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Subject[PATCH 1/3] mm, page_alloc: Split buffered_rmqueue
Date
buffered_rmqueue removes a page from a given zone and uses the per-cpu
list for order-0. This is fine but a hypothetical caller that wanted
multiple order-0 pages has to disable/reenable interrupts multiple
times. This patch structures buffere_rmqueue such that it's relatively
easy to build a bulk order-0 page allocator. There is no functional
change.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
---
mm/page_alloc.c | 126 ++++++++++++++++++++++++++++++++++----------------------
1 file changed, 77 insertions(+), 49 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2c6d5f64feca..d8798583eaf8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2610,68 +2610,96 @@ static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,
#endif
}

+/* Remote page from the per-cpu list, caller must protect the list */
+static struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
+ gfp_t gfp_flags, int migratetype, bool cold,
+ struct per_cpu_pages *pcp, struct list_head *list)
+{
+ struct page *page;
+
+ do {
+ if (list_empty(list)) {
+ pcp->count += rmqueue_bulk(zone, 0,
+ pcp->batch, list,
+ migratetype, cold);
+ if (unlikely(list_empty(list)))
+ return NULL;
+ }
+
+ if (cold)
+ page = list_last_entry(list, struct page, lru);
+ else
+ page = list_first_entry(list, struct page, lru);
+
+ list_del(&page->lru);
+ pcp->count--;
+ } while (check_new_pcp(page));
+
+ return page;
+}
+
+/* Lock and remove page from the per-cpu list */
+static struct page *rmqueue_pcplist(struct zone *preferred_zone,
+ struct zone *zone, unsigned int order,
+ gfp_t gfp_flags, int migratetype)
+{
+ struct per_cpu_pages *pcp;
+ struct list_head *list;
+ bool cold = ((gfp_flags & __GFP_COLD) != 0);
+ struct page *page;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ pcp = &this_cpu_ptr(zone->pageset)->pcp;
+ list = &pcp->lists[migratetype];
+ page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
+ cold, pcp, list);
+ if (page) {
+ __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
+ zone_statistics(preferred_zone, zone, gfp_flags);
+ }
+ local_irq_restore(flags);
+ return page;
+}
+
/*
* Allocate a page from the given zone. Use pcplists for order-0 allocations.
*/
static inline
-struct page *buffered_rmqueue(struct zone *preferred_zone,
+struct page *rmqueue(struct zone *preferred_zone,
struct zone *zone, unsigned int order,
gfp_t gfp_flags, unsigned int alloc_flags,
int migratetype)
{
unsigned long flags;
struct page *page;
- bool cold = ((gfp_flags & __GFP_COLD) != 0);
-
- if (likely(order == 0)) {
- struct per_cpu_pages *pcp;
- struct list_head *list;
-
- local_irq_save(flags);
- do {
- pcp = &this_cpu_ptr(zone->pageset)->pcp;
- list = &pcp->lists[migratetype];
- if (list_empty(list)) {
- pcp->count += rmqueue_bulk(zone, 0,
- pcp->batch, list,
- migratetype, cold);
- if (unlikely(list_empty(list)))
- goto failed;
- }
-
- if (cold)
- page = list_last_entry(list, struct page, lru);
- else
- page = list_first_entry(list, struct page, lru);

- list_del(&page->lru);
- pcp->count--;
+ if (likely(order == 0))
+ return rmqueue_pcplist(preferred_zone, zone, order,
+ gfp_flags, migratetype);

- } while (check_new_pcp(page));
- } else {
- /*
- * We most definitely don't want callers attempting to
- * allocate greater than order-1 page units with __GFP_NOFAIL.
- */
- WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
- spin_lock_irqsave(&zone->lock, flags);
+ /*
+ * We most definitely don't want callers attempting to
+ * allocate greater than order-1 page units with __GFP_NOFAIL.
+ */
+ WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
+ spin_lock_irqsave(&zone->lock, flags);

- do {
- page = NULL;
- if (alloc_flags & ALLOC_HARDER) {
- page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
- if (page)
- trace_mm_page_alloc_zone_locked(page, order, migratetype);
- }
- if (!page)
- page = __rmqueue(zone, order, migratetype);
- } while (page && check_new_pages(page, order));
- spin_unlock(&zone->lock);
+ do {
+ page = NULL;
+ if (alloc_flags & ALLOC_HARDER) {
+ page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
+ if (page)
+ trace_mm_page_alloc_zone_locked(page, order, migratetype);
+ }
if (!page)
- goto failed;
- __mod_zone_freepage_state(zone, -(1 << order),
- get_pcppage_migratetype(page));
- }
+ page = __rmqueue(zone, order, migratetype);
+ } while (page && check_new_pages(page, order));
+ spin_unlock(&zone->lock);
+ if (!page)
+ goto failed;
+ __mod_zone_freepage_state(zone, -(1 << order),
+ get_pcppage_migratetype(page));

__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
zone_statistics(preferred_zone, zone, gfp_flags);
@@ -2982,7 +3010,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
}

try_this_zone:
- page = buffered_rmqueue(ac->preferred_zoneref->zone, zone, order,
+ page = rmqueue(ac->preferred_zoneref->zone, zone, order,
gfp_mask, alloc_flags, ac->migratetype);
if (page) {
prep_new_page(page, order, gfp_mask, alloc_flags);
--
2.11.0
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