On Wed, 19 Feb 2014, Nishanth Aravamudan wrote:
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 3e953f07edb0..4a44bdc7a8cf 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1855,7 +1855,7 @@ static void __paginginit init_zone_allows_reclaim(int nid)
> > {
> > int i;
> >
> > - for_each_online_node(i)
> > + for_each_node_state(i, N_HIGH_MEMORY)
> > if (node_distance(nid, i) <= RECLAIM_DISTANCE)
> > node_set(i, NODE_DATA(nid)->reclaim_nodes);
> > else
> > @@ -4901,7 +4901,8 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
> >
> > pgdat->node_id = nid;
> > pgdat->node_start_pfn = node_start_pfn;
> > - init_zone_allows_reclaim(nid);
> > + if (node_state(nid, N_HIGH_MEMORY))
> > + init_zone_allows_reclaim(nid);
>
> I'm still new to this code, but isn't this saying that if a node has no
> memory, then it shouldn't reclaim from any node? But, for a memoryless
> node to ensure progress later if reclaim is necessary, it *must* reclaim
> from other nodes? So wouldn't we want to set reclaim_nodes() in that
> case to node_states[N_MEMORY]?
>
The only time when pgdat->reclaim_nodes or zone_reclaim_mode matters is
when iterating through a zonelist for page allocation and a memoryless
node should never appear in a zonelist for page allocation, so this is
just preventing setting zone_reclaim_mode unnecessarily because the only
nodes with > RECLAIM_DISTANCE to another node are memoryless. So this
patch is fine as long as it gets s/N_HIGH_MEMORY/N_MEMORY/.
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
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