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From: "Huang, Ying" <ying.huang@intel.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Huang Ying <ying.huang@intel.com>,
	Johannes Weiner <hannes@cmpxchg.org>
Subject: [PATCH -mm -v8 3/3] mm, THP, swap: Enable THP swap optimization only if has compound map
Date: Thu,  6 Apr 2017 13:35:15 +0800	[thread overview]
Message-ID: <20170406053515.4842-4-ying.huang@intel.com> (raw)
In-Reply-To: <20170406053515.4842-1-ying.huang@intel.com>

From: Huang Ying <ying.huang@intel.com>

If there is no compound map for a THP (Transparent Huge Page), it is
possible that the map count of some sub-pages of the THP is 0.  So it
is better to split the THP before swapping out. In this way, the
sub-pages not mapped will be freed, and we can avoid the unnecessary
swap out operations for these sub-pages.

Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
---
 mm/swap_state.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 612fb2418df6..528af29327c9 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -205,7 +205,9 @@ int add_to_swap(struct page *page, struct list_head *list)
 		/* cannot split, skip it */
 		if (!can_split_huge_page(page, NULL))
 			return 0;
-		huge = true;
+		/* fallback to split huge page firstly if no PMD map */
+		if (compound_mapcount(page))
+			huge = true;
 	}
 #endif
 
-- 
2.11.0

      parent reply	other threads:[~2017-04-06  5:36 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-06  5:35 [PATCH -mm -v8 0/3] THP swap: Delay splitting THP during swapping out Huang, Ying
2017-04-06  5:35 ` [PATCH -mm -v8 1/3] mm, THP, swap: Delay splitting THP during swap out Huang, Ying
2017-04-14 14:58   ` Johannes Weiner
2017-04-15  1:17     ` Huang, Ying
2017-04-17 18:24       ` Johannes Weiner
2017-04-18  0:33         ` Huang, Ying
2017-04-06  5:35 ` [PATCH -mm -v8 2/3] mm, THP, swap: Check whether THP can be split firstly Huang, Ying
2017-04-06  5:35 ` Huang, Ying [this message]

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