mm, page_alloc: remove MIGRATE_RESERVE
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@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 1e88aae..b86cfa3 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -39,8 +39,6 @@
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 @@
MIGRATE_TYPES
};
+#define MIGRATE_PCPTYPES (MIGRATE_RECLAIMABLE+1)
+
#ifdef CONFIG_CMA
# define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA)
#else
@@ -429,12 +429,6 @@
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 9812d46..dabd247 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -116,7 +116,7 @@
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 8dc6e3c..5888126 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -817,7 +817,6 @@
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));
@@ -1417,15 +1416,14 @@
* 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
};
@@ -1598,7 +1596,7 @@
*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]))
@@ -1676,25 +1674,13 @@
{
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);
@@ -3492,7 +3478,6 @@
[MIGRATE_UNMOVABLE] = 'U',
[MIGRATE_RECLAIMABLE] = 'E',
[MIGRATE_MOVABLE] = 'M',
- [MIGRATE_RESERVE] = 'R',
#ifdef CONFIG_CMA
[MIGRATE_CMA] = 'C',
#endif
@@ -4303,120 +4288,6 @@
}
/*
- * 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.
@@ -4455,9 +4326,7 @@
* 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)
@@ -6018,7 +5887,6 @@
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 ffcb4f5..5b289dc 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -923,7 +923,6 @@
"Unmovable",
"Reclaimable",
"Movable",
- "Reserve",
#ifdef CONFIG_CMA
"CMA",
#endif