From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot1-f69.google.com (mail-ot1-f69.google.com [209.85.210.69]) by kanga.kvack.org (Postfix) with ESMTP id 95C306B2B90 for ; Thu, 22 Nov 2018 06:52:23 -0500 (EST) Received: by mail-ot1-f69.google.com with SMTP id c33so4581490otb.18 for ; Thu, 22 Nov 2018 03:52:23 -0800 (PST) Received: from foss.arm.com (usa-sjc-mx-foss1.foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id 8si20740171oth.87.2018.11.22.03.52.22 for ; Thu, 22 Nov 2018 03:52:22 -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> From: Anshuman Khandual Message-ID: Date: Thu, 22 Nov 2018 17:22:19 +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: Dave Hansen , Keith Busch , linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org Cc: Greg Kroah-Hartman , Rafael Wysocki , Dan Williams On 11/19/2018 11:07 PM, Dave Hansen wrote: > On 11/18/18 9:44 PM, Anshuman Khandual wrote: >> IIUC NUMA re-work in principle involves these functional changes >> >> 1. Enumerating compute and memory nodes in heterogeneous environment (short/medium term) > > This patch set _does_ that, though. > >> 2. Enumerating memory node attributes as seen from the compute nodes (short/medium term) > > It does that as well (a subset at least). > > It sounds like the subset that's being exposed is insufficient for yo > We did that because we think doing anything but a subset in sysfs will > just blow up sysfs: MAX_NUMNODES is as high as 1024, so if we have 4 > attributes, that's at _least_ 1024*1024*4 files if we expose *all* > combinations. Each permutation need not be a separate file inside all possible NODE X (/sys/devices/system/node/nodeX) directories. It can be a top level file enumerating various attribute values for a given (X, Y) node pair based on an offset something like /proc/pid/pagemap. > > Do we agree that sysfs is unsuitable for exposing attributes in this manner? > Yes, for individual files. But this can be worked around with an offset based access from a top level global attributes file as mentioned above. Is there any particular advantage of using individual files for each given attribute ? I was wondering that a single unsigned long (u64) will be able to pack 8 different attributes where each individual attribute values can be abstracted out in 8 bits.