diff options
| author | Minchan Kim <minchan@kernel.org> | 2017-11-15 17:33:11 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-11-15 18:21:02 -0800 |
| commit | aa8d22a11da933dbf880b4933b58931f4aefe91c (patch) | |
| tree | ed7a7c1ecdfa4da6079858dfc0cfb6fbb65e3286 | |
| parent | 0bcac06f27d7528591c27ac2b093ccd71c5d0168 (diff) | |
mm: swap: SWP_SYNCHRONOUS_IO: skip swapcache only if swapped page has no other reference
When SWP_SYNCHRONOUS_IO swapped-in pages are shared by several
processes, it can cause unnecessary memory wastage by skipping swap
cache. Because, with swapin fault by read, they could share a page if
the page were in swap cache. Thus, it avoids allocating same content
new pages.
This patch makes the swapcache skipping work only if the swap pte is
non-sharable.
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/1507620825-5537-1-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | include/linux/swap.h | 6 | ||||
| -rw-r--r-- | mm/memory.c | 19 | ||||
| -rw-r--r-- | mm/swapfile.c | 7 |
3 files changed, 23 insertions, 9 deletions
diff --git a/include/linux/swap.h b/include/linux/swap.h index 32c06f028c7b..8b8a6f965785 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -463,6 +463,7 @@ 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 page_swapcount(struct page *); +extern int __swap_count(struct swap_info_struct *si, swp_entry_t entry); extern int __swp_swapcount(swp_entry_t entry); extern int swp_swapcount(swp_entry_t entry); extern struct swap_info_struct *page_swap_info(struct page *); @@ -589,6 +590,11 @@ static inline int page_swapcount(struct page *page) return 0; } +static inline int __swap_count(struct swap_info_struct *si, swp_entry_t entry) +{ + return 0; +} + static inline int __swp_swapcount(swp_entry_t entry) { return 0; diff --git a/mm/memory.c b/mm/memory.c index f75bff2cf662..a4518aedf4dd 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2890,15 +2890,8 @@ int do_swap_page(struct vm_fault *vmf) if (!page) { struct swap_info_struct *si = swp_swap_info(entry); - if (!(si->flags & SWP_SYNCHRONOUS_IO)) { - if (vma_readahead) - page = do_swap_page_readahead(entry, - GFP_HIGHUSER_MOVABLE, vmf, &swap_ra); - else - page = swapin_readahead(entry, - GFP_HIGHUSER_MOVABLE, vma, vmf->address); - swapcache = page; - } else { + if (si->flags & SWP_SYNCHRONOUS_IO && + __swap_count(si, entry) == 1) { /* skip swapcache */ page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vmf->address); if (page) { @@ -2908,6 +2901,14 @@ int do_swap_page(struct vm_fault *vmf) lru_cache_add_anon(page); swap_readpage(page, true); } + } else { + if (vma_readahead) + page = do_swap_page_readahead(entry, + GFP_HIGHUSER_MOVABLE, vmf, &swap_ra); + else + page = swapin_readahead(entry, + GFP_HIGHUSER_MOVABLE, vma, vmf->address); + swapcache = page; } if (!page) { diff --git a/mm/swapfile.c b/mm/swapfile.c index 85aff8a42801..3074b02eaa09 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1328,6 +1328,13 @@ int page_swapcount(struct page *page) return count; } +int __swap_count(struct swap_info_struct *si, swp_entry_t entry) +{ + pgoff_t offset = swp_offset(entry); + + return swap_count(si->swap_map[offset]); +} + static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry) { int count = 0; |