From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7C18B6EB74 for ; Fri, 12 Jan 2024 14:52:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="0Tb4v22A"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="5zjTs2Ta" From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1705071154; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=NdU9EUuaq5xIuz7Dx7kAj78GZgJNR892u+3NLj09xAU=; b=0Tb4v22AWgQyxnaapyqWuR7ryqLwix39lSCDgP0LIcnQp3fDK53xfz6AWo7GZp/Bwb366w JkmW3kCaIgFHZQ5WXQOkLckLiRTF/BV0ybqrXtH5Fo0LoSugWJZ9c7G4mtDwBM5/mX/hbC xHRaY1ZupKxAD+GNACdouJnrPckgqEbsT9eY6JAXlGzaeNvL7f9JrW6vyQD5hgDWhN9F0Y KLjqHC55G/HC0aeqfiifLULB7DmdbFrX2o3QYvpCZ4CEpsNVxcYPvMs7ca6Ui7fjSh8Ggc 9RPw+kVkj8Z3VPInEPXNf9Lc1XIHcmJf6VuS++D/W2R1U5GFpIPzP603W6Wc4w== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1705071154; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=NdU9EUuaq5xIuz7Dx7kAj78GZgJNR892u+3NLj09xAU=; b=5zjTs2TaDiewcCXytz4MwOSffHfvhZPS44D/4UVseXR1sk4VLjrwDpJRJjrNcOVOoPm34H MFr5TBHTzJ3Vh5Cw== To: Pierre Gondois , Anna-Maria Behnsen , linux-kernel@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider Subject: Re: [PATCH] sched/idle: Prevent stopping the tick when there is no cpuidle driver In-Reply-To: References: <20231215130501.24542-1-anna-maria@linutronix.de> <87ttnmiif9.fsf@somnus> <06a2561f-557b-4eaa-8f11-75883bbbaef9@arm.com> <87a5pag6q7.fsf@somnus> Date: Fri, 12 Jan 2024 15:52:33 +0100 Message-ID: <87mstaioy6.ffs@tglx> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Fri, Jan 12 2024 at 14:39, Pierre Gondois wrote: > On 1/12/24 11:56, Anna-Maria Behnsen wrote: >> Pierre Gondois writes: >>> I agree that the absence of cpuidle driver prevents from reaching deep >>> idle states. FWIU, there is however still benefits in stopping the tick >>> on such platform. >> >> What's the benefit? > > I did the following test: > - on an arm64 Juno-r2 platform (2 big A-72 and 4 little A-53 CPUs) > - booting with 'cpuidle.off=1' > - using the energy counters of the platforms > (the counters measure energy for the whole cluster of big/little CPUs) > - letting the platform idling during 10s > > So the energy consumption would be up: > - ~6% for the big CPUs > - ~10% for the litte CPUs Fair enough, but what's the actual usecase? NOHZ w/o cpuidle driver seems a rather academic exercise to me. Thanks, tglx