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From:   zhangkui <zhangkui@oppo.com>
To:     akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Cc:     zhangkui <zhangkui@oppo.com>
Subject: [PATCH] mm/madvise: add MADV_WILLNEED to process_madvise()
Date:   Wed,  4 Aug 2021 16:20:10 +0800
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There is a usecase in Android that an app process's memory is swapped out
by process_madvise() with MADV_PAGEOUT, such as the memory is swapped to
zram or a backing device. When the process is scheduled to running, like
switch to foreground, multiple page faults may cause the app dropped
frames.
To reduce the problem, SMS can read-ahead memory of the process immediately
when the app switches to forground.
Calling process_madvise() with MADV_WILLNEED can meet this need.

Signed-off-by: zhangkui <zhangkui@oppo.com>
---
 mm/madvise.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/madvise.c b/mm/madvise.c
index 6d3d348b17f4..b9681fb3fbb5 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1046,6 +1046,7 @@ process_madvise_behavior_valid(int behavior)
        switch (behavior) {
        case MADV_COLD:
        case MADV_PAGEOUT:
+       case MADV_WILLNEED:
                return true;
        default:
                return false;
--
2.25.1

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