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McKenney" , rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Boqun Feng , Steven Rostedt , lkmm@lists.linux.dev, Zqiang , Wang Lian , Kunwu Chan , Nicholas Piggin , Michael Ellerman , Greg Kroah-Hartman , Sebastian Andrzej Siewior , Will Deacon , Peter Zijlstra , Alan Stern , John Stultz , Andrew Morton , Frederic Weisbecker , Joel Fernandes , Josh Triplett , Uladzislau Rezki , Lai Jiangshan , Zqiang , Ingo Molnar , Waiman Long , Mark Rutland , Thomas Gleixner , Vlastimil Babka , maged.michael@gmail.com, Mateusz Guzik , Jonas Oberhauser , linux-mm@kvack.org References: <20260919000056.3132131-1-paulmck@kernel.org> <6B1FC39D-6EB0-433A-8E49-E5EFC9379AD7@mainlining.org> From: Mathieu Desnoyers Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: YQ1P288CA0018.CANP288.PROD.OUTLOOK.COM (2603:10b6:c01:9e::20) To YT6PR01MB491026.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:1d0::10) 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=?utf-8?Q?/d/HmAXJ4Xw2nqKxPVOC7UMzAb0MFqG2fXziAYztphPPI?= X-MS-Exchange-AntiSpam-MessageData-1: tB8FxsHLmMLZbnkcfV1QniRB93nQCG66PZk= X-OriginatorOrg: efficios.com X-MS-Exchange-CrossTenant-Network-Message-Id: c841ca50-54df-48f8-5fd8-08df1670bd88 X-MS-Exchange-CrossTenant-AuthSource: YT6PR01MB491026.CANPRD01.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Sep 2026 17:09:18.2694 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4f278736-4ab6-415c-957e-1f55336bd31e X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: dr/nN3WCr/Z8a6Ei4Pw5hhC4q82GMQ7xb7iep8wLe9KlO5MQcekl+5FknimJ88lzeEAW+SR9mZJX+KnVFEqEafpadmmoyBsHUFATv7AsWvY= X-MS-Exchange-Transport-CrossTenantHeadersStamped: YT5PR01MB324718 On 2026-09-19 13:00, Linus Torvalds wrote: > On Sat, 19 Sept 2026 at 09:35, Bradley Morgan wrote: >> >> I think hazard pointers are good, what test do YOU suggest we do here? > > I want to see a single real-world example of "look, this speeds this > real load up by 10%, and the kernel code was actually cleaned up in > the process because hazard pointers are great". > > Not a microbenchmark that tests just the hazard pointers themselves, > but a real kernel feature that has been converted to hazard pointers, > and in the process actually shows improvement. > > The ONLY reason for hazard pointers to ever be merged is if they > actually buy us something real. > > So I want to see that 'real" thing. AFAIR, Boqun wanted to use hazard pointers to cleanup/speed up an hot lockdep reclaim path. Boqun, Paul, how is this effort going ? I suspect we should wait until that lockdep user of hazptr is ready for upstreaming and propose both at the same time, because a synchronization infrastructure without any significant in tree user is not really relevant, right ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com