linux-kernel - Re: [PATCH] mmap: Fix and tidy up overcommit page arithmetic

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Date:	Mon, 11 Jul 2011 08:08:46 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Dmitry Fink <dmitry.fink@...m.com>
Cc:	Hugh Dickins <hughd@...gle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmap: Fix and tidy up overcommit page arithmetic

On Sun, Jul 10, 2011 at 5:55 AM, Dmitry Fink <dmitry.fink@...m.com> wrote:
> - shmem pages are not immediately available, but they are not
> potentially available either, even if we swap them out, they will
> just relocate from memory into swap, total amount of immediate and
> potentially available memory is not going to be affected, so we
> shouldn't count them as potentially free in the first place.
>
> - nr_free_pages() is not an expensive operation anymore, there is
> no need to split the decision making in two halves and repeat code.
>
> Signed-off-by: Dmitry Fink <dmitry.fink@...m.com>
> Reviewed-by: Minchan Kim <minchan.kim@...il.com>
> Acked-by: Hugh Dickins <hughd@...gle.com>
> ---
>  mm/mmap.c  |   33 ++++++++++++---------------------
>  mm/nommu.c |   33 ++++++++++++---------------------
>  2 files changed, 24 insertions(+), 42 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index d49736f..b6ed22e 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -122,9 +122,16 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
>                return 0;
>
>        if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
> -               unsigned long n;
> +               free = global_page_state(NR_FREE_PAGES);
> +               free += global_page_state(NR_FILE_PAGES);
> +
> +               /* shmem pages shouldn't be counted as free in this

Nitpick.
You didn't correct comment style. It's not a linux kernel coding style.

-- 
Kind regards,
Minchan Kim
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