mm: Handle misplaced anon pages
Subsystems (3)
Commit-ID: 65699050e8aae41078c9c73f61f6fae26e07e461 Gitweb: http://git.kernel.org/tip/65699050e8aae41078c9c73f61f6fae26e07e461 Author: Lee Schermerhorn <[email protected]> AuthorDate: Thu, 12 Jan 2012 12:05:17 +0100 Committer: Ingo Molnar <[email protected]> CommitDate: Fri, 18 May 2012 08:16:18 +0200
mm: Handle misplaced anon pages
This patch simply hooks the anon page fault handler [do_swap_page()] to check for and migrate misplaced pages if enabled and page won't be "COWed".
This introduces can_reuse_swap_page() since reuse_swap_page() does delete_from_swap_cache() which messes our migration path (since that assumes its still a swapcache page).
Signed-off-by Lee Schermerhorn <[email protected]>
[ removed the retry loops after lock_page on a swapcache which tried
to fixup the wreckage caused by ignoring the page count on migate; added can_reuse_swap_page(); moved the migrate-on-fault enabled test into check_migrate_misplaced_page() ]
Signed-off-by Peter Zijlstra <[email protected]>
Cc Suresh Siddha <[email protected]>
Cc Paul Turner <[email protected]>
Cc Dan Smith <[email protected]>
Cc Bharata B Rao <[email protected]>
Cc Christoph Lameter <[email protected]>
Cc Rik van Riel <[email protected]>
Cc Andrea Arcangeli <[email protected]>
Cc Andrew Morton <[email protected]>
Cc Linus Torvalds <[email protected]>
Signed-off-by Ingo Molnar <[email protected]>
--- include/linux/swap.h | 4 +++- mm/memory.c | 17 +++++++++++++++++ mm/swapfile.c | 13 +++++++++++++ 3 files changed, 33 insertions(+), 1 deletions(-)
include/linux/swap.h +3 -1
@@ -352,6 +352,7 @@ extern unsigned int count_swap_pages(int, int);extern sector_t map_swap_page (struct page *,struct block_device **);extern sector_t swapdev_block (int ,pgoff_t );extern int reuse_swap_page (struct page *); +extern int can_reuse_swap_page (struct page *);extern int try_to_free_swap (struct page *);struct backing_dev_info ;
@@ -462,7 +463,8 @@ static inline void delete_from_swap_cache(struct page *page) { } -#define reuse_swap_page (page) (page_mapcount(page) == 1) +#define reuse_swap_page (page) (page_mapcount(page) == 1) +#define can_reuse_swap_page (page) (page_mapcount(page) == 1)static inline int try_to_free_swap (struct page *page) {
mm/memory.c +17 -0
@@ -57,6 +57,7 @@#include <linux/swapops.h> #include <linux/elf.h> #include <linux/gfp.h> +#include <linux/mempolicy.h> /* check_migrate_misplaced_page() */ #include <asm/io.h> #include <asm/pgalloc.h>
@@ -2974,6 +2975,22 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, }/* +* No sense in migrating a page that will be "COWed" as the new +* new page will be allocated according to effective mempolicy. +*/ +if ((flags &FAULT_FLAG_WRITE ) &&can_reuse_swap_page (page)) { +/* +* check for misplacement and migrate, if necessary/possible, +* here and now. Note that if we're racing with another thread, +* we may end up discarding the migrated page after locking +* the page table and checking the pte below. However, we +* don't want to hold the page table locked over migration, so +* we'll live with that [unlikely, one hopes] possibility. +*/ + page =check_migrate_misplaced_page (page, vma, address); + } + +/* * Back out if somebody else already faulted in this pte. */ page_table =pte_offset_map_lock (mm, pmd, address, &ptl);
mm/swapfile.c +13 -0
@@ -640,6 +640,19 @@ int reuse_swap_page(struct page *page)return count <=1 ; } +int can_reuse_swap_page (struct page *page) +{ +int count; + +VM_BUG_ON (!PageLocked (page)); +if (unlikely (PageKsm (page))) +return 0 ; + count =page_mapcount (page); +if (count <=1 &&PageSwapCache (page)) + count +=page_swapcount (page); +return count <=1 ; +} +/* * If swap is getting full, or if there are no more mappings of this page, * then try_to_free_swap is called to free its swap space.