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 --- mm/swapfile.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'mm/swapfile.c') diff --git a/mm/swapfile.c b/mm/swapfile.c index cb08fa65819f..85aff8a42801 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -3455,10 +3455,15 @@ int swapcache_prepare(swp_entry_t entry) return __swap_duplicate(entry, SWAP_HAS_CACHE); } +struct swap_info_struct *swp_swap_info(swp_entry_t entry) +{ + return swap_info[swp_type(entry)]; +} + struct swap_info_struct *page_swap_info(struct page *page) { - swp_entry_t swap = { .val = page_private(page) }; - return swap_info[swp_type(swap)]; + swp_entry_t entry = { .val = page_private(page) }; + return swp_swap_info(entry); } /* @@ -3466,7 +3471,6 @@ struct swap_info_struct *page_swap_info(struct page *page) */ struct address_space *__page_file_mapping(struct page *page) { - VM_BUG_ON_PAGE(!PageSwapCache(page), page); return page_swap_info(page)->swap_file->f_mapping; } EXPORT_SYMBOL_GPL(__page_file_mapping); @@ -3474,7 +3478,6 @@ EXPORT_SYMBOL_GPL(__page_file_mapping); pgoff_t __page_file_index(struct page *page) { swp_entry_t swap = { .val = page_private(page) }; - VM_BUG_ON_PAGE(!PageSwapCache(page), page); return swp_offset(swap); } EXPORT_SYMBOL_GPL(__page_file_index); -- cgit v1.2.3-55-g7522