From f4c4a3f48480730214c4f02ffa480f6bf5b0718f Mon Sep 17 00:00:00 2001 From: Huang Ying Date: Mon, 28 Jun 2021 19:37:12 -0700 Subject: [PATCH] mm: free idle swap cache page after COW With commit 09854ba94c6a ("mm: do_wp_page() simplification"), after COW, the idle swap cache page (neither the page nor the corresponding swap entry is mapped by any process) will be left in the LRU list, even if it's in the active list or the head of the inactive list. So, the page reclaimer may take quite some overhead to reclaim these actually unused pages. To help the page reclaiming, in this patch, after COW, the idle swap cache page will be tried to be freed. To avoid to introduce much overhead to the hot COW code path, a) there's almost zero overhead for non-swap case via checking PageSwapCache() firstly. b) the page lock is acquired via trylock only. To test the patch, we used pmbench memory accessing benchmark with working-set larger than available memory on a 2-socket Intel server with a NVMe SSD as swap device. Test results shows that the pmbench score increases up to 23.8% with the decreased size of swap cache and swapin throughput. Link: https://lkml.kernel.org/r/20210601053143.1380078-1-ying.huang@intel.com Signed-off-by: "Huang, Ying" Suggested-by: Johannes Weiner [use free_swap_cache()] Acked-by: Johannes Weiner Cc: Hugh Dickins Cc: Matthew Wilcox Cc: Peter Xu Cc: Mel Gorman Cc: Rik van Riel Cc: Andrea Arcangeli Cc: Michal Hocko Cc: Dave Hansen Cc: Tim Chen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/swap.h | 5 +++++ mm/memory.c | 2 ++ mm/swap_state.c | 2 +- 3 files changed, 8 insertions(+), 1 deletion(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 46d51d0..49b1dd2 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -446,6 +446,7 @@ extern void __delete_from_swap_cache(struct page *page, extern void delete_from_swap_cache(struct page *); extern void clear_shadow_from_swap_cache(int type, unsigned long begin, unsigned long end); +extern void free_swap_cache(struct page *); extern void free_page_and_swap_cache(struct page *); extern void free_pages_and_swap_cache(struct page **, int); extern struct page *lookup_swap_cache(swp_entry_t entry, @@ -551,6 +552,10 @@ static inline void put_swap_device(struct swap_info_struct *si) #define free_pages_and_swap_cache(pages, nr) \ release_pages((pages), (nr)); +static inline void free_swap_cache(struct page *page) +{ +} + static inline void show_swap_cache_info(void) { } diff --git a/mm/memory.c b/mm/memory.c index b15367c..a4d82a6 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3023,6 +3023,8 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) munlock_vma_page(old_page); unlock_page(old_page); } + if (page_copied) + free_swap_cache(old_page); put_page(old_page); } return page_copied ? VM_FAULT_WRITE : 0; diff --git a/mm/swap_state.c b/mm/swap_state.c index 1a2ba40..4f8a912 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -286,7 +286,7 @@ void clear_shadow_from_swap_cache(int type, unsigned long begin, * try_to_free_swap() _with_ the lock. * - Marcelo */ -static inline void free_swap_cache(struct page *page) +void free_swap_cache(struct page *page) { if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) { try_to_free_swap(page); -- 2.7.4