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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 A14AFC4360F for ; Tue, 2 Apr 2019 09:43:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6C130207E0 for ; Tue, 2 Apr 2019 09:43:46 +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="pVEmyxPF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729624AbfDBJnp (ORCPT ); Tue, 2 Apr 2019 05:43:45 -0400 Received: from merlin.infradead.org ([205.233.59.134]:53958 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726496AbfDBJnn (ORCPT ); Tue, 2 Apr 2019 05:43:43 -0400 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=S8MQn98qOqgzAiCgSbcL7hpe7vaijewxBXYXQRkz4Fw=; b=pVEmyxPFNEFM12bnA5XRPUND2 OZQd7bb7DLg5q6Iis1XoUbheAb1ETIdBMrUxgDQkb3vnTxzo2tNgAmbN+9346Fofd34mrz3a4cvlt aLuRVLEAY6wgnLBGtLAotY+iCvqePMmqjhMZErkk6/ZVIChOJlrPVQa0vHv7tlwFYkFQR/p519qgn 3bQjf1HgT3TtdwY8awLyl8Bzf4JdUzyfAvLQRQVD8dakzZJ5yY7G/NmtlNJGTRfH65im8I0sLKuOs pKFXH/Lz3XLQ5dHBpelMqH0A8B0Ey7j0ucJNxzZ8iOeBK78HwU7zvWGYUsNRNMlSejoMv3rQLXcwt E+fG1qvBA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hBFww-0000nk-PF; Tue, 02 Apr 2019 09:43:23 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 2E5572871E77C; Tue, 2 Apr 2019 11:43:20 +0200 (CEST) Date: Tue, 2 Apr 2019 11:43:20 +0200 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, steven.sistare@oracle.com, daniel.m.jordan@oracle.com, dave.dice@oracle.com, rahul.x.yadav@oracle.com Subject: Re: [PATCH v2 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock Message-ID: <20190402094320.GM11158@hirez.programming.kicks-ass.net> References: <20190329152006.110370-1-alex.kogan@oracle.com> <20190329152006.110370-4-alex.kogan@oracle.com> <60a3a2d8-d222-73aa-2df1-64c9d3fa3241@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <60a3a2d8-d222-73aa-2df1-64c9d3fa3241@redhat.com> 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 Mon, Apr 01, 2019 at 10:36:19AM -0400, Waiman Long wrote: > On 03/29/2019 11:20 AM, Alex Kogan wrote: > > +config NUMA_AWARE_SPINLOCKS > > + bool "Numa-aware spinlocks" > > + depends on NUMA > > + default y > > + help > > + Introduce NUMA (Non Uniform Memory Access) awareness into > > + the slow path of spinlocks. > > + > > + The kernel will try to keep the lock on the same node, > > + thus reducing the number of remote cache misses, while > > + trading some of the short term fairness for better performance. > > + > > + Say N if you want absolute first come first serve fairness. > > + > > The patch that I am looking for is to have a separate > numa_queued_spinlock_slowpath() that coexists with > native_queued_spinlock_slowpath() and > paravirt_queued_spinlock_slowpath(). At boot time, we select the most > appropriate one for the system at hand. Agreed; and until we have static_call, I think we can abuse the paravirt stuff for this. By the time we patch the paravirt stuff: check_bugs() alternative_instructions() apply_paravirt() we should already have enumerated the NODE topology and so nr_node_ids() should be set. So if we frob pv_ops.lock.queued_spin_lock_slowpath to numa_queued_spin_lock_slowpath before that, it should all get patched just right. That of course means the whole NUMA_AWARE_SPINLOCKS thing depends on PARAVIRT_SPINLOCK, which is a bit awkward...