Re: ppc: RECLAIM_DISTANCE 10?

Michal Hocko
2014-02-20T09:55:40Z

On Wed 19-02-14 08:33:45, Nishanth Aravamudan wrote:
> On 19.02.2014 [08:24:38 -0800], Nishanth Aravamudan wrote:
> > On 18.02.2014 [17:43:38 -0800], 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
> >
> > Gah, you're right.
> >
> > > 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.
> >
> > Yep, I found that afterwards, which simplifies the logic. I'll add this
> > to my series :)
>
> In looking at the code, I am wondering about the following:
>
> init_zone_allows_reclaim() is called for each nid from
> free_area_init_node(). Which means that calculate_node_totalpages for
> other "later" nids and check_for_memory() [which sets up the N_MEMORY
> nodemask] hasn't been called yet.
>
> So, would it make sense to pull up the
> /* Any memory on that node */
> if (pgdat->node_present_pages)
> node_set_state(nid, N_MEMORY);
> check_for_memory(pgdat, nid);
> into free_area_init_node()?

Dunno, but it shouldn't be needed because nodes are set N_MEMORY earlier
in early_calculate_totalpages as mentioned in other email.

--
Michal Hocko
SUSE Labs