From 018ee47f14893d500131dfca2ff9f3ff8ebd4ed2 Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Sun, 18 Sep 2022 02:00:04 -0600 Subject: mm: multi-gen LRU: exploit locality in rmap MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Searching the rmap for PTEs mapping each page on an LRU list (to test and clear the accessed bit) can be expensive because pages from different VMAs (PA space) are not cache friendly to the rmap (VA space). For workloads mostly using mapped pages, searching the rmap can incur the highest CPU cost in the reclaim path. This patch exploits spatial locality to reduce the trips into the rmap. When shrink_page_list() walks the rmap and finds a young PTE, a new function lru_gen_look_around() scans at most BITS_PER_LONG-1 adjacent PTEs. On finding another young PTE, it clears the accessed bit and updates the gen counter of the page mapped by this PTE to (max_seq%MAX_NR_GENS)+1. Server benchmark results: Single workload: fio (buffered I/O): no change Single workload: memcached (anon): +[3, 5]% Ops/sec KB/sec patch1-6: 1106168.46 43025.04 patch1-7: 1147696.57 44640.29 Configurations: no change Client benchmark results: kswapd profiles: patch1-6 39.03% lzo1x_1_do_compress (real work) 18.47% page_vma_mapped_walk (overhead) 6.74% _raw_spin_unlock_irq 3.97% do_raw_spin_lock 2.49% ptep_clear_flush 2.48% anon_vma_interval_tree_iter_first 1.92% folio_referenced_one 1.88% __zram_bvec_write 1.48% memmove 1.31% vma_interval_tree_iter_next patch1-7 48.16% lzo1x_1_do_compress (real work) 8.20% page_vma_mapped_walk (overhead) 7.06% _raw_spin_unlock_irq 2.92% ptep_clear_flush 2.53% __zram_bvec_write 2.11% do_raw_spin_lock 2.02% memmove 1.93% lru_gen_look_around 1.56% free_unref_page_list 1.40% memset Configurations: no change Link: https://lkml.kernel.org/r/20220918080010.2920238-8-yuzhao@google.com Signed-off-by: Yu Zhao Acked-by: Barry Song Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Cc: Andi Kleen Cc: Aneesh Kumar K.V Cc: Catalin Marinas Cc: Dave Hansen Cc: Hillf Danton Cc: Jens Axboe Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Linus Torvalds Cc: Matthew Wilcox Cc: Mel Gorman Cc: Miaohe Lin Cc: Michael Larabel Cc: Michal Hocko Cc: Mike Rapoport Cc: Mike Rapoport Cc: Peter Zijlstra Cc: Qi Zheng Cc: Tejun Heo Cc: Vlastimil Babka Cc: Will Deacon Signed-off-by: Andrew Morton --- include/linux/mmzone.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/linux/mmzone.h') diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 7e343420bfb1..9ef5aa37c60c 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -375,6 +375,7 @@ enum lruvec_flags { #ifndef __GENERATING_BOUNDS_H struct lruvec; +struct page_vma_mapped_walk; #define LRU_GEN_MASK ((BIT(LRU_GEN_WIDTH) - 1) << LRU_GEN_PGOFF) #define LRU_REFS_MASK ((BIT(LRU_REFS_WIDTH) - 1) << LRU_REFS_PGOFF) @@ -430,6 +431,7 @@ struct lru_gen_struct { }; void lru_gen_init_lruvec(struct lruvec *lruvec); +void lru_gen_look_around(struct page_vma_mapped_walk *pvmw); #ifdef CONFIG_MEMCG void lru_gen_init_memcg(struct mem_cgroup *memcg); @@ -442,6 +444,10 @@ static inline void lru_gen_init_lruvec(struct lruvec *lruvec) { } +static inline void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) +{ +} + #ifdef CONFIG_MEMCG static inline void lru_gen_init_memcg(struct mem_cgroup *memcg) { -- cgit v1.2.3