Messages in this thread | | | Date | Wed, 11 Oct 2023 16:17:45 +0800 | Subject | Re: [RFC PATCH v1 1/2] mm: swap: Remove CLUSTER_FLAG_HUGE from swap_cluster_info:flags | From | Kefeng Wang <> |
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On 2023/10/10 22:21, Ryan Roberts wrote: > 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 > avoid bothering to 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 equivalent. > > 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 <ryan.roberts@arm.com> > --- > 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 19f30a29e1f1..a073366a227c 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 > @@ -595,15 +594,6 @@ 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 c9cbcbf6697e..46b3fb943207 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2597,9 +2597,6 @@ static void __split_huge_page(struct page *page, struct list_head *list, > shmem_uncharge(head->mapping->host, nr_dropped); > remap_page(folio, nr); > > - if (folio_test_swapcache(folio)) > - split_swap_cluster(folio->swap); > - > for (i = 0; i < nr; i++) { > struct page *subpage = head + i; > if (subpage == page) > diff --git a/mm/swapfile.c b/mm/swapfile.c > index e52f486834eb..c668838fa660 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -342,18 +342,6 @@ 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) > { > @@ -1021,7 +1009,7 @@ 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_flag(ci, SWAPFILE_CLUSTER, 0);
Maybe just use cluster_set_count() and kill cluster_set_count_flag().
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