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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Brendan Jackman , Johannes Weiner , Zi Yan , Oscar Salvador , Qi Zheng , Shakeel Butt , Axel Rasmussen , Yuanchu Xie , Wei Xu References: <06b2a2b6-d5c8-4522-8e22-10616f887846@amd.com> Content-Language: en-US From: "Cheatham, Benjamin" In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: satlexmb08.amd.com (10.181.42.217) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN1PEPF00026368:EE_|CH3PR12MB8972:EE_ X-MS-Office365-Filtering-Correlation-Id: 0a21cfff-da7d-4d91-0965-08de72ff7980 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|1800799024|36860700013|82310400026|13003099007|7053199007; X-Microsoft-Antispam-Message-Info: =?utf-8?B?NXZBNGRnNGp2c2haaHZlTGNEcWU0cDBFTzcxNFR6bmhWZjVEOG9hNXhUMmxN?= =?utf-8?B?SWNOMDlTOXBCSWVKaFZPelRzdUJ5RlRLQWNpaXYrbVBaamJ2eXQxb0lWcS9L?= =?utf-8?B?RzA3VjFDMW5uYVdtWVZ3VkFOV1NheWJaUG5CQko1c0gyUlRLYjl3WHBrSSt3?= =?utf-8?B?WTRpZFdjN1lxVWVOMEg0OTRtaWpocVMzclh3K2trSWRHVEE1YlE5WDhDdzdx?= =?utf-8?B?bG9WbUZWWDg2WHRWZTVKZGRTUmU5S3VYb1J1RlJEZXh3T3BMcHpxejlHeVZx?= =?utf-8?B?ZWRUQzFYbWs5ejhIUEZzdGcyZE5PVlVGZE5NTUZpK25NYWVuODZtMFlWMy8y?= =?utf-8?B?bEh1aXBVNjgvMGlUL3pBc2txMlMxSG91NWV2Y1VKVldxa3YvS011ODluckxw?= =?utf-8?B?R0t2UTBqVmdUSE5jOEVMZngyZEpxRW1nTnFFTlZ2Nm90ekRUdURSRkozK2gy?= =?utf-8?B?bzdrRUlUajhsdmlTRmkxV0Z1WXRTdGRaRUNrUE0xclpuNmVXaWNYRHNoY2hn?= =?utf-8?B?Q1FGbkFuejdFZEJiZFYvaENvRVdxdWVpVXNreE9xRVhONXFmL2dIZmwyTDFj?= =?utf-8?B?U3JVQ01BSXF2NnVQdUZnKzA3Yjlna0FSUlQ2aTgyZGJBVVRrQnVHYityTnZI?= =?utf-8?B?ZXVBdGR4RUdFNkRmcjhuQVFiOUpLN0ZINVNBZVdFV0pMZE5ZL05oQXBxaTh4?= =?utf-8?B?b1JSeXVoSUc5NHp5WWVvampLQ0JHa1BzVDhXT1ZCSGg3a280UTZ3NUtkVzVt?= =?utf-8?B?WWtoYXpqd1I0KzI5WXVveGNLL0pldWtDODBDTFJVaGRBcndxZiszYzQ2UkFF?= =?utf-8?B?WmRmRGNJamFBeGU4VkU5SlBFT1cxclNVbDlZMjNIUHdINzh1VUcyUG9DcWRO?= =?utf-8?B?UTl4RGZTVHNJQ2xITGFGSG1ZMXVnUE9NMUs0YTgxcG1HZjBCSlhmaVhsbTQ2?= =?utf-8?B?U29mc0V4dlY1cWMvUVVSQ0NtaVpqdnVRUnFLSExET0t3Nm9rcTZBRytReDJE?= =?utf-8?B?dVRWVXU3ay91cnZrbElQZ1JuWStYOGlwdGgwcWgrZzVOSDlxZ2RTeVh1d2Zp?= =?utf-8?B?ZXVYblJJcnFLbmtGYWZEZUFGZHpTTWIwcytJS1QvVEp6UDlpQmpST0ZBb083?= =?utf-8?B?S0FCQ0Y5ZjhCbjV5ZVRrT1dOZHE2dTljeDYxc2FkbHNzcS81bUhMSEQ4ZUxn?= =?utf-8?B?NGZ6aC9ZSEJjOE1uOUlRZFdaK3JhdlFMYmtNZ1UzWXpIQVNzMUFGRWI4R3hM?= =?utf-8?B?UnF6Q1dxTUhNa0NqdEhxaXQxbWY5d3ByM3ZxdG5FSG9BQVNnYkoybFdOL05J?= =?utf-8?B?bjJVaTh2TmJHamxOeEFleVBNRUc1bzNrMjFCckJENVhGSFVBYzVqRlZkYlFT?= =?utf-8?B?WUFZbVZpRFJpSVBGM1pncVByUUNGeWdZUmhGRitJRGpPV0EyRDQ2azhMbFRW?= =?utf-8?B?cjVyN3hHNFBOelh1MEM4Ti9GODI5OGZBL0w1ZE5zc3UxdXNGdDFIZE4xd1g0?= =?utf-8?B?WHRPQmNDd0d4NGthUlpYY0dzNGdoTGd1bVIyeGV0WlhMaktTSHBhampPWE4w?= =?utf-8?B?a0Y1QWNQbWZ5eVIwYVRob2E3ZzluUjFSaWpDSmlsWDhSUWxWVXhGQzVQT3FU?= =?utf-8?B?OEVVMVJuSk1PNGVBcHRSSlNDQnMzRmZqcVRoQWtoU0I2WGRiUklXa1NxQmN1?= =?utf-8?B?Vkp6dnFXZ0lrM1YxOC8rSnUyWTdpNmpkU0JHVzE3S21HQlJTTERWUEEzZWNi?= =?utf-8?B?SlJ1dDVMTnpsK3ZRaWVTcEsxWkFZZktTY2RmSFp2dS9sZXBxemNtcm93Z1F4?= =?utf-8?B?ekttbjRISk1UM2ZFUk9nZUZzanN2ekg2bnN6QnVBVHVnQ3Nuc2VjMXlBbFZT?= =?utf-8?B?Y2pyZ3hzOHZJNG5ibHgwR05HVmVta0hpd3JnQkFLT3NMMU9SZFhROU9QeVV2?= =?utf-8?B?MG1pQ240Rjl1QXZkTEQ5SmhYYlg1eHJYVW12aklnY3JvNWFNazROUW44Z2pG?= =?utf-8?B?andxTnM0cWg2VFJzT0FCUCt4U0FtdWZ2SWpzYXQ5TCs1QzA3R1ZWZ3h0elRU?= =?utf-8?B?U0lhK3FuM3R3Tm9CWENXRzN0d0hJbW9oWXVJejVWMWNHVWRhenVuZTg3c2FP?= =?utf-8?B?L2trRHNLbUhxOTVncFFHTWIzVUhSdXFxVkcwUTExWDJwenBubnFqSmU2YXBT?= =?utf-8?B?UlVvY0lESlJJVXcyaVVYUlJuWGxVQlhqangzUDA5MjlXTTFWTTJmUkxUQVZt?= =?utf-8?B?TGlLbXNuaXVWS3dzRCtCMm9HTHJRPT0=?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(7416014)(376014)(1800799024)(36860700013)(82310400026)(13003099007)(7053199007);DIR:OUT;SFP:1101; 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Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ] > > On Fri, Feb 20, 2026 at 01:09:59PM -0600, Cheatham, Benjamin wrote: >> On 2/11/2026 9:22 AM, Dmitry Ilvokhin wrote: >>> Zone lock contention can significantly impact allocation and >>> reclaim latency, as it is a central synchronization point in >>> the page allocator and reclaim paths. Improved visibility into >>> its behavior is therefore important for diagnosing performance >>> issues in memory-intensive workloads. >>> >>> On some production workloads at Meta, we have observed noticeable >>> zone lock contention. Deeper analysis of lock holders and waiters >>> is currently difficult with existing instrumentation. >>> >>> While generic lock contention_begin/contention_end tracepoints >>> cover the slow path, they do not provide sufficient visibility >>> into lock hold times. In particular, the lack of a release-side >>> event makes it difficult to identify long lock holders and >>> correlate them with waiters. As a result, distinguishing between >>> short bursts of contention and pathological long hold times >>> requires additional instrumentation. >>> >>> This patch series adds dedicated tracepoint instrumentation to >>> zone lock, following the existing mmap_lock tracing model. >>> >>> The goal is to enable detailed holder/waiter analysis and lock >>> hold time measurements without affecting the fast path when >>> tracing is disabled. >>> >>> The series is structured as follows: >>> >>> 1. Introduce zone lock wrappers. >>> 2. Mechanically convert zone lock users to the wrappers. >>> 3. Convert compaction to use the wrappers (requires minor >>> restructuring of compact_lock_irqsave()). >>> 4. Add zone lock tracepoints. >> >> I think you can improve the flow of this series if reorder as follows: >> 1. Introduce zone lock wrappers >> 4. Add zone lock tracepoints >> 2. Mechanically convert zone lock users to the wrappers >> 3. Convert compaction to use the wrappers... >> >> and possibly squash 1 & 4 (though that might be too big of a patch). It's better to introduce the >> wrappers and their tracepoints together before the reviewer (i.e. me) forgets what was added in >> patch 1 by the time they get to patch 4. > > Hi Ben, > > Thanks for the suggestion. > > I structured the series intentionally to keep all behavior-preserving > refactoring separate from the actual instrumentation change. > > In particular, I had to split the conversion into two patches to > separate the purely mechanical changes from the compaction > restructuring. With the current order, tracepoints addition remains a > single, atomic functional change on top of a fully converted tree. This > keeps the instrumentation isolated from the refactoring and with an > intention to make bisection and review of the behavioral change easier. > > Reordering as suggested would mix instrumentation with intermediate > refactoring states, which I'd prefer to avoid. > > I hope this reasoning makes sense, but I'm happy to discuss if there are > strong objections. No that's fine, I figured as much. I just wasn't sure that was more important to you than what (I thought) was a better reading order for the series. Thanks, Ben > >> >> Thanks, >> Ben