Re: [PATCH 2/3] staging: lowmemorykiller: count anon pages only when we have swap devices

From: David Rientjes
Date: Tue Jun 21 2016 - 16:22:13 EST


On Tue, 21 Jun 2016, Ganesh Mahendran wrote:

> lowmem_count() should only count anon pages when we have swap device.
>

Why?

> Signed-off-by: Ganesh Mahendran <opensource.ganesh@xxxxxxxxx>
> ---
> drivers/staging/android/lowmemorykiller.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
> index 6da9260..1d8de47 100644
> --- a/drivers/staging/android/lowmemorykiller.c
> +++ b/drivers/staging/android/lowmemorykiller.c
> @@ -73,10 +73,14 @@ static unsigned long lowmem_deathpending_timeout;
> static unsigned long lowmem_count(struct shrinker *s,
> struct shrink_control *sc)
> {
> - return global_page_state(NR_ACTIVE_ANON) +
> - global_page_state(NR_ACTIVE_FILE) +
> - global_page_state(NR_INACTIVE_ANON) +
> - global_page_state(NR_INACTIVE_FILE);
> + unsigned long freeable = global_page_state(NR_ACTIVE_FILE) +
> + global_page_state(NR_INACTIVE_FILE);
> +
> + if (get_nr_swap_pages() > 0)
> + freeable += global_page_state(NR_ACTIVE_ANON) +
> + global_page_state(NR_INACTIVE_ANON);
> +
> + return freeable;
> }
>
> static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)

Shouldn't this be advertising the amount of memory that is freeable by
killing the process with the highest priority oom_score_adj? It's not
legitimate to say it can free all anon and file memory if nothing is oom
killable, so this function is wrong both originally and with your patched
version.