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Mon, 11 Mar 2024 08:01:10 -0700 (PDT) From: Ryan Roberts To: Andrew Morton , David Hildenbrand , Matthew Wilcox , Huang Ying , Gao Xiang , Yu Zhao , Yang Shi , Michal Hocko , Kefeng Wang , Barry Song <21cnbao@gmail.com>, Chris Li Cc: Ryan Roberts , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 1/6] mm: swap: Remove CLUSTER_FLAG_HUGE from swap_cluster_info:flags Date: Mon, 11 Mar 2024 15:00:53 +0000 Message-Id: <20240311150058.1122862-2-ryan.roberts@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20240311150058.1122862-1-ryan.roberts@arm.com> References: <20240311150058.1122862-1-ryan.roberts@arm.com> MIME-Version: 1.0 X-Rspam-User: X-Stat-Signature: w946ppqd4dwc6xnowswz8fbzy3eirm3h X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 8D13C2002A X-HE-Tag: 1710169273-952165 X-HE-Meta: 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 a3xiWso7 YukIL3L/o1jt5irxSSffAQj7mYzsu1hizs/7XtUuLpi5cEdepObf1y3Ht5kfKANDDadML4A6XmKK8BXji1ohOYwimN67lBFEYc+UjLXao5Y64U1KWaz01Q4QX8j6eaz6oyaxihZ/6cCUGeaZbCwynDsvLZC28TWlvSyFgaBoSDuqQ+c4LSFM7l0fdRPMCyrljRNVR5KfXL4jYqSE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: As preparation for supporting small-sized THP in the swap-out path, without first needing to split to order-0, Remove the CLUSTER_FLAG_HUGE, which, when present, always implies PMD-sized THP, which is the same as the cluster size. The only use of the flag was to determine whether a swap entry refers to a single page or a PMD-sized THP in swap_page_trans_huge_swapped(). Instead of relying on the flag, we now pass in nr_pages, which originates from the folio's number of pages. This allows the logic to work for folios of any order. The one snag is that one of the swap_page_trans_huge_swapped() call sites does not have the folio. But it was only being called there to shortcut a call __try_to_reclaim_swap() in some cases. __try_to_reclaim_swap() gets the folio and (via some other functions) calls swap_page_trans_huge_swapped(). So I've removed the problematic call site and believe the new logic should be functionally equivalent. That said, removing the fast path means that we will take a reference and trylock a large folio much more often, which we would like to avoid. The next patch will solve this. Removing CLUSTER_FLAG_HUGE also means we can remove split_swap_cluster() which used to be called during folio splitting, since split_swap_cluster()'s only job was to remove the flag. Signed-off-by: Ryan Roberts --- include/linux/swap.h | 10 ---------- mm/huge_memory.c | 3 --- mm/swapfile.c | 47 ++++++++------------------------------------ 3 files changed, 8 insertions(+), 52 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 2955f7a78d8d..4a8b6c60793a 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -259,7 +259,6 @@ struct swap_cluster_info { }; #define CLUSTER_FLAG_FREE 1 /* This cluster is free */ #define CLUSTER_FLAG_NEXT_NULL 2 /* This cluster has no next cluster */ -#define CLUSTER_FLAG_HUGE 4 /* This cluster is backing a transparent huge page */ /* * We assign a cluster to each CPU, so each CPU can allocate swap entry from @@ -600,15 +599,6 @@ static inline int add_swap_extent(struct swap_info_struct *sis, } #endif /* CONFIG_SWAP */ -#ifdef CONFIG_THP_SWAP -extern int split_swap_cluster(swp_entry_t entry); -#else -static inline int split_swap_cluster(swp_entry_t entry) -{ - return 0; -} -#endif - #ifdef CONFIG_MEMCG static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg) { diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 04fb994a7b0b..5298ba882d49 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2965,9 +2965,6 @@ static void __split_huge_page(struct page *page, struct list_head *list, shmem_uncharge(folio->mapping->host, nr_dropped); remap_page(folio, nr); - if (folio_test_swapcache(folio)) - split_swap_cluster(folio->swap); - /* * set page to its compound_head when split to non order-0 pages, so * we can skip unlocking it below, since PG_locked is transferred to diff --git a/mm/swapfile.c b/mm/swapfile.c index 1155a6304119..df1de034f6d8 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -343,18 +343,6 @@ static inline void cluster_set_null(struct swap_cluster_info *info) info->data = 0; } -static inline bool cluster_is_huge(struct swap_cluster_info *info) -{ - if (IS_ENABLED(CONFIG_THP_SWAP)) - return info->flags & CLUSTER_FLAG_HUGE; - return false; -} - -static inline void cluster_clear_huge(struct swap_cluster_info *info) -{ - info->flags &= ~CLUSTER_FLAG_HUGE; -} - static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si, unsigned long offset) { @@ -1027,7 +1015,7 @@ static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot) offset = idx * SWAPFILE_CLUSTER; ci = lock_cluster(si, offset); alloc_cluster(si, idx); - cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE); + cluster_set_count(ci, SWAPFILE_CLUSTER); memset(si->swap_map + offset, SWAP_HAS_CACHE, SWAPFILE_CLUSTER); unlock_cluster(ci); @@ -1365,7 +1353,6 @@ void put_swap_folio(struct folio *folio, swp_entry_t entry) ci = lock_cluster_or_swap_info(si, offset); if (size == SWAPFILE_CLUSTER) { - VM_BUG_ON(!cluster_is_huge(ci)); map = si->swap_map + offset; for (i = 0; i < SWAPFILE_CLUSTER; i++) { val = map[i]; @@ -1373,7 +1360,6 @@ void put_swap_folio(struct folio *folio, swp_entry_t entry) if (val == SWAP_HAS_CACHE) free_entries++; } - cluster_clear_huge(ci); if (free_entries == SWAPFILE_CLUSTER) { unlock_cluster_or_swap_info(si, ci); spin_lock(&si->lock); @@ -1395,23 +1381,6 @@ void put_swap_folio(struct folio *folio, swp_entry_t entry) unlock_cluster_or_swap_info(si, ci); } -#ifdef CONFIG_THP_SWAP -int split_swap_cluster(swp_entry_t entry) -{ - struct swap_info_struct *si; - struct swap_cluster_info *ci; - unsigned long offset = swp_offset(entry); - - si = _swap_info_get(entry); - if (!si) - return -EBUSY; - ci = lock_cluster(si, offset); - cluster_clear_huge(ci); - unlock_cluster(ci); - return 0; -} -#endif - static int swp_entry_cmp(const void *ent1, const void *ent2) { const swp_entry_t *e1 = ent1, *e2 = ent2; @@ -1519,22 +1488,23 @@ int swp_swapcount(swp_entry_t entry) } static bool swap_page_trans_huge_swapped(struct swap_info_struct *si, - swp_entry_t entry) + swp_entry_t entry, + unsigned int nr_pages) { struct swap_cluster_info *ci; unsigned char *map = si->swap_map; unsigned long roffset = swp_offset(entry); - unsigned long offset = round_down(roffset, SWAPFILE_CLUSTER); + unsigned long offset = round_down(roffset, nr_pages); int i; bool ret = false; ci = lock_cluster_or_swap_info(si, offset); - if (!ci || !cluster_is_huge(ci)) { + if (!ci || nr_pages == 1) { if (swap_count(map[roffset])) ret = true; goto unlock_out; } - for (i = 0; i < SWAPFILE_CLUSTER; i++) { + for (i = 0; i < nr_pages; i++) { if (swap_count(map[offset + i])) { ret = true; break; @@ -1556,7 +1526,7 @@ static bool folio_swapped(struct folio *folio) if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!folio_test_large(folio))) return swap_swapcount(si, entry) != 0; - return swap_page_trans_huge_swapped(si, entry); + return swap_page_trans_huge_swapped(si, entry, folio_nr_pages(folio)); } /** @@ -1622,8 +1592,7 @@ int free_swap_and_cache(swp_entry_t entry) } count = __swap_entry_free(p, entry); - if (count == SWAP_HAS_CACHE && - !swap_page_trans_huge_swapped(p, entry)) + if (count == SWAP_HAS_CACHE) __try_to_reclaim_swap(p, swp_offset(entry), TTRS_UNMAPPED | TTRS_FULL); put_swap_device(p);