From 0bcac06f27d7528591c27ac2b093ccd71c5d0168 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Wed, 15 Nov 2017 17:33:07 -0800 Subject: mm, swap: skip swapcache for swapin of synchronous device With fast swap storage, the platforms want to use swap more aggressively and swap-in is crucial to application latency. The rw_page() based synchronous devices like zram, pmem and btt are such fast storage. When I profile swapin performance with zram lz4 decompress test, S/W overhead is more than 70%. Maybe, it would be bigger in nvdimm. This patch aims to reduce swap-in latency by skipping swapcache if the swap device is synchronous device like rw_page based device. It enhances 45% my swapin test(5G sequential swapin, no readahead, from 2.41sec to 1.64sec). Link: http://lkml.kernel.org/r/1505886205-9671-5-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim Cc: Dan Williams Cc: Ross Zwisler Cc: Hugh Dickins Cc: Christoph Hellwig Cc: Ilya Dryomov Cc: Jens Axboe Cc: Sergey Senozhatsky Cc: Huang Ying Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/swap.h | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'include/linux/swap.h') diff --git a/include/linux/swap.h b/include/linux/swap.h index 933d7c0c3542..32c06f028c7b 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -466,6 +466,7 @@ extern int page_swapcount(struct page *); 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 *); +extern struct swap_info_struct *swp_swap_info(swp_entry_t entry); extern bool reuse_swap_page(struct page *, int *); extern int try_to_free_swap(struct page *); struct backing_dev_info; @@ -474,6 +475,16 @@ extern void exit_swap_address_space(unsigned int type); #else /* CONFIG_SWAP */ +static inline int swap_readpage(struct page *page, bool do_poll) +{ + return 0; +} + +static inline struct swap_info_struct *swp_swap_info(swp_entry_t entry) +{ + return NULL; +} + #define swap_address_space(entry) (NULL) #define get_nr_swap_pages() 0L #define total_swap_pages 0L -- cgit v1.2.3