Re: [PATCH] populated_map: fix !NUMA case, remove comment

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

On 13.06.2007 [15:50:41 -0700], Christoph Lameter wrote:
> On Wed, 13 Jun 2007, Nishanth Aravamudan wrote:
> 
> > I think your code above makes sense -- I'd still leave in the earlier
> > check, though.
> > 
> > So it probably should be:
> > 
> > 	pgdat = NODE_DATA(nid);
> > 	zonelist = pgdat->node_zonelists + gfp_zone(gfp_mask);
> > 
> > 	if (unlikely((gfp_mask & __GFP_THISNODE) &&
> > 		(!node_memory(nid) ||
> > 		 zonelist->zones[0]->zone_pgdat != pgdat)))
> > 		 return NULL;
> > 
> > That way, if the node has no memory whatsoever, we don't bother checking
> > the pgdat of the relevant zone?
> 
> Checking the pgdat is already done in __alloc_pages. No need to repeat
> it here.

Except that check is broken in the same way it is for memoryless nodes,
right?

from get_page_from_freelist():

                if (unlikely(NUMA_BUILD && (gfp_mask & __GFP_THISNODE) &&
                        zone->zone_pgdat != zonelist->zones[0]->zone_pgdat))

Which asks if for this zone, is the first node the same as each node we look at
for THISNODE requests. But if the first node for the zone is a
*different* node, we still satisfy the request, but go off-node?

Just trying to see if that maybe is the problem here?

Thanks,
Nish

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

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