Duel Quad Xeon - Not Performing???

[TomElcott]

That is great news. Out of curiosity did the single quad-core have more RAM than 12GB?

Thanks

John

 

I never actually thought about that... But the single quad only had 8 gigs of ram...

[ihabkal]

"8 cores need more pumping of information than 4 cores to keep busy." so they need more ram, being faster and more performing double the ram wasn't enough.

[John.RenderStream]

I never actually thought about that... But the single quad only had 8 gigs of ram...

 

I know these kinds of issues are real hair pullers and maybe hurting your work personally and I'm terribly sorry about that but they are most intriguing too. I will go out on a limb and speculate what is going on.

 

The statement that these are big computational pipes so they need lots of memory to support them has merit but I think not because of added speed but because memory allocation and management by software and/or OS architecture. Here is my speculation (please take it as opinion and not fact):

1. The application is multi-threaded.

2. Each thread is blindly allocated memory so twice the cores take twice the allocated memory whether the thread uses the memory or not.

3. The allocated memory plus system overhead is more than 6GB and less than 8GB per four cores so it is more than 12GB but less than 16GB with two processors so 24GB fixes the problem.

4. While there is QPI between the processors so the possibility of shared memory exists the application and/or, remotely, the OS is not utilizing them so the dual quad cores are really acting like two computers on one board and not a unified system meaning that the memory managed by one processor is essential all it gets and that is 6GB.

5. When the memory allocation fails it defaults to single thread so utilization drops to 12.5% for the application.

6. The utilization for overhead including swap pushes the total number to 20% to 30%.

7. When running without proxies this is not the case because the application is tuned better for that function.

 

Again I will emphasize this is simply speculation based in case studies with other applications that I have read about but we have only circumstantial evidence so it's just a swag.

 

The net is for the moment you have a solution.

 

Best regards,

John

[F J]

Again I will emphasize this is simply speculation based in case studies with other applications that I have read about but we have only circumstantial evidence so it's just a swag.

 

John, i suppose ur theory sounds plausible..

i guess i would have to agree with ihabkal about the dual-quad system needing addicional RAM, but nowhere near the amount of several GB's..