Re: VM

On 6/14/07, cadastrosonline cadastrosonline
<cadastrosonline@xxxxxxxxxxxx> wrote:
"FreeBSD's memory allocation code implements page coloring optimizations, which means
that the memory allocation code will attempt to locate free pages that are contiguous
from the point of view of the cache. For example, if page 16 of physical memory is
assigned to page 0 of a process's virtual memory and the cache can hold 4 pages, the page
coloring code will not assign page 20 of physical memory to page 1 of a process's virtual
memory."

From fbsd books, I don't understand why it links page 16 of physical memory to page 0 then talks about page 20 of physcal memory to page 1, ok it will say it will sign to page 21 because of the page coloring, but thats not what i didnt get.

If the cache holds 4 pages, why wouldn't the physical page 20 sign to page 4 or 8 instead? Why 1? lol :> i see its signing the VM as 0,1,2,3,4 and the physical as 4,8,16,20...could anyone explain that?



I think, if virtual memory page 0 maps on physical memory page 16,
then virtual memory page 1 would map to physical memory page 17 and
that's the main idea. Instead, if you map vm page 1 to phys page 20
this will require cache invalidation on access.



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