From 0bcac06f27d7528591c27ac2b093ccd71c5d0168 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Wed, 15 Nov 2017 17:33:07 -0800 Subject: [PATCH] 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 ++++++++++ mm/memory.c | 52 ++++++++++++++++++++++++++++++-------------- mm/page_io.c | 6 ++--- mm/swapfile.c | 11 ++++++---- 4 files changed, 57 insertions(+), 23 deletions(-) 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 diff --git a/mm/memory.c b/mm/memory.c index cae514e7dcfc..f75bff2cf662 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2842,7 +2842,7 @@ EXPORT_SYMBOL(unmap_mapping_range); int do_swap_page(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; - struct page *page = NULL, *swapcache; + struct page *page = NULL, *swapcache = NULL; struct mem_cgroup *memcg; struct vma_swap_readahead swap_ra; swp_entry_t entry; @@ -2881,17 +2881,35 @@ int do_swap_page(struct vm_fault *vmf) } goto out; } + + delayacct_set_flag(DELAYACCT_PF_SWAPIN); if (!page) page = lookup_swap_cache(entry, vma_readahead ? vma : NULL, vmf->address); if (!page) { - if (vma_readahead) - page = do_swap_page_readahead(entry, - GFP_HIGHUSER_MOVABLE, vmf, &swap_ra); - else - page = swapin_readahead(entry, - GFP_HIGHUSER_MOVABLE, vma, vmf->address); + struct swap_info_struct *si = swp_swap_info(entry); + + if (!(si->flags & SWP_SYNCHRONOUS_IO)) { + if (vma_readahead) + page = do_swap_page_readahead(entry, + GFP_HIGHUSER_MOVABLE, vmf, &swap_ra); + else + page = swapin_readahead(entry, + GFP_HIGHUSER_MOVABLE, vma, vmf->address); + swapcache = page; + } else { + /* skip swapcache */ + page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vmf->address); + if (page) { + __SetPageLocked(page); + __SetPageSwapBacked(page); + set_page_private(page, entry.val); + lru_cache_add_anon(page); + swap_readpage(page, true); + } + } + if (!page) { /* * Back out if somebody else faulted in this pte @@ -2920,7 +2938,6 @@ int do_swap_page(struct vm_fault *vmf) goto out_release; } - swapcache = page; locked = lock_page_or_retry(page, vma->vm_mm, vmf->flags); delayacct_clear_flag(DELAYACCT_PF_SWAPIN); @@ -2935,7 +2952,8 @@ int do_swap_page(struct vm_fault *vmf) * test below, are not enough to exclude that. Even if it is still * swapcache, we need to check that the page's swap has not changed. */ - if (unlikely(!PageSwapCache(page) || page_private(page) != entry.val)) + if (unlikely((!PageSwapCache(page) || + page_private(page) != entry.val)) && swapcache) goto out_page; page = ksm_might_need_to_copy(page, vma, vmf->address); @@ -2988,14 +3006,16 @@ int do_swap_page(struct vm_fault *vmf) pte = pte_mksoft_dirty(pte); set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte); vmf->orig_pte = pte; - if (page == swapcache) { - do_page_add_anon_rmap(page, vma, vmf->address, exclusive); - mem_cgroup_commit_charge(page, memcg, true, false); - activate_page(page); - } else { /* ksm created a completely new copy */ + + /* ksm created a completely new copy */ + if (unlikely(page != swapcache && swapcache)) { page_add_new_anon_rmap(page, vma, vmf->address, false); mem_cgroup_commit_charge(page, memcg, false, false); lru_cache_add_active_or_unevictable(page, vma); + } else { + do_page_add_anon_rmap(page, vma, vmf->address, exclusive); + mem_cgroup_commit_charge(page, memcg, true, false); + activate_page(page); } swap_free(entry); @@ -3003,7 +3023,7 @@ int do_swap_page(struct vm_fault *vmf) (vma->vm_flags & VM_LOCKED) || PageMlocked(page)) try_to_free_swap(page); unlock_page(page); - if (page != swapcache) { + if (page != swapcache && swapcache) { /* * Hold the lock to avoid the swap entry to be reused * until we take the PT lock for the pte_same() check @@ -3036,7 +3056,7 @@ int do_swap_page(struct vm_fault *vmf) unlock_page(page); out_release: put_page(page); - if (page != swapcache) { + if (page != swapcache && swapcache) { unlock_page(swapcache); put_page(swapcache); } diff --git a/mm/page_io.c b/mm/page_io.c index cd52b9cc169b..e93f1a4cacd7 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -347,7 +347,7 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc, return ret; } -int swap_readpage(struct page *page, bool do_poll) +int swap_readpage(struct page *page, bool synchronous) { struct bio *bio; int ret = 0; @@ -355,7 +355,7 @@ int swap_readpage(struct page *page, bool do_poll) blk_qc_t qc; struct gendisk *disk; - VM_BUG_ON_PAGE(!PageSwapCache(page), page); + VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page); VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(PageUptodate(page), page); if (frontswap_load(page) == 0) { @@ -403,7 +403,7 @@ int swap_readpage(struct page *page, bool do_poll) count_vm_event(PSWPIN); bio_get(bio); qc = submit_bio(bio); - while (do_poll) { + while (synchronous) { set_current_state(TASK_UNINTERRUPTIBLE); if (!READ_ONCE(bio->bi_private)) break; 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);