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 X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 64383C432BE for ; Wed, 28 Jul 2021 20:47:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4CDA861040 for ; Wed, 28 Jul 2021 20:47:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231952AbhG1UrZ (ORCPT ); Wed, 28 Jul 2021 16:47:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:58536 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231585AbhG1UrW (ORCPT ); Wed, 28 Jul 2021 16:47:22 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D29946023D; Wed, 28 Jul 2021 20:47:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627505240; bh=sUr9rUMhKmkWqkvIgSpyknDGwP3uVqdQ3DgS/1MhoDU=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=hlPrHFlKqp1KEi8yeYEu4CFuqn+n3pv6Nv8u+qx/kqIrC4S5VI3oOvRZCP4wtqcX4 6cIkMOcqeNBLlScKgKLlSQdal4mG9Q5GkFHqVgYeVjsgZ8YogFqmrcYdL9mGti/YUu lrlRj8P5QV/sFFUtumc5tyzfjtdnQXxmo2se32vrghw15834KkOj2DZHZtWt/c8nLe UMsP27sNIEGuoAvuU1VAyDBGnIsv/XFwjDhph43+Fq9xJy9P+VCDMmuTr5y+/FTRcn ecnlRgUkQxeVWa3UR7KG7Svom0IltQ6bcp4uAkKRX1RaZQJGhKO4glfFUIuGsMbqPY d8PhryUM3Dviw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id ACB355C048D; Wed, 28 Jul 2021 13:47:20 -0700 (PDT) Date: Wed, 28 Jul 2021 13:47:20 -0700 From: "Paul E. McKenney" To: Josh Triplett Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, Linus Torvalds Subject: Re: [PATCH v2 rcu 04/18] rcu: Weaken ->dynticks accesses and updates Message-ID: <20210728204720.GN4397@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20210721202042.GA1472052@paulmck-ThinkPad-P17-Gen-1> <20210721202127.2129660-4-paulmck@kernel.org> <20210728173715.GA9416@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 28, 2021 at 01:37:19PM -0700, Josh Triplett wrote: > On Wed, Jul 28, 2021 at 10:37:15AM -0700, Paul E. McKenney wrote: > > This change makes the memory ordering requirements > > more evident, and it might well also speed up the to-idle and from-idle > > fastpaths on some architectures. > > Cleaning up the memory ordering requirements certainly seems worthwhile. > But is there any straightforward benchmark that might quantify the > "might well also speed up" here? How much does weakening the memory > ordering buy us, in practice? None that I know of! Thanx, Paul