From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot1-f71.google.com (mail-ot1-f71.google.com [209.85.210.71]) by kanga.kvack.org (Postfix) with ESMTP id B10996B474B for ; Tue, 27 Nov 2018 05:15:41 -0500 (EST) Received: by mail-ot1-f71.google.com with SMTP id s12so9868582otc.12 for ; Tue, 27 Nov 2018 02:15:41 -0800 (PST) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id p10si1477432otl.267.2018.11.27.02.15.39 for ; Tue, 27 Nov 2018 02:15:40 -0800 (PST) Subject: Re: [PATCH 0/7] ACPI HMAT memory sysfs representation References: <20181114224902.12082-1-keith.busch@intel.com> <1ed406b2-b85f-8e02-1df0-7c39aa21eca9@arm.com> <4ea6e80f-80ba-6992-8aa0-5c2d88996af7@intel.com> <9015e51a-3584-7bb2-cc5e-25b0ec8e5494@intel.com> From: Anshuman Khandual Message-ID: <325d0e69-053a-ae9c-eede-7cdf28b1dbd6@arm.com> Date: Tue, 27 Nov 2018 15:45:40 +0530 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams , Dave Hansen Cc: Keith Busch , Linux Kernel Mailing List , Linux ACPI , Linux MM , Greg KH , "Rafael J. Wysocki" On 11/26/2018 11:38 PM, Dan Williams wrote: > On Mon, Nov 26, 2018 at 8:42 AM Dave Hansen wrote: >> >> On 11/23/18 1:13 PM, Dan Williams wrote: >>>> A new system call makes total sense to me. I have the same concern >>>> about the completeness of what's exposed in sysfs, I just don't see a >>>> _route_ to completeness with sysfs itself. Thus, the minimalist >>>> approach as a first step. >>> Outside of platform-firmware-id to Linux-numa-node-id what other >>> userspace API infrastructure does the kernel need to provide? It seems >>> userspace enumeration of memory attributes is fully enabled once the >>> firmware-to-Linux identification is established. >> >> It would be nice not to have each app need to know about each specific >> platform's firmware. > > The app wouldn't need to know if it uses a common library. Whether the > library calls into the kernel or not is an implementation detail. If > it is information that only the app cares about and the kernel does > not consume, why have a syscall? If we just care about platform-firmware-id <--> Linux-numa-node-id mapping and fetching memory attribute from the platform (and hiding implementation details in a library) then the following interface should be sufficient. /sys/devices/system/node/nodeX/platform_id But as the series proposes (and rightly so) kernel needs to start providing ABI interfaces for memory attributes instead of hiding them in libraries.