Re: [Gems-users] Asymmetric Memories

[Greg Byrd <gbyrd@xxxxxxxx>]

So a cache needs figure out the address of the home node for a memory 
block, based on its addressed.  Without the uniform distribution of 
addresses, how would you propose to handle this in a real system?
You could have holes in the physical address space, I suppose, which the 
OS would know about and could avoid allocating.   (This is assuming that 
the "natural" mapping, with each module being assigned a fixed chunk of 
physical addresses.  In your case, you could assume 512MB per module, 
but the OS would know that the "missing" 384MB in your smaller module is 
not available, so it would never allocating anything to those addresses.)
Otherwise, it would appear to me that you would need some sort of table 
that gives the mapping of addresses to memory modules.  If that's a 
reasonable model of the system, then you could implement such a table in 
Ruby, and change mapAddressToDirectory accordingly.
...Greg


Héctor Montaner wrote:
> Hi,
>
> I have 4 processors with 1 memory module per processor. The thing is that
> I would like to have different memory sizes, for example, 128MB in one
> processor  and 512MB in the rest.
> The problem is that when a cache forwards a request to a directory, it
> uses map_Address_to_Directory (RubySlicc_ComponentMapping.h), and this
> function uses a set of bits in the address to determine the corresponding
> directory. This means that, by default, Ruby distributes the physical
> memory space in a symmetric way.
> Any idea?
>
> Thanks in advance
>
> Hector
>
>
>
> _______________________________________________
> 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.
>
>