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SubjectRe: [PATCH 5/6] mm, memory_hotplug: do not associate hotadded memory to zones until online
On Thu 30-03-17 13:54:53, Michal Hocko wrote:
[...]
> +static struct zone * __meminit move_pfn_range(int online_type, int nid,
> + unsigned long start_pfn, unsigned long nr_pages)
> +{
> + struct pglist_data *pgdat = NODE_DATA(nid);
> + struct zone *zone = &pgdat->node_zones[ZONE_NORMAL];
> +
> + if (online_type == MMOP_ONLINE_KEEP) {
> + /*
> + * MMOP_ONLINE_KEEP inherits the current zone which is
> + * ZONE_NORMAL by default but we might be within ZONE_MOVABLE
> + * already.
> + */
> + if (allow_online_pfn_range(nid, start_pfn, nr_pages, MMOP_ONLINE_MOVABLE))
> + zone = &pgdat->node_zones[ZONE_MOVABLE];
> + } else if (online_type == MMOP_ONLINE_MOVABLE) {
> + zone = &pgdat->node_zones[ZONE_MOVABLE];
> }
>
> - *zone_shift = target - idx;
> - return true;
> + move_pfn_range_to_zone(zone, start_pfn, nr_pages);
> + return zone;
> }

I got the MMOP_ONLINE_KEEP wrong here. Relying on allow_online_pfn_range
is wrong because that would lead to MMOP_ONLINE_MOVABLE by when there is
no ZONE_NORMAL while I believe we should online_kernel in that case.
Well the semantic of MMOP_ONLINE_KEEP is rathe fuzzy to me but I guess
it make some sense to online movable only when explicitly state or
_within_ and existing ZONE_MOVABLE. The following will fix this. I will
fold it into this patch.
---
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 7c4fef1aba84..0f8816fd0b52 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -531,6 +531,20 @@ static inline bool zone_is_empty(struct zone *zone)
}

/*
+ * Return true if [start_pfn, start_pfn + nr_pages) range has a non-mpty
+ * intersection with the given zone
+ */
+static inline bool zone_intersects(struct zone *zone,
+ unsigned long start_pfn, unsigned long nr_pages)
+{
+ if (zone->zone_start_pfn <= start_pfn && start_pfn < zone_end_pfn(zone))
+ return true;
+ if (start_pfn + nr_pages > start_pfn && !zone_is_empty(zone))
+ return true;
+ return false;
+}
+
+/*
* The "priority" of VM scanning is how much of the queues we will scan in one
* go. A value of 12 for DEF_PRIORITY implies that we will scan 1/4096th of the
* queues ("queue_length >> 12") during an aging round.
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 4f80abdc2047..2ff988f42377 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -934,13 +934,14 @@ static struct zone * __meminit move_pfn_range(int online_type, int nid,
struct zone *zone = &pgdat->node_zones[ZONE_NORMAL];

if (online_type == MMOP_ONLINE_KEEP) {
+ struct zone *movable_zone = &pgdat->node_zones[ZONE_MOVABLE];
/*
* MMOP_ONLINE_KEEP inherits the current zone which is
* ZONE_NORMAL by default but we might be within ZONE_MOVABLE
* already.
*/
- if (allow_online_pfn_range(nid, start_pfn, nr_pages, MMOP_ONLINE_MOVABLE))
- zone = &pgdat->node_zones[ZONE_MOVABLE];
+ if (zone_intersects(movable_zone, start_pfn, nr_pages))
+ zone = movable_zone;
} else if (online_type == MMOP_ONLINE_MOVABLE) {
zone = &pgdat->node_zones[ZONE_MOVABLE];
}
--
Michal Hocko
SUSE Labs
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