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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH,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 67F0BC4646D for ; Wed, 8 Aug 2018 17:22:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2189221766 for ; Wed, 8 Aug 2018 17:22:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Z56Aywdg" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2189221766 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729267AbeHHTmx (ORCPT ); Wed, 8 Aug 2018 15:42:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:34288 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727295AbeHHTmx (ORCPT ); Wed, 8 Aug 2018 15:42:53 -0400 Received: from localhost (unknown [69.71.4.100]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C07CC216F4; Wed, 8 Aug 2018 17:22:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1533748934; bh=WbFLpkB48cWNNVo4a6UbymRHF8em7Fk2LnPG1R/+ya8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Z56Aywdgc80wK8xLDOSSOwpj58RfC6lqkxt/jxtVGw0Szalv654+DCJbd3nCXZzz1 8LDqb+273onexzn5S5LHp2fROgWqY/81F7aWtbzTiEn0NRjlBiVwH6DqFp8qt9ZOG1 ALaDMZCfPI6Qb/Z41/afiMigpXxAdDbsrEUPgM/s= Date: Wed, 8 Aug 2018 12:22:11 -0500 From: Bjorn Helgaas To: Punit Agrawal Cc: Bjorn Helgaas , Lorenzo Pieralisi , Jeremy Linton , linux-arm , Catalin Marinas , Will Deacon , Jiang Liu , linux-pci@vger.kernel.org, Linux Kernel Mailing List , linux-acpi@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] arm64: PCI: Remove node-local allocations when initialising host controller Message-ID: <20180808172211.GD49411@bhelgaas-glaptop.roam.corp.google.com> References: <20180801173132.19739-1-punit.agrawal@arm.com> <38ad03ba-2658-98c8-1888-0aa3bfb59bd4@arm.com> <20180802143319.GA13512@red-moon> <87eff85364.fsf@e105922-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87eff85364.fsf@e105922-lin.cambridge.arm.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 08, 2018 at 03:44:03PM +0100, Punit Agrawal wrote: > Bjorn Helgaas writes: > > On Thu, Aug 2, 2018 at 9:33 AM Lorenzo Pieralisi > > wrote: > >> On Wed, Aug 01, 2018 at 02:38:51PM -0500, Jeremy Linton wrote: > >> > >> Jiang Liu does not work on the kernel anymore so we won't know > >> anytime soon the reasoning behind commit 965cd0e4a5e5 > >> > >> > On 08/01/2018 12:31 PM, Punit Agrawal wrote: > >> > >Memory for host controller data structures is allocated local to the > >> > >node to which the controller is associated with. This has been the > >> > >behaviour since support for ACPI was added in > >> > >commit 0cb0786bac15 ("ARM64: PCI: Support ACPI-based PCI host controller"). > >> > > >> > Which was apparently influenced by: > >> > > >> > 965cd0e4a5e5 x86, PCI, ACPI: Use kmalloc_node() to optimize for performance > >> > > >> > Was there an actual use-case behind that change? > >> > > >> > I think this fixes the immediate boot problem, but if there is any > >> > perf advantage it seems wise to keep it... Particularly since x86 > >> > seems to be doing the node sanitation in pci_acpi_root_get_node(). > >> > >> I am struggling to see the perf advantage of allocating a struct > >> that the PCI controller will never read/write from a NUMA node that > >> is local to the PCI controller, happy to be corrected if there is > >> a sound rationale behind that. > > > > If there is no reason to use kzalloc_node() here, we shouldn't use it. > > > > But we should use it (or not use it) consistently across arches. I do > > not believe there is an arch-specific reason to be different. > > Currently, pci_acpi_scan_root() uses kzalloc_node() on x86 and arm64, > > but kzalloc() on ia64. They all ought to be the same. > > From my understanding, arm64 use of kzalloc_node() was derived from the > x86 version. Maybe somebody familiar with behaviour on x86 can provide > input here. If you want to remove use of kzalloc_node(), I'm fine with that as long as you do it for x86 at the same time (maybe separate patches, but at least in the same series). I don't see any evidence in 965cd0e4a5e5 ("x86, PCI, ACPI: Use kmalloc_node() to optimize for performance") that it actually improves performance, so I'd be inclined to just use kzalloc(). Bjorn