Re: [patch 2/3] Fix GFP_THISNODE behavior for memoryless nodes

Christoph Lameter
2007-06-14T14:24:55Z

On Thu, 14 Jun 2007, Lee Schermerhorn wrote:

> > That check is already done by __alloc_pages.
>
> You mean in get_page_from_freelist()? No, it only checks that the zone
> under consideration is on the same node as the zone at the start of the
> list. This can be off-node if the node is populated only at lower
> zones; and the zonelists are in zone-order.

See the later discussion. I did not see the use the nodes pgdat here that
you only have in alloc_pages_node().

> > Ummm... Slub would need to consult node_memory_map instead I guess.
>
> Probably should check the node_memory_map to avoid attempting
> allocations from completely memoryless nodes. However, it should still
> be able to handle nulls from alloc_pages_nodes() because of the
> scenarios discussed above.

It is able to handle NULLs during usual operations but not during bootstrap.

> Again, node_memory_map can't detect the "first zone in zonelist
> off-node" situation. That's the one that alloc_pages_node() must guard
> against. So, it can/should/must return NULL when attempting to
> allocate from a higher zone that is off-node.

I think GFP_THISNODE should not fail in that case.