| View previous topic :: View next topic |
| Author |
Message |
sheepdog
Guru
Joined: 14 Oct 2002
Posts: 369
Location: Edison Enterprises Inc., Lake Oswego, Oregon, USA
|
 Posted: Mon Mar 08, 2004 4:26 pm Post subject: Optimizations |
 |
|
Just ported an application from AMD MP 2200 dual processor machine to AMD Opteron 246 single processor. The application is much slower on the new Opteron machine. 2 questions:
1) Will there be more improvement in speed by adding a second Opteron CPU (the motherboard is dual processor capable) or by upgrading memory from the current PC2100 to PC4000?
2) How much experience do we have with using compiler optimizations -O3 instead of -O2? This application's speed has been improved by the -O3 optimization on the old machine. Has anyone built and run an Opteron system with the -O3 optimization? |
|
| Back to top |
|
 |
brad_mssw
n00b
Joined: 24 Dec 2003
Posts: 29
Location: Alachua, FL
|
| Posted: Mon Mar 08, 2004 4:32 pm Post subject: |
|
|
-O2 will usually be faster than -O3 on AMD64.
Adding a second processor will only speed up your application
if it's multithreaded or spawns multiple processes, otherwise
you have no way to benefit.
Also, I'm not aware of anyone running PC2100 ram in an
Opteron system, I'm surprised it actually works. You should
be running PC3200. Most likely you system isn't meant to
operate with ram at that slow a speed, so it could slow your
system down more than just the ratio of the speed of the ram.
-Brad |
|
| Back to top |
|
|
sheepdog
Guru
Joined: 14 Oct 2002
Posts: 369
Location: Edison Enterprises Inc., Lake Oswego, Oregon, USA
|
| Posted: Mon Mar 08, 2004 4:42 pm Post subject: |
|
|
| brad_mssw wrote: | -O2 will usually be faster than -O3 on AMD64.
Adding a second processor will only speed up your application
if it's multithreaded or spawns multiple processes, otherwise
you have no way to benefit.
Also, I'm not aware of anyone running PC2100 ram in an
Opteron system, I'm surprised it actually works. You should
be running PC3200. Most likely you system isn't meant to
operate with ram at that slow a speed, so it could slow your
system down more than just the ratio of the speed of the ram.
-Brad |
Yes, the application is very much multithreaded.
The motherboard is Tyan Tiger K8W and PC2100 ECC Reg memory is recommended and works fine. Fortunately, since I didn't have to buy more memory to change the motherboard/CPU. But I will understand your answer to mean that upgrading memory would have a greater impact than another CPU.
Good to know about the -O2-faster-than-O3 paradox. Very unexpected. |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
|
Gentoo on AMD64
