Re: [PATCH 6/6] Use one zonelist that is filtered by nodemask

Christoph Lameter
2007-10-09T01:56:18Z

On Mon, 8 Oct 2007, Nishanth Aravamudan wrote:

> > struct page * fastcall
> > __alloc_pages(gfp_t gfp_mask, unsigned int order,
> > struct zonelist *zonelist)
> > {
> > + /*
> > + * Use a temporary nodemask for __GFP_THISNODE allocations. If the
> > + * cost of allocating on the stack or the stack usage becomes
> > + * noticable, allocate the nodemasks per node at boot or compile time
> > + */
> > + if (unlikely(gfp_mask & __GFP_THISNODE)) {
> > + nodemask_t nodemask;
> > +
> > + return __alloc_pages_internal(gfp_mask, order,
> > + zonelist, nodemask_thisnode(&nodemask));
> > + }
> > +
> > return __alloc_pages_internal(gfp_mask, order, zonelist, NULL);
> > }
>
> <snip>
>
> So alloc_pages_node() calls here and for THISNODE allocations, we go ask
> nodemask_thisnode() for a nodemask...

Hmmmm... nodemask_thisnode needs to be passed the zonelist.

> And nodemask_thisnode() always gives us a nodemask with only the node
> the current process is running on set, I think?

Right.

> That seems really wrong -- and would explain what Lee was seeing while
> using my patches for the hugetlb pool allocator to use THISNODE
> allocations. All the allocations would end up coming from whatever node
> the process happened to be running on. This obviously messes up hugetlb
> accounting, as I rely on THISNODE requests returning NULL if they go
> off-node.
>
> I'm not sure how this would be fixed, as __alloc_pages() no longer has
> the nid to set in the mask.
>
> Am I wrong in my analysis?

No you are right on target. The thisnode function must determine the node
from the first zone of the zonelist.