kernel(三) mm

The important point to understand is that the page structure is associated with physical pages,not virtual pages.

        If a page is not free, the kernel needs to know who owns the page. Possible owners include user-space 

processes, dynamically allocated kernel data, static kernel code, the page cache, and so on.

 

Zones 

          the kernel divides pages into different zones.

 

         ZONE_DMA 

         ZONE_DMA32

         ZONE_NORMAL

         ZONE_HIGHMEM

         Note that the zones do not have any physical relevance but are simply logical 

groupings used by the kernel to keep track of pages.