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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 EDB7BC2D0DB for ; Thu, 23 Jan 2020 15:29:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BDBD02064C for ; Thu, 23 Jan 2020 15:29:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="j1j6sCnf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728904AbgAWP3y (ORCPT ); Thu, 23 Jan 2020 10:29:54 -0500 Received: from merlin.infradead.org ([205.233.59.134]:34794 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727847AbgAWP3y (ORCPT ); Thu, 23 Jan 2020 10:29:54 -0500 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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=B/n7W4E7uJv5pAkHx8ZqbqbrQSUi/FNUw9Ppcu+la6k=; b=j1j6sCnf43FehruEfnqskrYLt Nn8vL0JG757sO7HS9jy/OW4qN7Xix2ztFpJGjhG0QLLNLKrSVprKwN1Sm3w4t2G1KuTivtLxuDNow srmx8d4BRDA1cZVtL6pPeoES1PflMknut7Qo5+xQo4tgayMAJo90FilPtFtGDWghaDrVt4qeBqnX/ jkQYNsbBaH8pe2tklc/irJIS4pachSjxnlh9EF7llzHd7lOWKQaqSi5iO5UGtwVpOK2z8O/H++xNM IUmNO6YlaNgdwixRiYPWm027TpZwMb8tRhf1G4ApegWcUN+G3gVCW7J+VmdIQ/F6/Es0/QM44NRFi gDzwJ0FxA==; 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 1iueQ6-0007ex-8F; Thu, 23 Jan 2020 15:29:22 +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 2261E300693; Thu, 23 Jan 2020 16:27:38 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 42C712B63FCAF; Thu, 23 Jan 2020 16:29:18 +0100 (CET) Date: Thu, 23 Jan 2020 16:29:18 +0100 From: Peter Zijlstra To: Waiman Long Cc: Alex Kogan , linux@armlinux.org.uk, mingo@redhat.com, will.deacon@arm.com, arnd@arndb.de, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, bp@alien8.de, hpa@zytor.com, x86@kernel.org, guohanjun@huawei.com, jglauber@marvell.com, steven.sistare@oracle.com, daniel.m.jordan@oracle.com, dave.dice@oracle.com Subject: Re: [PATCH v9 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock Message-ID: <20200123152918.GD14879@hirez.programming.kicks-ass.net> References: <20200115035920.54451-1-alex.kogan@oracle.com> <20200115035920.54451-4-alex.kogan@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 23, 2020 at 09:15:55AM -0500, Waiman Long wrote: > On 1/14/20 10:59 PM, Alex Kogan wrote: > > +static int __init cna_init_nodes(void) > > +{ > > + unsigned int cpu; > > + > > + /* > > + * this will break on 32bit architectures, so we restrict > > + * the use of CNA to 64bit only (see arch/x86/Kconfig) > > + */ > > + BUILD_BUG_ON(sizeof(struct cna_node) > sizeof(struct qnode)); > > + /* we store an ecoded tail word in the node's @locked field */ > > + BUILD_BUG_ON(sizeof(u32) > sizeof(unsigned int)); > > + > > + for_each_possible_cpu(cpu) > > + cna_init_nodes_per_cpu(cpu); > > + > > + return 0; > > +} > > +early_initcall(cna_init_nodes); > > + > > I just realized that you shouldn't call cna_init_nodes as an > early_initcall. Instead, > > > +/* > > + * Switch to the NUMA-friendly slow path for spinlocks when we have > > + * multiple NUMA nodes in native environment, unless the user has > > + * overridden this default behavior by setting the numa_spinlock flag. > > + */ > > +void __init cna_configure_spin_lock_slowpath(void) > > +{ > > + if ((numa_spinlock_flag == 1) || > > + (numa_spinlock_flag == 0 && nr_node_ids > 1 && > > + pv_ops.lock.queued_spin_lock_slowpath == > > + native_queued_spin_lock_slowpath)) { > > + pv_ops.lock.queued_spin_lock_slowpath = > > + __cna_queued_spin_lock_slowpath; > > + > > + pr_info("Enabling CNA spinlock\n"); > > + } > > +} > > call it when it is sure that CNA spinlock is going to be used. At this > point, the system is still in UP mode and the slowpath will not be called. Indeed, let me go fix that!