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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,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 5FE54C432BE for ; Wed, 28 Jul 2021 20:37:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 459C261019 for ; Wed, 28 Jul 2021 20:37:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231623AbhG1Uh3 (ORCPT ); Wed, 28 Jul 2021 16:37:29 -0400 Received: from wnew3-smtp.messagingengine.com ([64.147.123.17]:59393 "EHLO wnew3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231126AbhG1Uh1 (ORCPT ); Wed, 28 Jul 2021 16:37:27 -0400 Received: from compute4.internal (compute4.nyi.internal [10.202.2.44]) by mailnew.west.internal (Postfix) with ESMTP id E37912B011CF; Wed, 28 Jul 2021 16:37:23 -0400 (EDT) Received: from mailfrontend1 ([10.202.2.162]) by compute4.internal (MEProxy); Wed, 28 Jul 2021 16:37:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= joshtriplett.org; h=date:from:to:cc:subject:message-id :references:mime-version:content-type:in-reply-to; s=fm1; bh=S2P Y/gCouDsnhtUs0tus40I2EUyvx7oxWdFXqNb0GiY=; b=cxOaSAQGypolDmil1LN LNLJvZGseVYVizr8wghHvKh2+yXEYqcxDKTCZZSuBMkMAgWMQOjawQ+0nADZMLbm U+BA0BwU7Vo4XB5ZEhEGvtfkUsW24RNUmu+pw3DTo8oC1PW3yY7Q2Gbk5ox/rSUN iOVE9Qhu0UTEcDshVsiJqJgN87bbgeqc7kR0YECL8dAMgqeVARqKtiNZLHl9oshb AW9/6kg3j+SJaFxHS5J5gWf5C0ANHVIOOcvjnO0OR023O1f7AQPs/g63MOKqD5r2 kYMsj1KeWc/GpkwS9gSFkGx5MJXGIhPf343+mxrX6kBf8OF2Mhgr3FrSkSUUHL5j 75w== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm3; bh=S2PY/g CouDsnhtUs0tus40I2EUyvx7oxWdFXqNb0GiY=; b=A1o3esHeZKs+bKdjblmwPS ShVrlK5G8j/09UyQ5dt6pt1M5Vf1Xs4G6ehmba6X9XSSUdvP/y6+QZfLe5Z9TghM tHBhMD4qvdzlC4beQl+JTbDdDY8tNCQCfN0q5K95CXDFL9EDD29P93MQ4lcuZOqK ikUQNSNlDBg1I4HOe/b39LL3rGE++Nfb3/N6B8Tmb3YXqM7wbP+mfHK9ysM9dUEm JVRN/Nr4lA2uS7cmO80j5kdKzMxC9hGHXtcgrFjXxX+m/LpRsqkE7R3HPo8o7Rry gS1osYTpJ7vAO4LR8LJP3Y2imckOY3d3f/omFpD/IqXTvXn6aoKiIwtElunjaWkA == X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvtddrgeelgdduudehucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepfffhvffukfhfgggtuggjsehttdertddttddvnecuhfhrohhmpeflohhshhcu vfhrihhplhgvthhtuceojhhoshhhsehjohhshhhtrhhiphhlvghtthdrohhrgheqnecugg ftrfgrthhtvghrnhepgedtgfefgefhveeglefgfeeigeduueehkeektdeuueetgfehffev geeuieetheetnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrh homhepjhhoshhhsehjohhshhhtrhhiphhlvghtthdrohhrgh X-ME-Proxy: Received: by mail.messagingengine.com (Postfix) with ESMTPA; Wed, 28 Jul 2021 16:37:20 -0400 (EDT) Date: Wed, 28 Jul 2021 13:37:19 -0700 From: Josh Triplett To: "Paul E. McKenney" 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: 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: <20210728173715.GA9416@paulmck-ThinkPad-P17-Gen-1> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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?