From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) by kanga.kvack.org (Postfix) with ESMTP id 135BC6B0008 for ; Wed, 8 Aug 2018 13:22:16 -0400 (EDT) Received: by mail-pg1-f198.google.com with SMTP id a26-v6so1347436pgw.7 for ; Wed, 08 Aug 2018 10:22:16 -0700 (PDT) Received: from mail.kernel.org (mail.kernel.org. [198.145.29.99]) by mx.google.com with ESMTPS id p81-v6si4932982pfi.345.2018.08.08.10.22.14 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 08 Aug 2018 10:22:14 -0700 (PDT) Date: Wed, 8 Aug 2018 12:22:11 -0500 From: Bjorn Helgaas 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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