From: Kefeng Wang <wangkefeng.wang@huawei.com>
To: Ryan Roberts <ryan.roberts@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Huang Ying <ying.huang@intel.com>, Gao Xiang <xiang@kernel.org>,
Yu Zhao <yuzhao@google.com>, Yang Shi <shy828301@gmail.com>,
Michal Hocko <mhocko@suse.com>
Cc: <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
Subject: Re: [RFC PATCH v1 1/2] mm: swap: Remove CLUSTER_FLAG_HUGE from swap_cluster_info:flags
Date: Wed, 11 Oct 2023 16:17:45 +0800 [thread overview]
Message-ID: <75b3f607-856c-4210-9a7f-1a9535275698@huawei.com> (raw)
In-Reply-To: <20231010142111.3997780-2-ryan.roberts@arm.com>
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().
next prev parent reply other threads:[~2023-10-11 8:42 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-10 14:21 [RFC PATCH v1 0/2] Swap-out small-sized THP without splitting Ryan Roberts
2023-10-10 14:21 ` [RFC PATCH v1 1/2] mm: swap: Remove CLUSTER_FLAG_HUGE from swap_cluster_info:flags Ryan Roberts
2023-10-11 7:43 ` Huang, Ying
2023-10-11 8:17 ` Kefeng Wang [this message]
2023-10-11 10:15 ` Ryan Roberts
2023-10-11 10:16 ` Ryan Roberts
2023-10-10 14:21 ` [RFC PATCH v1 2/2] mm: swap: Swap-out small-sized THP without splitting Ryan Roberts
2023-10-11 7:44 ` Ryan Roberts
2023-10-11 8:25 ` Huang, Ying
2023-10-11 10:36 ` Ryan Roberts
2023-10-11 17:14 ` Ryan Roberts
2023-10-16 6:17 ` Huang, Ying
2023-10-16 12:10 ` Ryan Roberts
2023-10-17 5:44 ` Huang, Ying
2023-10-11 6:37 ` [RFC PATCH v1 0/2] " Huang, Ying
2023-10-11 7:42 ` Ryan Roberts
2023-10-13 16:31 ` Ryan Roberts
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