linux-kernel - [RFC 6/6] mm: enable MADV

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Message-ID: <50b078171991f3ffdbdc34b6e0d7b3a146b7c859.1485748619.git.shli@fb.com>
Date:   Sun, 29 Jan 2017 21:51:23 -0800
From:   Shaohua Li <shli@...com>
To:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
CC:     <Kernel-team@...com>, <mhocko@...e.com>, <minchan@...nel.org>,
        <hughd@...gle.com>, <hannes@...xchg.org>, <riel@...hat.com>,
        <mgorman@...hsingularity.net>
Subject: [RFC 6/6] mm: enable MADV_FREE for swapless system

Now MADV_FREE pages can be easily reclaimed even for swapless system. We
can safely enable MADV_FREE for all systems.

Cc: Michal Hocko <mhocko@...e.com>
Cc: Minchan Kim <minchan@...nel.org>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Mel Gorman <mgorman@...hsingularity.net>
Signed-off-by: Shaohua Li <shli@...com>
---
 mm/madvise.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 78b4b02..047cfd4 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -579,13 +579,7 @@ madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 	case MADV_WILLNEED:
 		return madvise_willneed(vma, prev, start, end);
 	case MADV_FREE:
-		/*
-		 * XXX: In this implementation, MADV_FREE works like
-		 * MADV_DONTNEED on swapless system or full swap.
-		 */
-		if (get_nr_swap_pages() > 0)
-			return madvise_free(vma, prev, start, end);
-		/* passthrough */
+		return madvise_free(vma, prev, start, end);
 	case MADV_DONTNEED:
 		return madvise_dontneed(vma, prev, start, end);
 	default:
-- 
2.9.3