From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 870CF1C9ECA for ; Thu, 10 Oct 2024 07:58:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728547140; cv=none; b=NQx+iNfFgYXU4lYU2y8id1RJjKBD64jfhCXcTKPMI2ltooL/W2AMhRUfKHPLNsxIX3gpk6qxzsCVvhm0emQ0SRj8SHSvAclBJEYt4NyzqzOyU1luptX9eiKOu3eepoEpGq7s3ib2xWVXCo7mIKquc7UEZYCa5BQ8eWek8jgTMJI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728547140; c=relaxed/simple; bh=ADMoqZ+Lq+yC0ScC7nQDVocebHDA8uXxzjW3BAki/ec=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=oWPMDcf5Ci3TNiDtL0KeDT24TWR+1Uh0jF7vwTKt9HxpjyJXfErhLQNJS+tgI+PfaYmwqxrRxo3SIKIDuEj5c40mL2Q0U81mtNhlSzxBgpMyfYiKWZ1SndAeMQNVtLgAjrwonTgXt2QT/RJozz13yqk/lJNyBgzlnP8Aj65HUW4= 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=qRCMnrSk; arc=none smtp.client-ip=90.155.50.34 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="qRCMnrSk" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; 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=ADMoqZ+Lq+yC0ScC7nQDVocebHDA8uXxzjW3BAki/ec=; b=qRCMnrSkkBt8HCvHOOFSI79Ory HqUuRdGaA1PiDH/GaIX6oNusfRGGoP18xnTicz0MvcajMQtswjBvGrLgJ6tiEXX1v7joSfpnvObCe sjmO438ndCOf0iID0mjIaBT3T8GWNTwYW4GTwAGFjMYA57Ruz0PYgXghJSxnsQo7E0g2m2rE+UWXg GFvCdbTWjXeui2PfZAz4Ugu8p0vUCMpCI2JK4i0YvOKvXq2zvAS309dA12vFsGmrM7DWbELHcLEfb bNWXMnUoF8ixqigzdV4GVImpfgdm5Cqxrf85/p3mh0MoBTRw5kFPmRs9RlS0Dj45xRB6OlnUatvXu nuaGB65g==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1syo4Q-000000076AX-03UW; Thu, 10 Oct 2024 07:58:50 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 437F330088D; Thu, 10 Oct 2024 09:58:50 +0200 (CEST) Date: Thu, 10 Oct 2024 09:58:50 +0200 From: Peter Zijlstra To: "Paul E. McKenney" Cc: Ankur Arora , linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@kernel.org, bigeasy@linutronix.de, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, frederic@kernel.org, efault@gmx.de Subject: Re: [PATCH 2/7] rcu: limit PREEMPT_RCU configurations Message-ID: <20241010075850.GZ17263@noisy.programming.kicks-ass.net> References: <20241009165411.3426937-1-ankur.a.arora@oracle.com> <20241009165411.3426937-3-ankur.a.arora@oracle.com> <20241009180117.GS17263@noisy.programming.kicks-ass.net> <37af80bd-a54f-4ee4-9175-6f0f27b685a0@paulmck-laptop> <20241009205218.GW17263@noisy.programming.kicks-ass.net> <28bcac6a-6aee-456a-8022-5eef9ec08eaa@paulmck-laptop> 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: <28bcac6a-6aee-456a-8022-5eef9ec08eaa@paulmck-laptop> On Wed, Oct 09, 2024 at 02:16:43PM -0700, Paul E. McKenney wrote: > Because we don't need a bunch of people surprised by this change in > behavior. I'm not sure what change in behaviour; Lazy is brand spanking new, it will have new behaviour not in line with previous modes. Just put in the help text that if you're looking for a reality closer to the old Voluntary to use PREEMPT_RCU=n. In reality very few people will care, because distros will be running PREEMPT_DYNAMIC and the 3 people doing their own thing ought to be savvy enough to deal with things, no?