 1
semaem 16384
semmap 66 -> 512
semmni 64 -> 512
semmns 128 -> 1024
semmnu 30 -> 128
semume 30
semvmx 32767

Magdi

[Wodisch]

Hello,

if you do NOT have the need of the bigger address
space, you should NOT compile your programs for 64bit.
But you should use the PA-RISC 2.0 instruction set - if
possible!
The reasons are
- 64bit instructions are bigger (64bit) and hence need
more bytes to be moved from RAM to CPU, eating more
space in the on-chip instruction cache
- PA-RISC 2.0 has an improved instruction set
HTH,
Wodisch