[PATCH 08/10] mm, page_alloc: Remove MIGRATE_RESERVE
From: Mel Gorman
Date: Wed Aug 12 2015 - 06:47:17 EST
MIGRATE_RESERVE preserves an old property of the buddy allocator that existed
prior to fragmentation avoidance -- min_free_kbytes worth of pages tended to
remain contiguous until the only alternative was to fail the allocation. At the
time it was discovered that high-order atomic allocations relied on this
property so MIGRATE_RESERVE was introduced. A later patch will introduce
an alternative MIGRATE_HIGHATOMIC so this patch deletes MIGRATE_RESERVE
and supporting code so it'll be easier to review. Note that this patch
in isolation may look like a false regression if someone was bisecting
high-order atomic allocation failures.
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
---
include/linux/mmzone.h | 10 +---
mm/huge_memory.c | 2 +-
mm/page_alloc.c | 148 +++----------------------------------------------
mm/vmstat.c | 1 -
4 files changed, 11 insertions(+), 150 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 79a0d033a2f3..874755ca0abc 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -39,8 +39,6 @@ enum {
MIGRATE_UNMOVABLE,
MIGRATE_MOVABLE,
MIGRATE_RECLAIMABLE,
- MIGRATE_PCPTYPES, /* the number of types on the pcp lists */
- MIGRATE_RESERVE = MIGRATE_PCPTYPES,
#ifdef CONFIG_CMA
/*
* MIGRATE_CMA migration type is designed to mimic the way
@@ -63,6 +61,8 @@ enum {
MIGRATE_TYPES
};
+#define MIGRATE_PCPTYPES (MIGRATE_RECLAIMABLE+1)
+
#ifdef CONFIG_CMA
# define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA)
#else
@@ -425,12 +425,6 @@ struct zone {
const char *name;
- /*
- * Number of MIGRATE_RESERVE page block. To maintain for just
- * optimization. Protected by zone->lock.
- */
- int nr_migrate_reserve_block;
-
#ifdef CONFIG_MEMORY_ISOLATION
/*
* Number of isolated pageblock. It is used to solve incorrect
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f563473b5e99..ccf998194ae1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -113,7 +113,7 @@ static int set_recommended_min_free_kbytes(void)
for_each_populated_zone(zone)
nr_zones++;
- /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
+ /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
recommended_min = pageblock_nr_pages * nr_zones * 2;
/*
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 17064a3f4909..4708dadeaadf 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -793,7 +793,6 @@ static void free_pcppages_bulk(struct zone *zone, int count,
if (unlikely(has_isolate_pageblock(zone)))
mt = get_pageblock_migratetype(page);
- /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */
__free_one_page(page, page_to_pfn(page), zone, 0, mt);
trace_mm_page_pcpu_drain(page, 0, mt);
} while (--to_free && --batch_free && !list_empty(list));
@@ -1375,15 +1374,14 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
* the free lists for the desirable migrate type are depleted
*/
static int fallbacks[MIGRATE_TYPES][4] = {
- [MIGRATE_UNMOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE, MIGRATE_RESERVE },
- [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE, MIGRATE_MOVABLE, MIGRATE_RESERVE },
- [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_RESERVE },
+ [MIGRATE_UNMOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE, MIGRATE_TYPES },
+ [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE, MIGRATE_MOVABLE, MIGRATE_TYPES },
+ [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_TYPES },
#ifdef CONFIG_CMA
- [MIGRATE_CMA] = { MIGRATE_RESERVE }, /* Never used */
+ [MIGRATE_CMA] = { MIGRATE_TYPES }, /* Never used */
#endif
- [MIGRATE_RESERVE] = { MIGRATE_RESERVE }, /* Never used */
#ifdef CONFIG_MEMORY_ISOLATION
- [MIGRATE_ISOLATE] = { MIGRATE_RESERVE }, /* Never used */
+ [MIGRATE_ISOLATE] = { MIGRATE_TYPES }, /* Never used */
#endif
};
@@ -1557,7 +1555,7 @@ int find_suitable_fallback(struct free_area *area, unsigned int order,
*can_steal = false;
for (i = 0;; i++) {
fallback_mt = fallbacks[migratetype][i];
- if (fallback_mt == MIGRATE_RESERVE)
+ if (fallback_mt == MIGRATE_TYPES)
break;
if (list_empty(&area->free_list[fallback_mt]))
@@ -1636,25 +1634,13 @@ static struct page *__rmqueue(struct zone *zone, unsigned int order,
{
struct page *page;
-retry_reserve:
page = __rmqueue_smallest(zone, order, migratetype);
-
- if (unlikely(!page) && migratetype != MIGRATE_RESERVE) {
+ if (unlikely(!page)) {
if (migratetype == MIGRATE_MOVABLE)
page = __rmqueue_cma_fallback(zone, order);
if (!page)
page = __rmqueue_fallback(zone, order, migratetype);
-
- /*
- * Use MIGRATE_RESERVE rather than fail an allocation. goto
- * is used because __rmqueue_smallest is an inline function
- * and we want just one call site
- */
- if (!page) {
- migratetype = MIGRATE_RESERVE;
- goto retry_reserve;
- }
}
trace_mm_page_alloc_zone_locked(page, order, migratetype);
@@ -3443,7 +3429,6 @@ static void show_migration_types(unsigned char type)
[MIGRATE_UNMOVABLE] = 'U',
[MIGRATE_RECLAIMABLE] = 'E',
[MIGRATE_MOVABLE] = 'M',
- [MIGRATE_RESERVE] = 'R',
#ifdef CONFIG_CMA
[MIGRATE_CMA] = 'C',
#endif
@@ -4254,120 +4239,6 @@ static inline unsigned long wait_table_bits(unsigned long size)
}
/*
- * Check if a pageblock contains reserved pages
- */
-static int pageblock_is_reserved(unsigned long start_pfn, unsigned long end_pfn)
-{
- unsigned long pfn;
-
- for (pfn = start_pfn; pfn < end_pfn; pfn++) {
- if (!pfn_valid_within(pfn) || PageReserved(pfn_to_page(pfn)))
- return 1;
- }
- return 0;
-}
-
-/*
- * Mark a number of pageblocks as MIGRATE_RESERVE. The number
- * of blocks reserved is based on min_wmark_pages(zone). The memory within
- * the reserve will tend to store contiguous free pages. Setting min_free_kbytes
- * higher will lead to a bigger reserve which will get freed as contiguous
- * blocks as reclaim kicks in
- */
-static void setup_zone_migrate_reserve(struct zone *zone)
-{
- unsigned long start_pfn, pfn, end_pfn, block_end_pfn;
- struct page *page;
- unsigned long block_migratetype;
- int reserve;
- int old_reserve;
-
- /*
- * Get the start pfn, end pfn and the number of blocks to reserve
- * We have to be careful to be aligned to pageblock_nr_pages to
- * make sure that we always check pfn_valid for the first page in
- * the block.
- */
- start_pfn = zone->zone_start_pfn;
- end_pfn = zone_end_pfn(zone);
- start_pfn = roundup(start_pfn, pageblock_nr_pages);
- reserve = roundup(min_wmark_pages(zone), pageblock_nr_pages) >>
- pageblock_order;
-
- /*
- * Reserve blocks are generally in place to help high-order atomic
- * allocations that are short-lived. A min_free_kbytes value that
- * would result in more than 2 reserve blocks for atomic allocations
- * is assumed to be in place to help anti-fragmentation for the
- * future allocation of hugepages at runtime.
- */
- reserve = min(2, reserve);
- old_reserve = zone->nr_migrate_reserve_block;
-
- /* When memory hot-add, we almost always need to do nothing */
- if (reserve == old_reserve)
- return;
- zone->nr_migrate_reserve_block = reserve;
-
- for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
- if (!early_page_nid_uninitialised(pfn, zone_to_nid(zone)))
- return;
-
- if (!pfn_valid(pfn))
- continue;
- page = pfn_to_page(pfn);
-
- /* Watch out for overlapping nodes */
- if (page_to_nid(page) != zone_to_nid(zone))
- continue;
-
- block_migratetype = get_pageblock_migratetype(page);
-
- /* Only test what is necessary when the reserves are not met */
- if (reserve > 0) {
- /*
- * Blocks with reserved pages will never free, skip
- * them.
- */
- block_end_pfn = min(pfn + pageblock_nr_pages, end_pfn);
- if (pageblock_is_reserved(pfn, block_end_pfn))
- continue;
-
- /* If this block is reserved, account for it */
- if (block_migratetype == MIGRATE_RESERVE) {
- reserve--;
- continue;
- }
-
- /* Suitable for reserving if this block is movable */
- if (block_migratetype == MIGRATE_MOVABLE) {
- set_pageblock_migratetype(page,
- MIGRATE_RESERVE);
- move_freepages_block(zone, page,
- MIGRATE_RESERVE);
- reserve--;
- continue;
- }
- } else if (!old_reserve) {
- /*
- * At boot time we don't need to scan the whole zone
- * for turning off MIGRATE_RESERVE.
- */
- break;
- }
-
- /*
- * If the reserve is met and this is a previous reserved block,
- * take it back
- */
- if (block_migratetype == MIGRATE_RESERVE) {
- set_pageblock_migratetype(page, MIGRATE_MOVABLE);
- move_freepages_block(zone, page, MIGRATE_MOVABLE);
- }
- }
-}
-
-/*
* Initially all pages are reserved - free ones are freed
* up by free_all_bootmem() once the early boot process is
* done. Non-atomic initialization, single-pass.
@@ -4406,9 +4277,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
* movable at startup. This will force kernel allocations
* to reserve their blocks rather than leaking throughout
* the address space during boot when many long-lived
- * kernel allocations are made. Later some blocks near
- * the start are marked MIGRATE_RESERVE by
- * setup_zone_migrate_reserve()
+ * kernel allocations are made.
*
* bitmap is created for zone's valid pfn range. but memmap
* can be created for invalid pages (for alignment)
@@ -5958,7 +5827,6 @@ static void __setup_per_zone_wmarks(void)
high_wmark_pages(zone) - low_wmark_pages(zone) -
atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH]));
- setup_zone_migrate_reserve(zone);
spin_unlock_irqrestore(&zone->lock, flags);
}
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 4f5cd974e11a..49963aa2dff3 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -901,7 +901,6 @@ static char * const migratetype_names[MIGRATE_TYPES] = {
"Unmovable",
"Reclaimable",
"Movable",
- "Reserve",
#ifdef CONFIG_CMA
"CMA",
#endif
--
2.4.6
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/