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[109.154.33.115]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4391da965b3sm133163775e9.5.2025.02.09.17.14.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 09 Feb 2025 17:14:14 -0800 (PST) Date: Mon, 10 Feb 2025 01:14:13 +0000 From: Qais Yousef To: Peter Zijlstra Cc: Thomas Gleixner , John Stultz , LKML , Anna-Maria Behnsen , Frederic Weisbecker , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Stephen Boyd , Yury Norov , Bitao Hu , Andrew Morton , kernel-team@android.com Subject: Re: [RFC][PATCH 0/3] DynamicHZ: Configuring the timer tick rate at boot time Message-ID: <20250210011413.whnkxo4modrx6gbc@airbuntu> References: <20250128063301.3879317-1-jstultz@google.com> <87cyg67up9.ffs@tglx> <20250203111433.GF7145@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250203111433.GF7145@noisy.programming.kicks-ass.net> On 02/03/25 12:14, Peter Zijlstra wrote: > The whole preemption thing could probably be replaced with HRTICK (which > might be suffering from bitrot), but the problem has always been with > hrtimers being too expensive (on x86). But ideally we'd move away from > tick based preemption. I do think HRTICK must be on by default. Precise time slices are important. Especially if your plans to attach changing of base_slice to sched_attr->runtime are still happening. People will find lots of surprises when they ask for 500us runtime but end up running (much) longer, especially with the default 4ms TICK value (which I just posted a patch to change it). Can we re-evaluate the HRTICK impact?