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authorDmitry Fink <dmitry.fink@palm.com>2011-07-25 17:12:19 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-07-25 20:57:09 -0700
commitc15bef3099c346f2124367bff46954b59e13c3ee (patch)
treeec09c0b25eae42d6693a08decde7aee02f296978 /mm/nommu.c
parentc9d8c3d0896bfa5b57531ecc41a85ffbc6d87dbe (diff)
downloadlwn-c15bef3099c346f2124367bff46954b59e13c3ee.tar.gz
lwn-c15bef3099c346f2124367bff46954b59e13c3ee.zip
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 <dmitry.fink@palm.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Acked-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/nommu.c')
-rw-r--r--mm/nommu.c34
1 files changed, 13 insertions, 21 deletions
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;
/*
@@ -1898,34 +1906,18 @@ 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;