linux-kernel - [PATCH -mm -v3 04/12] mm, THP, swap: Don't allocate huge cluster for file backed swap device

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Message-Id: <20170724051840.2309-5-ying.huang@intel.com>
Date:   Mon, 24 Jul 2017 13:18:32 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Huang Ying <ying.huang@...el.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Minchan Kim <minchan@...nel.org>,
        Hugh Dickins <hughd@...gle.com>, Shaohua Li <shli@...nel.org>,
        Rik van Riel <riel@...hat.com>
Subject: [PATCH -mm -v3 04/12] mm, THP, swap: Don't allocate huge cluster for file backed swap device

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

It's hard to write a whole transparent huge page (THP) to a file
backed swap device during swapping out and the file backed swap device
isn't very popular.  So the huge cluster allocation for the file
backed swap device is disabled.

Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Minchan Kim <minchan@...nel.org>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Shaohua Li <shli@...nel.org>
Cc: Rik van Riel <riel@...hat.com>
---
 mm/swapfile.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index b110faf3c82a..21cbdecbc19a 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -948,9 +948,10 @@ int get_swap_pages(int n_goal, bool cluster, swp_entry_t swp_entries[])
 			spin_unlock(&si->lock);
 			goto nextsi;
 		}
-		if (cluster)
-			n_ret = swap_alloc_cluster(si, swp_entries);
-		else
+		if (cluster) {
+			if (!(si->flags & SWP_FILE))
+				n_ret = swap_alloc_cluster(si, swp_entries);
+		} else
 			n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
 						    n_goal, swp_entries);
 		spin_unlock(&si->lock);
-- 
2.13.2