Re: [RFC] Initial alpha-0 for new page allocator API

Christoph Lameter
2006-09-22T17:36:03Z

The problems to be solved are:

1. Have a means to allocate from a range of memory that is defined by the
device driver and *not* by the architecture. Devices currently cannot rely
on GFP_DMA because the range vary according to the architecture.

2. I wish we there would be some point in the future where we could get
rid of GFP_DMAxx... As Andi notes most hardware these days is sane so
there is less need to create VM overhead by managing additional zones.

3. There are issues with memory policies coming from the process
environment that may redirect allocations. We also have additional calls
with xx_node like alloc_pages and alloc_pages_node. A new API could
fix these and allow a complete specification of how the allocation should
proceeds without strange side effect from the process (which makes
GFP_THISNODE necessary).

One easy alternate way to support allocating from a range of memory
without reworking the API would be to simply add a new page allocator
call:

struct page *alloc_pages_range(int order, gfp_t gfp_flags, unsigned long
low, unsigned long high [ , node ? ]);

This would scan through the freelists for available memory in that range
and if not found simply do page reclaim until such memory becomes
available. We could get more sophisticated than that but this would allow
allocating memory from the ranges needed by broken devices and it would
penalize the device for the problem it has and would not impact the rest
of the system.