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Shuemov" , Ryan Roberts , Yang Shi , Yu Zhao Subject: [PATCH v3 2/2] mm/shmem: use xas_try_split() in shmem_split_large_entry() Date: Wed, 26 Feb 2025 16:08:54 -0500 Message-ID: <20250226210854.2045816-3-ziy@nvidia.com> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250226210854.2045816-1-ziy@nvidia.com> References: <20250226210854.2045816-1-ziy@nvidia.com> X-ClientProxiedBy: MN2PR14CA0016.namprd14.prod.outlook.com (2603:10b6:208:23e::21) To DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR12MB9473:EE_|SA1PR12MB7221:EE_ X-MS-Office365-Filtering-Correlation-Id: c34acc3d-dcae-4bb5-619a-08dd56a9cb0c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|7416014|1800799024|7053199007; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS7PR12MB9473.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(376014)(7416014)(1800799024)(7053199007);DIR:OUT;SFP:1101; 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Instead of splitting all n slots, only the 1 slot covered by the folio need to be split and the remaining n-1 shadow entries can be retained with orders ranging from 0 to n-1. This method only requires (n/XA_CHUNK_SHIFT) new xa_nodes instead of (n % XA_CHUNK_SHIFT) * (n/XA_CHUNK_SHIFT) new xa_nodes, compared to the original xas_split_alloc() + xas_split() one. For example, to split an order-9 large swap entry (assuming XA_CHUNK_SHIFT is 6), 1 xa_node is needed instead of 8. xas_try_split_min_order() is used to reduce the number of calls to xas_try_split() during split. Signed-off-by: Zi Yan Cc: Baolin Wang Cc: Hugh Dickins Cc: Kairui Song Cc: Mattew Wilcox Cc: Miaohe Lin Cc: David Hildenbrand Cc: John Hubbard Cc: Kefeng Wang Cc: Kirill A. Shuemov Cc: Ryan Roberts Cc: Yang Shi Cc: Yu Zhao Reviewed-by: Baolin Wang Tested-by: Baolin Wang --- mm/shmem.c | 59 ++++++++++++++++++++++++++---------------------------- 1 file changed, 28 insertions(+), 31 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index b959edf15073..f08ba9718013 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2153,15 +2153,16 @@ static int shmem_split_large_entry(struct inode *inode, pgoff_t index, { struct address_space *mapping = inode->i_mapping; XA_STATE_ORDER(xas, &mapping->i_pages, index, 0); - void *alloced_shadow = NULL; - int alloced_order = 0, i; + int split_order = 0, entry_order; + int i; /* Convert user data gfp flags to xarray node gfp flags */ gfp &= GFP_RECLAIM_MASK; for (;;) { - int order = -1, split_order = 0; void *old = NULL; + int cur_order; + pgoff_t swap_index; xas_lock_irq(&xas); old = xas_load(&xas); @@ -2170,60 +2171,56 @@ static int shmem_split_large_entry(struct inode *inode, pgoff_t index, goto unlock; } - order = xas_get_order(&xas); + entry_order = xas_get_order(&xas); - /* Swap entry may have changed before we re-acquire the lock */ - if (alloced_order && - (old != alloced_shadow || order != alloced_order)) { - xas_destroy(&xas); - alloced_order = 0; - } + if (!entry_order) + goto unlock; /* Try to split large swap entry in pagecache */ - if (order > 0) { - if (!alloced_order) { - split_order = order; + cur_order = entry_order; + swap_index = round_down(index, 1 << entry_order); + + split_order = xas_try_split_min_order(cur_order); + + while (cur_order > 0) { + pgoff_t aligned_index = + round_down(index, 1 << cur_order); + pgoff_t swap_offset = aligned_index - swap_index; + + xas_set_order(&xas, index, split_order); + xas_try_split(&xas, old, cur_order); + if (xas_error(&xas)) goto unlock; - } - xas_split(&xas, old, order); /* * Re-set the swap entry after splitting, and the swap * offset of the original large entry must be continuous. */ - for (i = 0; i < 1 << order; i++) { - pgoff_t aligned_index = round_down(index, 1 << order); + for (i = 0; i < 1 << cur_order; + i += (1 << split_order)) { swp_entry_t tmp; - tmp = swp_entry(swp_type(swap), swp_offset(swap) + i); + tmp = swp_entry(swp_type(swap), + swp_offset(swap) + swap_offset + + i); __xa_store(&mapping->i_pages, aligned_index + i, swp_to_radix_entry(tmp), 0); } + cur_order = split_order; + split_order = xas_try_split_min_order(split_order); } unlock: xas_unlock_irq(&xas); - /* split needed, alloc here and retry. */ - if (split_order) { - xas_split_alloc(&xas, old, split_order, gfp); - if (xas_error(&xas)) - goto error; - alloced_shadow = old; - alloced_order = split_order; - xas_reset(&xas); - continue; - } - if (!xas_nomem(&xas, gfp)) break; } -error: if (xas_error(&xas)) return xas_error(&xas); - return alloced_order; + return entry_order; } /*