linux-kernel - [PATCH] mem-hotplug: use GFP_HIGHUSER_MOVABLE and alloc from next node in alloc_migrate

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Date:	Thu, 14 Jul 2016 10:25:31 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	David Rientjes <rientjes@...gle.com>
CC:	Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] mem-hotplug: use GFP_HIGHUSER_MOVABLE and alloc from next
 node in alloc_migrate_target()

alloc_migrate_target() is called from migrate_pages(), and the page
is always from user space, so we can add __GFP_HIGHMEM directly.

Second, when we offline a node, the new page should alloced from other
nodes instead of the current node, because re-migrate is a waste of
time.

Signed-off-by: Xishi Qiu <qiuxishi@...wei.com>
---
 mm/page_isolation.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 612122b..83848dc 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -282,20 +282,16 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
 struct page *alloc_migrate_target(struct page *page, unsigned long private,
 				  int **resultp)
 {
-	gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
-
 	/*
-	 * TODO: allocate a destination hugepage from a nearest neighbor node,
+	 * TODO: allocate a destination page from a nearest neighbor node,
 	 * accordance with memory policy of the user process if possible. For
 	 * now as a simple work-around, we use the next node for destination.
 	 */
+	int nid = next_node_in(page_to_nid(page), node_online_map);
+
 	if (PageHuge(page))
 		return alloc_huge_page_node(page_hstate(compound_head(page)),
-					    next_node_in(page_to_nid(page),
-							 node_online_map));
-
-	if (PageHighMem(page))
-		gfp_mask |= __GFP_HIGHMEM;
-
-	return alloc_page(gfp_mask);
+						 nid);
+	else
+		return __alloc_pages_node(nid, GFP_HIGHUSER_MOVABLE, 0);
 }
-- 
1.8.3.1