From: Minchan Kim <minchan@kernel.org> To: Andrew Morton <akpm@linux-foundation.org> Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team <kernel-team@lge.com>, Minchan Kim <minchan@kernel.org>, Huang Ying <ying.huang@intel.com>, Hugh Dickins <hughd@google.com> Subject: [PATCH] mm:swap: skip swapcache only if swapped page has no other reference Date: Tue, 10 Oct 2017 16:33:45 +0900 Message-ID: <1507620825-5537-1-git-send-email-minchan@kernel.org> (raw) When 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. Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Minchan Kim <minchan@kernel.org> --- include/linux/swap.h | 6 ++++++ mm/memory.c | 19 ++++++++++--------- mm/swapfile.c | 7 +++++++ 3 files changed, 23 insertions(+), 9 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index cd2f66fdfc2d..1f5c52313890 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -458,6 +458,7 @@ 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 *); @@ -584,6 +585,11 @@ 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 163ab2062385..aff7e324564f 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 64a3d85226ba..d67715ffc194 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; -- 2.7.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
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