From c15bef3099c346f2124367bff46954b59e13c3ee Mon Sep 17 00:00:00 2001 From: Dmitry Fink Date: Mon, 25 Jul 2011 17:12:19 -0700 Subject: [PATCH] mmap: fix and tidy up overcommit page arithmetic - 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 Reviewed-by: Minchan Kim Acked-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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 d49736ff8a8d..a65efd4db3e1 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; /* @@ -135,35 +143,19 @@ 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 5c5c2d4b1807..4358032566e9 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1884,9 +1884,17 @@ 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; /* @@ -1897,35 +1905,19 @@ 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; -- 2.20.1