On Mon 06-02-17 23:43:14, Wei Yang wrote: > The whole memory space is divided into several zones and nodes may have no > page in some zones. In this case, the __absent_pages_in_range() would > return 0, since the range it is searching for is an empty range. > > Also this happens more often to those nodes with higher memory range when > there are more nodes, which is a trend for future architectures.
I do not understand this part. Why would we see more zones with zero pfn range in higher memory ranges. > This patch checks the zone range after clamp and adjustment, return 0 if > the range is an empty range. I assume the whole point of this patch is to save __absent_pages_in_range which iterates over all memblock regions, right? Is there any reason why for_each_mem_pfn_range cannot be changed to honor the given start/end pfns instead? I can imagine that a small zone would see a similar pointless iterations... > Signed-off-by: Wei Yang <richard.weiy...@gmail.com> > --- > mm/page_alloc.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 6de9440e3ae2..51c60c0eadcb 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5521,6 +5521,11 @@ static unsigned long __meminit > zone_absent_pages_in_node(int nid, > adjust_zone_range_for_zone_movable(nid, zone_type, > node_start_pfn, node_end_pfn, > &zone_start_pfn, &zone_end_pfn); > + > + /* If this node has no page within this zone, return 0. */ > + if (zone_start_pfn == zone_end_pfn) > + return 0; > + > nr_absent = __absent_pages_in_range(nid, zone_start_pfn, zone_end_pfn); > > /* > -- > 2.11.0 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majord...@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"d...@kvack.org";> em...@kvack.org </a> -- Michal Hocko SUSE Labs
