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Howlett" To: Andrew Morton Cc: maple-tree@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Paul E . McKenney" , Suren Baghdasaryan , Matthew Wilcox , "Liam R. Howlett" Subject: [PATCH 0/6] maple_tree: Change replacement strategy Date: Fri, 4 Aug 2023 12:59:45 -0400 Message-Id: <20230804165951.2661157-1-Liam.Howlett@oracle.com> X-Mailer: git-send-email 2.39.2 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: YT4PR01CA0181.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:110::8) To SN6PR10MB3022.namprd10.prod.outlook.com (2603:10b6:805:d8::25) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN6PR10MB3022:EE_|PH0PR10MB4469:EE_ X-MS-Office365-Filtering-Correlation-Id: 26ad192b-fcb6-41fa-21d1-08db950c43ea X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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:SN6PR10MB3022.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230028)(376002)(366004)(39860400002)(396003)(346002)(136003)(1800799003)(186006)(451199021)(41300700001)(8936002)(8676002)(83380400001)(26005)(6506007)(107886003)(86362001)(38100700002)(2616005)(1076003)(316002)(6666004)(4326008)(6512007)(6486002)(478600001)(54906003)(6916009)(36756003)(2906002)(66476007)(5660300002)(66946007)(66556008);DIR:OUT;SFP:1101; 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This could be problematic when used in the RCU context since the writer may be starved of CPU time by the readers. This patch set addresses the issue by switching the data replacement strategy to one that will only mark data as dead once the new data is available. This series changes the ordering of the node replacement so that the new data is live before the old data is marked 'dead'. When readers hit 'dead' nodes, they will restart from the top of the tree and end up in the new data. In more complex scenarios, the replacement strategy means a subtree is built and graphed into the tree leaving some nodes to point to the old parent. The view of tasks into the old data will either remain with the old data, or see the new data once the old data is marked 'dead'. Iterators will see the 'dead' node and restart on their own and switch to the new data. There is no risk of the reader seeing old data in these cases. The 'dead' subtree of data is then fully marked dead, but reused nodes will still point to the dead nodes until the parent pointer is updated. Walking up to a 'dead' node will cause a re-walk from the top of the tree and enter the new data area where old data is not reachable. Once the parent pointers are fully up to date in the active data, the 'dead' subtree is iterated to collect entirely 'dead' subtrees, and dead nodes (nodes that partially contained reused data). Liam R. Howlett (6): maple_tree: Add hex output to maple_arange64 dump maple_tree: Reorder replacement of nodes to avoid live lock maple_tree: introduce mas_put_in_tree() maple_tree: Introduce mas_tree_parent() definition maple_tree: Change mas_adopt_children() parent usage maple_tree: Replace data before marking dead in split and spanning store lib/maple_tree.c | 607 +++++++++++++++++++---------------------------- 1 file changed, 240 insertions(+), 367 deletions(-) -- 2.39.2