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[103.168.172.200]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8c096783662sm67864185a.5.2025.12.18.16.43.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Dec 2025 16:43:44 -0800 (PST) Received: from phl-compute-06.internal (phl-compute-06.internal [10.202.2.46]) by mailfauth.phl.internal (Postfix) with ESMTP id BF7F9F40075; Thu, 18 Dec 2025 19:43:43 -0500 (EST) Received: from phl-frontend-03 ([10.202.2.162]) by phl-compute-06.internal (MEProxy); Thu, 18 Dec 2025 19:43:43 -0500 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeefgedrtddtgdegieeklecutefuodetggdotefrod ftvfcurfhrohhfihhlvgemucfhrghsthforghilhdpuffrtefokffrpgfnqfghnecuuegr ihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjug hrpeffhffvvefukfhfgggtuggjsehttdertddttddvnecuhfhrohhmpeeuohhquhhnucfh vghnghcuoegsohhquhhnrdhfvghnghesghhmrghilhdrtghomheqnecuggftrfgrthhtvg hrnhephedugfduffffteeutddvheeuveelvdfhleelieevtdeguefhgeeuveeiudffiedv necuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomhepsghoqh hunhdomhgvshhmthhprghuthhhphgvrhhsohhnrghlihhthidqieelvdeghedtieegqddu jeejkeehheehvddqsghoqhhunhdrfhgvnhhgpeepghhmrghilhdrtghomhesfhhigihmvg drnhgrmhgvpdhnsggprhgtphhtthhopeeffedpmhhouggvpehsmhhtphhouhhtpdhrtghp thhtohepmhgrthhhihgvuhdruggvshhnohihvghrshesvghffhhitghiohhsrdgtohhmpd hrtghpthhtohepjhhovghlsehjohgvlhhfvghrnhgrnhguvghsrdhorhhgpdhrtghpthht ohepphgruhhlmhgtkheskhgvrhhnvghlrdhorhhgpdhrtghpthhtoheplhhinhhugidqkh gvrhhnvghlsehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtohepnhhpihhgghhi nhesghhmrghilhdrtghomhdprhgtphhtthhopehmphgvsegvlhhlvghrmhgrnhdrihgurd gruhdprhgtphhtthhopehgrhgvghhkhheslhhinhhugihfohhunhgurghtihhonhdrohhr ghdprhgtphhtthhopegsihhgvggrshihsehlihhnuhhtrhhonhhigidruggvpdhrtghpth htohepfihilhhlsehkvghrnhgvlhdrohhrgh X-ME-Proxy: Feedback-ID: iad51458e:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Thu, 18 Dec 2025 19:43:42 -0500 (EST) Date: Fri, 19 Dec 2025 09:43:39 +0900 From: Boqun Feng To: Mathieu Desnoyers Cc: Joel Fernandes , "Paul E. McKenney" , linux-kernel@vger.kernel.org, Nicholas Piggin , Michael Ellerman , Greg Kroah-Hartman , Sebastian Andrzej Siewior , Will Deacon , Peter Zijlstra , Alan Stern , John Stultz , Neeraj Upadhyay , Linus Torvalds , Andrew Morton , Frederic Weisbecker , Josh Triplett , Uladzislau Rezki , Steven Rostedt , Lai Jiangshan , Zqiang , Ingo Molnar , Waiman Long , Mark Rutland , Thomas Gleixner , Vlastimil Babka , maged.michael@gmail.com, Mateusz Guzik , Jonas Oberhauser , rcu@vger.kernel.org, linux-mm@kvack.org, lkmm@lists.linux.dev Subject: Re: [RFC PATCH v4 3/4] hazptr: Implement Hazard Pointers Message-ID: References: <20251218014531.3793471-1-mathieu.desnoyers@efficios.com> <20251218014531.3793471-4-mathieu.desnoyers@efficios.com> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Dec 18, 2025 at 12:35:18PM -0500, Mathieu Desnoyers wrote: [...] > > Could you utilize this[1] to see a > > comparison of the reader-side performance against RCU/SRCU? > > Good point ! Let's see. > > On a AMD 2x EPYC 9654 96-Core Processor with 192 cores, > hyperthreading disabled, > CONFIG_PREEMPT=y, > CONFIG_PREEMPT_RCU=y, > CONFIG_PREEMPT_HAZPTR=y. > > scale_type ns > ----------------------- > hazptr-smp-mb 13.1 <- this implementation > hazptr-barrier 11.5 <- replace smp_mb() on acquire with barrier(), requires IPIs on synchronize. > hazptr-smp-mb-hlist 12.7 <- replace per-task hp context and per-cpu overflow lists by hlist. > rcu 17.0 Hmm.. now looking back, how is it possible that hazptr is faster than RCU on the reader-side? Because a grace period was happening and triggered rcu_read_unlock_special()? This is actualy more interesting. Regards, Boqun > srcu 20.0 > srcu-fast 1.5 > rcu-tasks 0.0 > rcu-trace 1.7 > refcnt 1148.0 > rwlock 1190.0 > rwsem 4199.3 > lock 41070.6 > lock-irq 46176.3 > acqrel 1.1 > > So only srcu-fast, rcu-tasks, rcu-trace and a plain acqrel > appear to beat hazptr read-side performance. > > [...] > [...]