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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Shuah Khan , Randy Dunlap , Brendan Jackman , Johannes Weiner , linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 0/8] mm/page_owner: Add PID/TGID/COMM and cgroup filtering Date: Wed, 09 Sep 2026 11:54:51 -0400 X-Mailer: MailMate (3.0r7028) Message-ID: <22D1EC4B-FBCB-421E-B8DA-345B5F3505FB@nvidia.com> In-Reply-To: References: <20260907082620.2083838-1-zhen.ni@easystack.cn> <79548641-25f3-4ec3-a549-782fad168962@kernel.org> <6e8bfb0d-d595-4e6b-9536-0323ada57e25@easystack.cn> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-MS-Reactions: disallow X-ClientProxiedBy: BLAP220CA0012.NAMP220.PROD.OUTLOOK.COM (2603:10b6:208:32c::17) To IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: IA0PR12MB8374:EE_|SJ2PR12MB9140:EE_ X-MS-Office365-Filtering-Correlation-Id: 33f6e43f-0234-4e76-b05d-08df0e8ab1ea X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|23010399003|376014|7416014|1800799024|4143699003|11063799006|10067099003|56012099006|22082099003|18002099003|6133799003|3023799007; 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Following the previous series that introduced print_mode and >>>> NUMA node filters: >>>>    https://lore.kernel.org/linux-mm/20260707115411.1714314-1- >>>> zhen.ni@easystack.cn/ >>>> >>>> This series adds filtering capabilities to page_owner, allowing users to >>>> filter output by specific processes and memory cgroups. Users can now >>>> filter page_owner output by PID, TGID, COMM (with wildcard support), and >>>> memory cgroup path. This makes page_owner debugging more focused and >>>> efficient for tracking memory allocations in specific contexts. >>>> >>>> Targeted filtering provides significant performance benefits on large memory >>>> servers by reducing both execution time and output size. By filtering at the >>>> kernel level before reading, only relevant page allocations are processed, >>>> dramatically reducing the amount of data that needs to be handled in userspace. >>> >>> page_owner is used for debugging. Why do we have to add kernel code to make it >>> faster? >>> >>> How much faster are we talking about? >> >> On my VM with just 2GB of RAM, the raw page_owner output takes real >> 0m6.178s. Filter it down to PID 1, and it drops to real 0m0.286s. Handle >> mode takes real 0m0.938s — roughly an 85% speedup. I've also tried this >> on a 1TB server, and it's very slow. The numbers would look even more >> extreme. >> >> You're right that execution time isn't the main concern for a debug >> tool. But that's kind of the point — I'm trying to optimize the current >> execution flow of page_owner, reduce unnecessary overhead, and make the >> tool more user-friendly (especially for servers with 1TB+ of memory).If >> the user only cares about a specific slice of memory, why dump >> everything from the kernel side and then filter it all over again in >> userspace? Might as well filter at the source. > > Because it results in less kernel code :) > > And less kernel code is good. Unless unavoidable. An alternative is to add BPF hooks like bpf_iter to do the filtering and by default, when no BPF program is attached, everything is printed. Best Regards, Yan, Zi