Re: [Gems-users] L2 cache banks question

[Dan Gibson <degibson@xxxxxxxx>]

Since you're running 32 cores, I would expect that ocean fits entirely 
in the L1D caches, unless you've made ocean's working set large or the 
caches small. If ocean resides in L1s, then the L2 performance isn't 
very critical.
Ocean's working set (assuming N = matrix dimension):
(N+2)*(N+2)*(sizeof(element))*2 copies
For 66x66 and double-sized elements, this comes out to 69kB. Divided 32 
ways thats ~2kB.
For 258x258 and double-sized elements, total size is about 1MB. Divided 
32 ways ~32kB.
The default L1D size in Ruby is 64kB.

Regards,
Dan

Filipe wrote:
> Hi!
>
> I have a question about banks with the MSI_MOSI_CMP_directory and the 
> MOESI_CMP_directory...
> I did some tests using 4, 8 and 16 banks with both protocols and an L2 
> cache with 16MB and 8MB...
> The CMP has 32 cores accessing the L2...
>
> For SPLASH2-OCEAN, I got similar results for each protocol... these 
> are the execution times in cycles...
> MSI:
> 110681587 - 16MB - 16 banks
> 110882613 - 16MB - 4 banks
> 110007560 - 16MB - 8 banks
>
> 112847680 - 8MB - 16 banks
> 115278293 - 8MB - 8 banks
> 114196480 - 8MB - 4 banks
>
> MOESI:
> 91810800 - 16MB - 16 banks
> 90638080 - 16MB - 8 banks
> 91811853 - 16 MB - 4 banks
>
> 91366667 - 8 MB - 16 banks
> 90484880 - 8 MB - 8 banks
> 92219093 - 8 MB - 4 banks
>
> the differences are less then 5% in each protocol... is that correct? 
> why is it so small?
> is the number of banks too small for the number of cores?
>
> I would appreciate any kind of help to understand this.
>
> Thank you  very much!
>
>
> --
> Filipe Montefusco Scoton
> ------------------------------------------------------------------------
>
> _______________________________________________
> Gems-users mailing list
> Gems-users@xxxxxxxxxxx
> https://lists.cs.wisc.edu/mailman/listinfo/gems-users
> Use Google to search the GEMS Users mailing list by adding "site:https://lists.cs.wisc.edu/archive/gems-users/"; to your search.
>
>   
--
http://www.cs.wisc.edu/~gibson [esc]:wq!