Re: [PATCH] mm/madvise: add MADV_WILLNEED to process_madvise()

From: David Hildenbrand
Date: Wed Aug 04 2021 - 15:09:11 EST

On 04.08.21 10:20, zhangkui wrote:
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
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@xxxxxxxx>
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) {
return true;
return false;

I guess this should be fine. In contrast to other (e.g., destructive) madvise calls, an application could merely notice the difference that for example, in the pagemap something is suddenly no longer swapped, even thought the page wasn't touched by the process. But that can also happen e.g., during swapoff.

So I think this is fine, but let's hear if there are concerns.


David / dhildenb