The patch titled
mmap: fix and tidy up overcommit page arithmetic
has been added to the -mm tree. Its filename is
mmap-fix-and-tidy-up-overcommit-page-arithmetic.patch
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------------------------------------------------------
Subject: mmap: fix and tidy up overcommit page arithmetic
From: Dmitry Fink <dmitry.fink@xxxxxxxx>
- 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>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 34 +++++++++++++---------------------
mm/nommu.c | 34 +++++++++++++---------------------
2 files changed, 26 insertions(+), 42 deletions(-)
diff -puN mm/mmap.c~mmap-fix-and-tidy-up-overcommit-page-arithmetic mm/mmap.c
--- a/mm/mmap.c~mmap-fix-and-tidy-up-overcommit-page-arithmetic
+++ a/mm/mmap.c
@@ -122,9 +122,17 @@ int __vm_enough_memory(struct mm_struct
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
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 -puN mm/nommu.c~mmap-fix-and-tidy-up-overcommit-page-arithmetic mm/nommu.c
--- a/mm/nommu.c~mmap-fix-and-tidy-up-overcommit-page-arithmetic
+++ a/mm/nommu.c
@@ -1884,9 +1884,17 @@ int __vm_enough_memory(struct mm_struct
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
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;
_
Patches currently in -mm which might be from dmitry.fink@xxxxxxxx are
mmap-fix-and-tidy-up-overcommit-page-arithmetic.patch
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