From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 8225A25BEE5; Tue, 14 Oct 2025 14:18:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760451508; cv=none; b=FMxXUbUUL2xtOPPeIZvif8yPVjbdYtJ9gBdKslDwIsfktaO/tO2qDbT6K5ZH5Sl6pnFl35TQxAwrGMw5TCLzJWplCNZCJ/pwqukaw+kAtQkUMhweRpXYV4OV3iKHnsGYAckoff59x0JONv0Zs5QiWmy96Wub5HOxjqujuuEm3LM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760451508; c=relaxed/simple; bh=C6uXU8IHXxoZXH1bAxIf/BeNm0rAdsdg75UMFU/czVY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=IjAD6B95dNuKb7/b5wrrdu5tUs28p8GNYqGE5+6t/koG5obw8D6dswBFwqM/lJPyfb5Uwqp1NVE0xYMIpsXMszhuLIuhkr4BLPpNSI2XFNyoDhNhR4yacdWlDYuPNuFgMEyJNPszBvRPXve+jRZkcOJfjV3vAXLMJt20WNae528= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=g5FGoCuL; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="g5FGoCuL" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=iioJ+H5BgqY5puHAxyGpj4x0tQd8UQglUZLFQMVFr44=; b=g5FGoCuL0zimjyfsecg0GRPO3s f2hG87ySsnZH7QcTJb8TQCsEySz2dFP4keEkjH5kzFbd/KkjPxKdkXKEqEgtiGQ/Te5cxe+Y2+U6q /kOztLe5ogwbAvF91sF91iGZ2+mhRuA9BvvcmGjV8tMX09UwRpVdrMRetqlORBFBDfwu6ARcRLyKB scfsGWlt02Rr+PxFo2fszdISCCzl85Uycsc6IGprodh3E6yMvAGJ7AnRqpu3mc4Ac7qB6Rzo7mKqX bpAxQFCB24P7lkEa7Xa8AlRgLQUB5A8ksAjQoI0GntfG9rsTpx7akpNBe1/RxrfDxJ89jH/XEW23m N8TRJhfA==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1v8fqF-00000005ErK-3Loc; Tue, 14 Oct 2025 14:17:32 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id C2CF4300212; Tue, 14 Oct 2025 16:17:30 +0200 (CEST) Date: Tue, 14 Oct 2025 16:17:30 +0200 From: Peter Zijlstra To: Geert Uytterhoeven Cc: Christophe Leroy , K Prateek Nayak , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Juri Lelli , Vincent Guittot , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , thomas.weissschuh@linutronix.de, Li Chen , Bibo Mao , Mete Durlu , Tobias Huschle , Easwar Hariharan , Guo Weikang , "Rafael J. Wysocki" , Brian Gerst , Patryk Wlazlyn , Swapnil Sapkal , "Yury Norov [NVIDIA]" , Sudeep Holla , Jonathan Cameron , Andrea Righi , Yicong Yang , Ricardo Neri , Tim Chen , Vinicius Costa Gomes Subject: Re: [PATCH v7 4/8] powerpc/smp: Introduce CONFIG_SCHED_MC to guard MC scheduling bits Message-ID: <20251014141730.GZ3245006@noisy.programming.kicks-ass.net> References: <20250826041319.1284-1-kprateek.nayak@amd.com> <20250826041319.1284-5-kprateek.nayak@amd.com> <609a980b-cbe3-442b-a492-91722870b156@csgroup.eu> <20250826080706.GC3245006@noisy.programming.kicks-ass.net> <20250826094358.GG3245006@noisy.programming.kicks-ass.net> <20251014094210.GQ3245006@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-s390@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 Tue, Oct 14, 2025 at 02:37:11PM +0200, Geert Uytterhoeven wrote: > > > > + help > > > > + Improves the CPU scheduler's decision making when dealing with > > > > + MultiThreading at a cost of slightly increased overhead in some > > > > + places. If unsure say N here. > > > > > > So it should default to n? > > > > That's just help text that got carried around. Many of the architectures > > that had default y still had this text on. I suppose we can change it if > > someone cares. > > Please do so. How about we remove the recommendation like so? There are many help things that do not have a recommendation. Mostly these options add a little code and the most expensive bits tend to be gated by static_branch() so it really shouldn't be that bit of a burden. CONFIG_SMP was the big one for the scheduler, and Ingo recently removed that (he did an effective unifdef CONFIG_SMP=y on the scheduler code). --- diff --git a/arch/Kconfig b/arch/Kconfig index ebe08b9186ad..3d8e2025a4ac 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -57,7 +57,7 @@ config SCHED_SMT help Improves the CPU scheduler's decision making when dealing with MultiThreading at a cost of slightly increased overhead in some - places. If unsure say N here. + places. config SCHED_CLUSTER bool "Cluster scheduler support" @@ -77,7 +77,7 @@ config SCHED_MC help Multi-core scheduler support improves the CPU scheduler's decision making when dealing with multi-core CPU chips at a cost of slightly - increased overhead in some places. If unsure say N here. + increased overhead in some places. # Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL config HOTPLUG_CORE_SYNC