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authorMinchan Kim <minchan@kernel.org>2017-11-16 04:33:11 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-16 05:21:02 +0300
commitaa8d22a11da933dbf880b4933b58931f4aefe91c (patch)
treeed7a7c1ecdfa4da6079858dfc0cfb6fbb65e3286 /mm/swapfile.c
parent0bcac06f27d7528591c27ac2b093ccd71c5d0168 (diff)
downloadlinux-aa8d22a11da933dbf880b4933b58931f4aefe91c.tar.xz
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>
Diffstat (limited to 'mm/swapfile.c')
-rw-r--r--mm/swapfile.c7
1 files changed, 7 insertions, 0 deletions
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;