linux-kernel - [PATCH 2/6] mm: numa: Take THP into account when migrating pages for NUMA balancing

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Message-Id: <1358874762-19717-3-git-send-email-mgorman@suse.de>
Date:	Tue, 22 Jan 2013 17:12:38 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Simon Jeons <simon.jeons@...il.com>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Hugh Dickins <hughd@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/6] mm: numa: Take THP into account when migrating pages for NUMA balancing

Wanpeng Li pointed out that numamigrate_isolate_page() assumes that only one
base page is being migrated when in fact it can also be checking THP. The
consequences are that a migration will be attempted when a target node
is nearly full and fail later. It's unlikely to be user-visible but it
should be fixed. While we are there, migrate_balanced_pgdat() should treat
nr_migrate_pages as an unsigned long as it is treated as a watermark.

Suggested-by: Wanpeng Li <liwanp@...ux.vnet.ibm.com>
Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 mm/migrate.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index c387786..73e432d 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1459,7 +1459,7 @@ int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
  * pages. Currently it only checks the watermarks which crude
  */
 static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
-				   int nr_migrate_pages)
+				   unsigned long nr_migrate_pages)
 {
 	int z;
 	for (z = pgdat->nr_zones - 1; z >= 0; z--) {
@@ -1557,8 +1557,10 @@ int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
 {
 	int ret = 0;
 
+	VM_BUG_ON(compound_order(page) && !PageTransHuge(page));
+
 	/* Avoid migrating to a node that is nearly full */
-	if (migrate_balanced_pgdat(pgdat, 1)) {
+	if (migrate_balanced_pgdat(pgdat, 1UL << compound_order(page))) {
 		int page_lru;
 
 		if (isolate_lru_page(page)) {
-- 
1.7.9.2

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