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

[Nishanth Aravamudan <nacc@us.ibm.com>]

On 14.06.2007 [00:07:28 -0700], Christoph Lameter wrote:
> On Wed, 13 Jun 2007, Lee Schermerhorn wrote:
> 
> > --- Linux.orig/include/linux/gfp.h	2007-06-13 16:36:02.000000000 -0400
> > +++ Linux/include/linux/gfp.h	2007-06-13 16:38:41.000000000 -0400
> > @@ -168,6 +168,9 @@ FASTCALL(__alloc_pages(gfp_t, unsigned i
> >  static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
> >  						unsigned int order)
> >  {
> > +	pg_data_t *pgdat;
> > +	struct zonelist *zonelist;
> > +
> >  	if (unlikely(order >= MAX_ORDER))
> >  		return NULL;
> >  
> > @@ -179,11 +182,13 @@ static inline struct page *alloc_pages_n
> >  	 * Check for the special case that GFP_THISNODE is used on a
> >  	 * memoryless node
> >  	 */
> > -	if ((gfp_mask & __GFP_THISNODE) && !node_memory(nid))
> > +	pgdat = NODE_DATA(nid);
> > +	zonelist = pgdat->node_zonelists + gfp_zone(gfp_mask);
> > +	if ((gfp_mask & __GFP_THISNODE) &&
> > +		pgdat != zonelist->zones[0]->zone_pgdat)
> >  		return NULL;
> >  
> > -	return __alloc_pages(gfp_mask, order,
> > -		NODE_DATA(nid)->node_zonelists + gfp_zone(gfp_mask));
> > +	return __alloc_pages(gfp_mask, order, zonelist);
> >  }
> 
> Good idea but I think this does not address the case where the DMA
> zone of a node was moved to the end of the zonelist. In that case the
> first zone is not on the first pgdat but the node has memory. The
> memory of the node is listed elsewhere in the nodelist. I can probably
> modify __alloc_pages to make GFP_THISNODE to check all zones but we do
> not have the pgdat reference there. Sigh.
> 
> How about generating a special THISNODE zonelist in build_zonelist
> that only contains the zones of a single node. Then just use that one
> if GFP_THISNODE is set. Then we get rid of all the GFP_THISNODE crap
> that I added to __alloc_pages?

Makes sense to me.

Thanks,
NIsh

-- 
Nishanth Aravamudan <nacc@us.ibm.com>
IBM Linux Technology Center

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