Re: [1/3] Add __GFP_THISNODE to avoid fallback to other nodes and ignore cpuset/memory policy restrictions.

[Christoph Lameter <clameter@sgi.com>]

On Tue, 8 Aug 2006, Mel Gorman wrote:

> On Tue, 8 Aug 2006, Christoph Lameter wrote:
> 
> > Add a new gfp flag __GFP_THISNODE to avoid fallback to other nodes. This
> > flag
> > is essential if a kernel component requires memory to be located on a
> > certain node. It will be needed for alloc_pages_node() to force allocation
> > on the indicated node and for alloc_pages() to force allocation on the
> > current node.
> > 
> 
> GFP flags are getting a bit tight. Could this also be done by providing

Right they are gettin scarce.

> alloc_pages_zonelist(int nid, gfp_t gfp_mask, unsigned int order,  struct
> zonelist *));
> 
> alloc_pages_node() would be altered to call alloc_pages_zonelist() with the
> currect zonelist. To avoid fallbacks, callers would need a helper function
> that provided a zonelist with just zones in a single node.

We would need a whole selection of allocators for this purpose. Some 
candidates:

alloc_pages_current
alloc_pages_node
vmalloc
vmalloc_node
dma_alloc_coherent

etc


 > That would give the ability to avoid fallbacks at least. Avoiding policy
> temporarily is a bit harder but it is really needed?

Policy and cpusets can redirect allocations. That is one of the key 
problems.

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