Re: ppc: RECLAIM_DISTANCE 10?

Nishanth Aravamudan
2014-02-19T16:59:55Z

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()?

Thanks,
Nish