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[90.233.217.52]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-54d3d5104c6sm1695748e87.195.2025.04.16.08.04.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Apr 2025 08:04:34 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Wed, 16 Apr 2025 17:04:31 +0200 To: Breno Leitao Cc: Boqun Feng , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , aeh@meta.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, edumazet@google.com, jhs@mojatatu.com, kernel-team@meta.com, Erik Lundgren , "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Uladzislau Rezki , rcu@vger.kernel.org Subject: Re: [RFC PATCH 0/8] Introduce simple hazard pointers for lockdep Message-ID: References: <20250414060055.341516-1-boqun.feng@gmail.com> Precedence: bulk X-Mailing-List: netdev@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 Wed, Apr 16, 2025 at 07:14:04AM -0700, Breno Leitao wrote: > Hi Boqun, > > On Sun, Apr 13, 2025 at 11:00:47PM -0700, Boqun Feng wrote: > > > Overall it looks promising to me, but I would like to see how it > > performs in the environment of Breno. Also as Paul always reminds me: > > buggy code usually run faster, so please take a look in case I'm missing > > something ;-) Thanks! > > Thanks for the patchset. I've confirmed that the wins are large on my > environment, but, at the same magnitute of synchronize_rcu_expedited(). > > Here are the numbers I got: > > 6.15-rc1 (upstream) > # time /usr/sbin/tc qdisc replace dev eth0 root handle 0x1234: mq > real 0m3.986s > user 0m0.001s > sys 0m0.093s > > Your patchset on top of 6.15-rc1 > # time /usr/sbin/tc qdisc replace dev eth0 root handle 0x1234: mq > real 0m0.072s > user 0m0.001s > sys 0m0.070s > > > My original proposal of using synchronize_rcu_expedited()[1] > # time /usr/sbin/tc qdisc replace dev eth0 root handle 0x1234: mq > real 0m0.074s > user 0m0.001s > sys 0m0.061s > > Link: https://lore.kernel.org/all/20250321-lockdep-v1-1-78b732d195fb@debian.org/ [1] > Could you please also do the test of fist scenario with a regular synchronize_rcu() but switch to its faster variant: echo 1 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp and run the test. If you have a time. Thank you! -- Vlad Rezki