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 B38571C9EB3 for ; Thu, 10 Oct 2024 07:50:46 +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=1728546648; cv=none; b=X5YrLyfuDWBv5F0Ffy8rJGWRKjZgjWEsLuNCFRMocigu07/61JIy+HpURfZaYoeo6+DNyEuWM9lGftD5CFOrAOfP3bsbdP78EPAKy2sWf1rAKI0Fv3AVCrHuaq7fxGJbHpuuqIsQC4qgl2OdZDTE+LjUSeds60sRyED/tNLJ0fk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728546648; c=relaxed/simple; bh=N6of/suUMYod6OV/wY/Wl8R5O3YAAiagzxYyyF3dWA0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QrdoMYWpyQvjhL4b/lrm+zShY7TMOEcoXMNu7NDrKDwPahdnu9vCQFhWeIwDAexdnD1SOBKvFb8zCFq07bnxC8jpjCpOWWSny5NunWxxQYhLUwybm4ZTu1S4esngT6LFmq0NIQSRfIVnjGwlcFaocqM6iBbiiiMButvDla4ya2g= 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=lHSSwgHT; 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="lHSSwgHT" 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=xa+OI90OGbpzsM7ExACJJXhgr3sapIrB3JJbXovs1w0=; b=lHSSwgHTt8Oeh5Qepndmui+yOa BZbRxsF9x+NyrNv8mrkgiWT7DxI6tdepXD73inG9AEGC7g31kWFwRtlTWSFBvBQAB7eMgAEkFoULZ Twj8VfxvZkoUBdgsQZL9pfUCtWI9NIIkh4Kx9cReM7z7OsC4wQGCT5zugHifyuUcmcx/i3tFeelDZ 1lPmvUv0q2KJQj8747R/hkAUvnORV8x3Q2YC/Bs4UP7YrbJot1oSsnm9qjbMklg4eLllBU54fmOxV ec9tEfsiYADliXfN3MW2VABQocEGSVSKvgnzZSO2gcy2B/88ZEqTkp9PwRFICrm8lFwH5o1X6S3jI B0yT7myA==; 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 1synwR-000000074nE-0c7i; Thu, 10 Oct 2024 07:50:35 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 2937930088D; Thu, 10 Oct 2024 09:50:35 +0200 (CEST) Date: Thu, 10 Oct 2024 09:50:35 +0200 From: Peter Zijlstra To: Christoph Hellwig Cc: bigeasy@linutronix.de, tglx@linutronix.de, mingo@kernel.org, linux-kernel@vger.kernel.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, ankur.a.arora@oracle.com, efault@gmx.de Subject: Re: [PATCH 3/5] sched: Enable PREEMPT_DYNAMIC for PREEMPT_RT Message-ID: <20241010075035.GX17263@noisy.programming.kicks-ass.net> References: <20241007074609.447006177@infradead.org> <20241007075055.441622332@infradead.org> 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: On Wed, Oct 09, 2024 at 11:52:36PM -0700, Christoph Hellwig wrote: > On Mon, Oct 07, 2024 at 09:46:12AM +0200, Peter Zijlstra wrote: > > In order to enable PREEMPT_DYNAMIC for PREEMPT_RT, remove PREEMPT_RT > > from the 'Preemption Model' choice. Strictly speaking PREEMPT_RT is > > not a change in how preemption works, but rather it makes a ton more > > code preemptible. > > > > Notably, take away NONE and VOLATILE options for PREEMPT_RT, they make > > no sense (but are techincally possible). > > Should we take away NONE entirely because it is kinda silly? > > Just a bystander here, but the explosion of different preemption models > is a bit silly and not really helpful to users. The end goal is to get rid of Voluntary and None, but getting there will require more work. A lot of careful work to be sure. In the end we should be rid of those two preemption models and the cond_resched() and much of the random need_resched() hackery they brought. But we can't do it all at once, so yeah, we need to grow extra crap before we can take out the old stuff. Nothing new there, but I get your frustration.