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[79.51.63.186]) by smtp.gmail.com with ESMTPSA id tj2-20020a170907c24200b00a3da0cecc10sm133112ejc.118.2024.02.14.23.51.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Feb 2024 23:51:55 -0800 (PST) Date: Thu, 15 Feb 2024 08:51:54 +0100 From: Andrea Righi To: "Paul E. McKenney" Cc: Uladzislau Rezki , Joel Fernandes , Joel Fernandes , rcu@vger.kernel.org, "Cc: Frederic Weisbecker" Subject: Re: Observation on NOHZ_FULL Message-ID: References: <6a2b6857-57e7-4321-adae-132ba69a4fff@paulmck-laptop> <0e15e91e-da47-45dd-b7de-7f89b7b6002b@joelfernandes.org> <92cba6df-01de-4daa-a0cb-5fa92c7374dd@paulmck-laptop> 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: <92cba6df-01de-4daa-a0cb-5fa92c7374dd@paulmck-laptop> On Tue, Feb 06, 2024 at 10:44:33AM -0800, Paul E. McKenney wrote: ... > > > > - with lazy RCU enabled hrtimer_interrupt() takes like 2x more to > > return, respect to the other cases (is this expected?) > > This last is surprising at first glance, but I could be missing > something. Joel, Uladzislau, thoughts? On this specific point, I repeated the tests with the latest 6.8 kernel and now I don't notice this difference anymore. hrtimer_interrupt() time is always in the range [4K, 16K) ns, both with lazy RCU off and lazy RCU on. I don't really know why I was getting different results, probably some noise triggered by something running in user-space...? In any case I will update my old post with these new results and I wouldn't consider this an issue for now. Thanks, -Andrea