Re: [PATCH 2/6] mm: mlocking in try_to_unmap_one

Hugh Dickins
2009-11-18T16:33:01Z

On Tue, 17 Nov 2009, KOSAKI Motohiro wrote:
>
> From 7332f765dbaa1fbfe48cf8d53b20048f7f8105e0 Mon Sep 17 00:00:00 2001
> From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Date: Tue, 17 Nov 2009 10:46:51 +0900
> Subject: comment adding to mlocking in try_to_unmap_one
>
> Current code doesn't tell us why we don't bother to nonlinear kindly.
> This patch added small adding explanation.
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>

(if the "MLOCK_PAGES && " is removed from this one too)

> ---
> mm/rmap.c | 6 +++++-
> 1 files changed, 5 insertions(+), 1 deletions(-)
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 81a168c..c631407 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1061,7 +1061,11 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
> if (list_empty(&mapping->i_mmap_nonlinear))
> goto out;
>
> - /* We don't bother to try to find the munlocked page in nonlinears */
> + /*
> + * We don't bother to try to find the munlocked page in nonlinears.
> + * It's costly. Instead, later, page reclaim logic may call
> + * try_to_unmap(TTU_MUNLOCK) and recover PG_mlocked lazily.
> + */
> if (MLOCK_PAGES && TTU_ACTION(flags) == TTU_MUNLOCK)
> goto out;
>
> --
> 1.6.2.5