RE: [RFC] Variable Kernel Page size support

["Chen, Kenneth W" <kenneth.w.chen@intel.com>]

Christoph Lameter wrote on Thursday, October 12, 2006 5:33 PM
> If set then a lookup is performed using the region7_pgdir table.
> That table is segmented into 8 section for the varying page
> sizes supported.
> 
> 0 = _PAGE_SIZE_64K
> 1 = _PAGE_SIZE_256K
> 2 = _PAGE_SIZE_1M
> 3 = _PAGE_SIZE_4M
> 4 = _PAGE_SIZE_16M
> 5 = _PAGE_SIZE_64M
> 6 = _PAGE_SIZE_256M and _PAGE_SIZE_4K and _PAGE_SIZE_8K
> 7 = _PAGE_SIZE_1G and PAGE_SIZE_16k

Another thing cross my mind is that this is in region 7, and effectively
vhpt is disabled for those sections of virtual address.  I suppose the
larger page size will win back the loss from not using vhpt.  And this
trade off also depends on data access pattern.  Some of the small page
size will take  double hit on (1) being very small and (2) not having
vhpt to mitigate tlb miss latency.  You might want to just drop those
small sizes.