Re: ppc: RECLAIM_DISTANCE 10?

David Rientjes
2014-02-19T01:43:41Z

On Tue, 18 Feb 2014, Nishanth Aravamudan wrote:

> How about the following?
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 5de4337..1a0eced 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1854,7 +1854,8 @@ static void __paginginit init_zone_allows_reclaim(int nid)
> int i;
>
> for_each_online_node(i)
> - if (node_distance(nid, i) <= RECLAIM_DISTANCE)
> + if (node_distance(nid, i) <= RECLAIM_DISTANCE ||
> + !NODE_DATA(i)->node_present_pages)
> node_set(i, NODE_DATA(nid)->reclaim_nodes);
> else
> zone_reclaim_mode = 1;

[ I changed the above from NODE_DATA(nid) -> NODE_DATA(i) as you caught
so we're looking at the right code. ]

That can't be right, it would allow reclaiming from a memoryless node. I
think what you want is

for_each_online_node(i) {
if (!node_present_pages(i))
continue;
if (node_distance(nid, i) <= RECLAIM_DISTANCE) {
node_set(i, NODE_DATA(nid)->reclaim_nodes);
continue;
}
/* Always try to reclaim locally */
zone_reclaim_mode = 1;
}

but we really should be able to do for_each_node_state(i, N_MEMORY) here
and memoryless nodes should already be excluded from that mask.

> @@ -4901,13 +4902,13 @@ 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);
> #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
> get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
> #endif
> calculate_node_totalpages(pgdat, start_pfn, end_pfn,
> zones_size, zholes_size);
>
> + init_zone_allows_reclaim(nid);
> alloc_node_mem_map(pgdat);
> #ifdef CONFIG_FLAT_NODE_MEM_MAP
> printk(KERN_DEBUG "free_area_init_node: node %d, pgdat %08lx, node_mem_map %08lx\n",
>
> I think it's safe to move init_zone_allows_reclaim, because I don't
> think any allocates are occurring here that could cause us to reclaim
> anyways, right? Moving it allows us to safely reference
> node_present_pages.
>

Yeah, this is fine.