On Sun, 10 Jul 2011, Dmitry Fink 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@xxxxxxxx>
> Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
> Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Just right: thanks a lot for redoing it this way, Dmitry.
> ---
> mm/mmap.c | 34 +++++++++++++---------------------
> mm/nommu.c | 34 +++++++++++++---------------------
> 2 files changed, 26 insertions(+), 42 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index d49736f..a65efd4 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -122,9 +122,17 @@ 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
> + * case, they can't be purged, only swapped out, and
> + * that won't affect the overall amount of available
> + * memory in the system.
> + */
> + free -= global_page_state(NR_SHMEM);
>
> - free = global_page_state(NR_FILE_PAGES);
> free += nr_swap_pages;
>
> /*
> @@ -136,34 +144,18 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
> free += global_page_state(NR_SLAB_RECLAIMABLE);
>
> /*
> - * Leave the last 3% for root
> - */
> - if (!cap_sys_admin)
> - free -= free / 32;
> -
> - if (free > pages)
> - return 0;
> -
> - /*
> - * nr_free_pages() is very expensive on large systems,
> - * only call if we're about to fail.
> - */
> - n = nr_free_pages();
> -
> - /*
> * Leave reserved pages. The pages are not for anonymous pages.
> */
> - if (n <= totalreserve_pages)
> + if (free <= totalreserve_pages)
> goto error;
> else
> - n -= totalreserve_pages;
> + free -= totalreserve_pages;
>
> /*
> * Leave the last 3% for root
> */
> if (!cap_sys_admin)
> - n -= n / 32;
> - free += n;
> + free -= free / 32;
>
> if (free > pages)
> return 0;
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 9edc897..76f2b4b 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -1885,9 +1885,17 @@ 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
> + * case, they can't be purged, only swapped out, and
> + * that won't affect the overall amount of available
> + * memory in the system.
> + */
> + free -= global_page_state(NR_SHMEM);
>
> - free = global_page_state(NR_FILE_PAGES);
> free += nr_swap_pages;
>
> /*
> @@ -1899,34 +1907,18 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
> free += global_page_state(NR_SLAB_RECLAIMABLE);
>
> /*
> - * Leave the last 3% for root
> - */
> - if (!cap_sys_admin)
> - free -= free / 32;
> -
> - if (free > pages)
> - return 0;
> -
> - /*
> - * nr_free_pages() is very expensive on large systems,
> - * only call if we're about to fail.
> - */
> - n = nr_free_pages();
> -
> - /*
> * Leave reserved pages. The pages are not for anonymous pages.
> */
> - if (n <= totalreserve_pages)
> + if (free <= totalreserve_pages)
> goto error;
> else
> - n -= totalreserve_pages;
> + free -= totalreserve_pages;
>
> /*
> * Leave the last 3% for root
> */
> if (!cap_sys_admin)
> - n -= n / 32;
> - free += n;
> + free -= free / 32;
>
> if (free > pages)
> return 0;
> --
> 1.7.6
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