From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 5B2BE1FC7F8 for ; Sun, 23 Feb 2025 10:00:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740304837; cv=none; b=Wtu5caxrvCJmZyBgx3IorPueRSpiO4wU+tujCypL9T/rTZ3akEnStqHZEfM6H8B1Yq//xzYaUcsZ41VTCxmOc8Il/0hMTxS0h71aRuxTP8g46S2wXJfMkIRSJxd9hfKpgKqMI86yTe2aBJo/ViivX60X2IF7vZVtrH17DXmvalM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740304837; c=relaxed/simple; bh=pmcHYHCiNgsF3nHoAFCcHPhsEZjhrg+MxkpBr1R1+NY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=isAB3cjVXl9Zu3rM0UJDxdOfw1d5XfCwrkRYYcnbowV5H+GVUwaUz0VPmC5Jz8b+63Q5RzW2Bdyqem7/y7HB5eyXgjj9d+EU0CHUmUvmVvpyZo7ApfdQgVihbSdxIEt/WOtTSQicwlACMch1Vq5UedbHzYy/PJAPrms8RbnyO3Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=N+MF4zLJ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="N+MF4zLJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 79A1AC4CEDD; Sun, 23 Feb 2025 10:00:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1740304836; bh=pmcHYHCiNgsF3nHoAFCcHPhsEZjhrg+MxkpBr1R1+NY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=N+MF4zLJ24fBk4xLtjB7/tA6boqFKtcLqL/am6lrHygi3nHeBTwU5SWMkJSTj6Vd0 UTsWnUpe1nDES2SKqIeDmfjn3E1E6FueOIL1Yd2wcdrQzw0N6V/+SBpOLCKz6M3N9R rkme7Q41U7t2jdJ8nKehvnAMG3vGb4YK0zy4YL8QhpWYL6a8drxWeYpwFUcmWvEAIY EWsTIQjTY34fiDALkKSZBjawlfI1IHWliw3VbQCnLroCWPVg9pXg4Nv9VBs+P6srXO Jy2Pk1NJNn5ZHrCbCxjDwrrdnfsBRQsKr+gpipH9iRyeYjrwvruJts7YZTzD9ESbX3 sIaEwx/tUrHNw== Date: Sun, 23 Feb 2025 11:00:26 +0100 From: Ingo Molnar To: Andrea Righi Cc: Joel Fernandes , Qais Yousef , Thomas Gleixner , Peter Zijlstra , Vincent Guittot , Juri Lelli , Steven Rostedt , John Stultz , Saravana Kannan , Dietmar Eggemann , Frederic Weisbecker , linux-kernel@vger.kernel.org, Linus Torvalds , Andrew Morton Subject: Re: [PATCH] Kconfig.hz: Change default HZ to 1000 Message-ID: References: <20250210001915.123424-1-qyousef@layalina.io> <20250212145054.GA1965539@joelnvbox> 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=us-ascii Content-Disposition: inline In-Reply-To: * Andrea Righi wrote: > On Wed, Feb 12, 2025 at 09:50:54AM -0500, Joel Fernandes wrote: > > On Mon, Feb 10, 2025 at 12:19:15AM +0000, Qais Yousef wrote: > ... > > > I believe HZ_250 was the default as a trade-off for battery power > > > devices that might not be happy with frequent TICKS potentially draining > > > the battery unnecessarily. But to my understanding the current state of > > > > Actually, on x86, me and Steve did some debug on Chromebooks and we found > > that HZ_250 actually increased power versus higher HZ. This was because > > cpuidle governor changes C states on the tick, and by making it less > > frequent, the CPU could be in a shallow C state for longer. > > FWIW, I found the same about power consumption when we decided to switch to > CONFIG_HZ=1000 in the Ubuntu kernel: > https://discourse.ubuntu.com/t/enable-low-latency-features-in-the-generic-ubuntu-kernel-for-24-04/42255 The "HZ=1000 reduces power consumption or keeps it the same" is actually a pretty good argument to change the default to HZ=1000. These experiments and numbers (if any) should be incorporated in the changelog prominently - as actual data and the Kconfig decisions made by major distros will, most of the time, be superior to meta analysis that seems to be the changelog right now. Thanks, Ingo