From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EFC2BCD98FE for ; Wed, 11 Oct 2023 08:17:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344796AbjJKIRw (ORCPT ); Wed, 11 Oct 2023 04:17:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36126 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229977AbjJKIRu (ORCPT ); Wed, 11 Oct 2023 04:17:50 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F36289E for ; Wed, 11 Oct 2023 01:17:48 -0700 (PDT) Received: from dggpemm100001.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4S559y1KyVzvPtg; Wed, 11 Oct 2023 16:13:10 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemm100001.china.huawei.com (7.185.36.93) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Wed, 11 Oct 2023 16:17:46 +0800 Message-ID: <75b3f607-856c-4210-9a7f-1a9535275698@huawei.com> Date: Wed, 11 Oct 2023 16:17:45 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1 1/2] mm: swap: Remove CLUSTER_FLAG_HUGE from swap_cluster_info:flags Content-Language: en-US To: Ryan Roberts , Andrew Morton , David Hildenbrand , Matthew Wilcox , Huang Ying , Gao Xiang , Yu Zhao , Yang Shi , Michal Hocko CC: , References: <20231010142111.3997780-1-ryan.roberts@arm.com> <20231010142111.3997780-2-ryan.roberts@arm.com> From: Kefeng Wang In-Reply-To: <20231010142111.3997780-2-ryan.roberts@arm.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm100001.china.huawei.com (7.185.36.93) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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().