Re: ppc: RECLAIM_DISTANCE 10?

Michal Hocko
2014-02-19T08:33:41Z

On Tue 18-02-14 17:43:38, David Rientjes wrote:
> 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.

Agreed! Actually the code I am currently interested in is based on 3.0
kernel where zone_reclaim_mode is set in build_zonelists which relies on
find_next_best_node which iterates only N_HIGH_MEMORY nodes which should
have non 0 present pages.
[...]
--
Michal Hocko
SUSE Labs