Commit aa8d22a1 authored by Minchan Kim's avatar Minchan Kim Committed by Linus Torvalds
Browse files

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: default avatarMinchan 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0bcac06f

include/linux/swap.h

+6 −0
Original line number Diff line number Diff line
@@ -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;

mm/memory.c

+10 −9
Original line number Diff line number Diff line
@@ -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) {

mm/swapfile.c

+7 −0
Original line number Diff line number Diff line
@@ -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;

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