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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 89792C433EF for ; Tue, 12 Oct 2021 19:05:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6363A60F3A for ; Tue, 12 Oct 2021 19:05:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231243AbhJLTHP (ORCPT ); Tue, 12 Oct 2021 15:07:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:59678 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234764AbhJLTFb (ORCPT ); Tue, 12 Oct 2021 15:05:31 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CC15E60E09; Tue, 12 Oct 2021 19:03:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1634065405; bh=41ZgXWvJqX6cNDtIQEONvKgmB5mmWoA3gdKQ9esdOVk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=0blFRlQK51dgu5FJKOqFr1L6t3mVBbILK25yhOQvYbDuiPk4p/Xlmnu0gZa3KlXFG piH0prBBWaQ3m2nPz29jPiijWku3bv4yF077HespUJB5jDIWOWf1wBVn/h4JIWCJTW NDX7+IpzU2qmix0bc6QUcCtixPz37PA42oiuSsT8= Date: Tue, 12 Oct 2021 12:03:22 -0700 From: Andrew Morton To: Jason Gunthorpe Cc: Alex Sierra , Felix.Kuehling@amd.com, linux-mm@kvack.org, rcampbell@nvidia.com, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, hch@lst.de, jglisse@redhat.com, apopple@nvidia.com Subject: Re: [PATCH v1 00/12] MEMORY_DEVICE_COHERENT for CPU-accessible coherent device memory Message-Id: <20211012120322.224d88dad0188160a40dd615@linux-foundation.org> In-Reply-To: <20211012185629.GZ2744544@nvidia.com> References: <20211012171247.2861-1-alex.sierra@amd.com> <20211012113957.53f05928dd60f3686331fede@linux-foundation.org> <20211012185629.GZ2744544@nvidia.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Tue, 12 Oct 2021 15:56:29 -0300 Jason Gunthorpe wrote: > > To what other uses will this infrastructure be put? > > > > Because I must ask: if this feature is for one single computer which > > presumably has a custom kernel, why add it to mainline Linux? > > Well, it certainly isn't just "one single computer". Overall I know of > about, hmm, ~10 *datacenters* worth of installations that are using > similar technology underpinnings. > > "Frontier" is the code name for a specific installation but as the > technology is proven out there will be many copies made of that same > approach. > > The previous program "Summit" was done with NVIDIA GPUs and PowerPC > CPUs and also included a very similar capability. I think this is a > good sign that this coherently attached accelerator will continue to > be a theme in computing going foward. IIRC this was done using out of > tree kernel patches and NUMA localities. > > Specifically with CXL now being standardized and on a path to ubiquity > I think we will see an explosion in deployments of coherently attached > accelerator memory. This is the high end trickling down to wider > usage. > > I strongly think many CXL accelerators are going to want to manage > their on-accelerator memory in this way as it makes universal sense to > want to carefully manage memory access locality to optimize for > performance. Thanks. Can we please get something like the above into the [0/n] changelog? Along with any other high-level info which is relevant? It's rather important. "why should I review this", "why should we merge this", etc.