Re: [Linux-ia64] Re: [Discontig-devel] CLUMPS, CHUNKS and GRANULES

[Jack Steiner <steiner@sgi.com>]

> 
> >> > - A contiguous group of memory chunks that reside on the same node
> >> >   are referred to as a clump. Note that a clump may be partially present.
> >> >   (Note, on some hardware implementations, a clump is the same as a memory
> >> >   bank or a DIMM).
> >> > 
> >> > - a node consists of multiple clumps of memory. From a NUMA perspective
> >> >   accesses to all clumps on the node have the same latency. Except for zone issues,
> >> >   the clumps are treated as equivalent for allocation/performance purposes.
> >> > 
> >> > - each node has a single contiguous mem_map array. The array contains page struct
> >> >   entries for every page on the node. There are no "holes" in the mem_map array.
> >> >   The node data area (see below) has pointers to the start of the mem_map entries
> >> >   for each clump on the node.
> >> 
> >> The mem_map array is the same on each node, copied from the boot_node
> >> to all other nodes. It contains page_struct entries for ALL pages on
> >> ALL nodes (if I interpret discontig_paging_init() correctly). The
> >> first two sentences need to be reformulated.
> 
> Arrrghh! Why on earth would you want to do that? How are you going to 
> atomically update things? Replicating things that are heavily written to is
> a bad idea.

We dont do that!!!


>  
> > 	- each node has a single contiguous page_struct array. This array contains page struct
> > 	  entries for every page that is actually present on the node. There are no 
> > 	  "holes" in the page_struct array for non-existent memory. Note that
> > 	  adjacent entries in the array are NOT necessarily for contiguous physical
> > 	  pages if there are multiple non-contiguous clumps on the node.
> 
> This sounds somewhat saner. I haven't read your code again recently (my head
> exploded last time I tried), but most people just use the lmem_map array per node
> to just have that node's struct pages.


That is what we do. 


> 
> M.
> 
> PS. If you wanted to change all the disgusting defns of PLAT_XXXXX to something
> readable, that would make a lot of people happy ;-)

No problem. What do you suggest.


> 
> 
> 
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-- 
Thanks

Jack Steiner    (651-683-5302)   (vnet 233-5302)      steiner@sgi.com