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Subject[RFC PATCH v3 31/35] mm: Add a way to request pages of a particular region from the region allocator
Date
When moving freepages from one migratetype to another (using move_freepages()
or equivalent), we might encounter situations in which we would like to move
pages that are in the region allocator. In such cases, we need a way to
request pages of a particular region from the region allocator.

We already have the code to perform the heavy-lifting of actually moving the
pages of a region from the region allocator to a requested freelist or
migratetype. So just reorganize that code in such a way that we can also
pin-point a region and specify that we want the region allocator to allocate
pages from that particular region.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

mm/page_alloc.c | 40 ++++++++++++++++++++++++----------------
1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3f49ca8..fc530ff 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1002,24 +1002,18 @@ static void add_to_region_allocator(struct zone *z, struct free_list *free_list,
*next_region = region_id;
}

-/* Delete freepages from the region allocator and add them to buddy freelists */
-static int del_from_region_allocator(struct zone *zone, unsigned int order,
- int migratetype)
+static void __del_from_region_allocator(struct zone *zone, unsigned int order,
+ int migratetype, int region_id)
{
struct region_allocator *reg_alloc;
struct free_area_region *reg_area;
struct list_head *ralloc_list;
struct free_list *free_list;
unsigned long nr_pages;
- int next_region;
+ struct page *page;

reg_alloc = &zone->region_allocator;
-
- next_region = reg_alloc->next_region;
- if (next_region < 0)
- return -ENOMEM;
-
- reg_area = &reg_alloc->region[next_region].region_area[order];
+ reg_area = &reg_alloc->region[region_id].region_area[order];
ralloc_list = &reg_area->list;

list_for_each_entry(page, ralloc_list, lru)
@@ -1028,20 +1022,34 @@ static int del_from_region_allocator(struct zone *zone, unsigned int order,
free_list = &zone->free_area[order].free_list[migratetype];

nr_pages = add_to_freelist_bulk(ralloc_list, free_list, order,
- next_region);
+ region_id);

reg_area->nr_free -= nr_pages;
WARN_ON(reg_area->nr_free != 0);

/* Pick a new next_region */
- clear_bit(next_region, reg_alloc->ralloc_mask);
- next_region = find_first_bit(reg_alloc->ralloc_mask,
+ clear_bit(region_id, reg_alloc->ralloc_mask);
+ region_id = find_first_bit(reg_alloc->ralloc_mask,
MAX_NR_ZONE_REGIONS);

- if (next_region >= MAX_NR_ZONE_REGIONS)
- next_region = -1; /* No free regions available */
+ if (region_id >= MAX_NR_ZONE_REGIONS)
+ region_id = -1; /* No free regions available */
+
+ reg_alloc->next_region = region_id;
+}
+
+/* Delete freepages from the region allocator and add them to buddy freelists */
+static int del_from_region_allocator(struct zone *zone, unsigned int order,
+ int migratetype)
+{
+ int next_region;
+
+ next_region = zone->region_allocator.next_region;
+
+ if (next_region < 0)
+ return -ENOMEM;

- reg_alloc->next_region = next_region;
+ __del_from_region_allocator(zone, order, migratetype, next_region);

return 0;
}


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