[RFC][PATCH 1/2] mm: use MIGRATE_HIGHATOMIC as late as possible

[Xishi Qiu]

MIGRATE_HIGHATOMIC page blocks are reserved for an atomic
high-order allocation, so use it as late as possible.

Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
---
 mm/page_alloc.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 40d79a6..2331840 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2714,14 +2714,12 @@ struct page *rmqueue(struct zone *preferred_zone,
 	spin_lock_irqsave(&zone->lock, flags);
 
 	do {
-		page = NULL;
-		if (alloc_flags & ALLOC_HARDER) {
+		page = __rmqueue(zone, order, migratetype);
+		if (!page && 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);
 	if (!page)
-- 
1.8.3.1