From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 24DCFC433EF for ; Mon, 30 May 2022 13:16:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236454AbiE3NQo (ORCPT ); Mon, 30 May 2022 09:16:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232433AbiE3NQm (ORCPT ); Mon, 30 May 2022 09:16:42 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94DB364ED; Mon, 30 May 2022 06:16:41 -0700 (PDT) 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=obYBR28FbpSJAp30gAezgU5OKkXGsA5r4rJru5EBzPo=; b=Jg0O7ZkawyIbRQYiQh/fe1DLO5 pOHRuud+4bXV4vL70xI5fSEpFwKXx0k5p4uGlhacsWYGmIHWHSsVGbRyuXlR3uffdhblS/7bbXNKi wFgq5v6bZdIQTW8lSpbYaBomCcTk41s8jINRbPxdE4s4Z5HP0k2UJAAhioDN9Bj4fRvk324HcvURl Qk5VRSvmcYMXz1ORFPtzMgA/OtlL7xWpuu/TcLqh7cvKTFCHVCClBOSJFTmCfDAT8CY8PPs4AzG8T 3Nnct7Q0l8e+WE/0fLFV7vgC8CiW8FRkiGpRXWR9rMLz6kxKhh527AUvtIxDXX7zzjuga2UOZifWq U9dDap5w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nvfG2-004Umx-3z; Mon, 30 May 2022 13:16:30 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id DB035980DE7; Mon, 30 May 2022 15:16:27 +0200 (CEST) Date: Mon, 30 May 2022 15:16:27 +0200 From: Peter Zijlstra To: Frederic Weisbecker Cc: Juri Lelli , Tejun Heo , Waiman Long , LKML , "Paul E . McKenney" , Paul Gortmaker , Johannes Weiner , Marcelo Tosatti , Phil Auld , Zefan Li , Daniel Bristot de Oliveira , Nicolas Saenz Julienne , rcu@vger.kernel.org Subject: Re: [RFC PATCH 4/4] cpuset: Support RCU-NOCB toggle on v2 root partitions Message-ID: References: <20220526225141.GA1214445@lothringen> <9e44bb00-955a-dbc6-a863-be649e0c701f@redhat.com> <20220527083018.n43nc73vuuzm5ixo@localhost.localdomain> <20220530004049.GA1251147@lothringen> <20220530105650.GA1257179@lothringen> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220530105650.GA1257179@lothringen> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 30, 2022 at 12:56:50PM +0200, Frederic Weisbecker wrote: > > This is ABI, you can't walk back on it. I would suggest starting with an > > 'all feature' isolation. Only if there's real demand for something more > > fine-grained add that on top. Simple first etc. > > That's actually my worry. If we start with an all in one ABI, how do we later > mix that up with more finegrained features? Like what will be the behaviour of: > > cpuset.isolation.rcu_nocb = 0 > cpuset.isolation.all = 1 Well clearly that doesn't make sense. I was more thinking along the lines of cgroup.subtree_control, where instead all features are enabled by default. But only if there's a real usecase, otherwise there's no point in providing such knobs.