[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 <qiuxi...@huawei.com>
---
 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