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 AFABAC64E8A for ; Mon, 30 Nov 2020 09:35:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5588B2076E for ; Mon, 30 Nov 2020 09:35:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="DZmGHuBX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726756AbgK3JfN (ORCPT ); Mon, 30 Nov 2020 04:35:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58034 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725965AbgK3JfN (ORCPT ); Mon, 30 Nov 2020 04:35:13 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E9DB8C0613CF; Mon, 30 Nov 2020 01:34:32 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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=0rWZ/IKLgX5YBtYlsGOEnzcxhpN2D379f2O4Lio8snw=; b=DZmGHuBX23XyOb0cYXxLwKvpB+ 1QFJSgOTkI0TdQcuEDlwzcyxfvK3NW4jFlga+VMD1+hut7ZfTUVDPiUZg3xzF3qLlP+Ac1USFi6qp 4YPToAcqP+rNdlu7fqFgH0OGt0wmYCFT/6L1/DE07qbTOPFDXO4mKDdJhGVoRLRDUPLytj7/QB3QO 7btaCKCgshCA358zEjjiqbMdS8WOI/Oz2FA5XL/ZvrcoogYQU/ql+fcUXzEV2kuq7/40oBjjGMzwG PUnV/3WJfZ+yQycDAIuAN1vCwkquC+gl0cJ06EY6rBnJh+aLw1wUU17oDBEXk4K5uqm6mAfKXQMv4 eCafddhg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kjfZa-0001G5-CH; Mon, 30 Nov 2020 09:34:18 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 278DA3003E1; Mon, 30 Nov 2020 10:34:17 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 12B1720107BE2; Mon, 30 Nov 2020 10:34:17 +0100 (CET) Date: Mon, 30 Nov 2020 10:34:17 +0100 From: Peter Zijlstra To: Andy Lutomirski Cc: Nicholas Piggin , LKML , X86 ML , Mathieu Desnoyers , Arnd Bergmann , linux-arch , linuxppc-dev , Linux-MM , Anton Blanchard Subject: Re: [PATCH 6/8] lazy tlb: shoot lazies, a non-refcounting lazy tlb option Message-ID: <20201130093417.GI3092@hirez.programming.kicks-ass.net> References: <20201128160141.1003903-1-npiggin@gmail.com> <20201128160141.1003903-7-npiggin@gmail.com> <20201130093000.GM2414@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201130093000.GM2414@hirez.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 30, 2020 at 10:30:00AM +0100, Peter Zijlstra wrote: > On Sat, Nov 28, 2020 at 07:54:57PM -0800, Andy Lutomirski wrote: > > This means that mm_cpumask operations won't need to be full barriers > > forever, and we might not want to take the implied full barriers in > > set_bit() and clear_bit() for granted. > > There is no implied full barrier for those ops. Neither ARM nor Power implies any ordering on those ops. But Power has some of the worst atomic performance in the world despite of that. IIRC they don't do their LL/SC in L1.