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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 4AB7AC4708E for ; Sat, 29 May 2021 06:41:28 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C267A611ED for ; Sat, 29 May 2021 06:41:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C267A611ED Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 5B06D6B0070; Sat, 29 May 2021 02:41:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 588976B0071; Sat, 29 May 2021 02:41:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4503A8D0001; Sat, 29 May 2021 02:41:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0135.hostedemail.com [216.40.44.135]) by kanga.kvack.org (Postfix) with ESMTP id 131446B0070 for ; Sat, 29 May 2021 02:41:27 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id A6500BEF2 for ; Sat, 29 May 2021 06:41:26 +0000 (UTC) X-FDA: 78193322172.17.C6DB57A Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf19.hostedemail.com (Postfix) with ESMTP id 0ACB79001E45 for ; Sat, 29 May 2021 06:41:14 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 9ACAB68B05; Sat, 29 May 2021 08:41:24 +0200 (CEST) Date: Sat, 29 May 2021 08:41:24 +0200 From: Christoph Hellwig To: Felix Kuehling Cc: Jason Gunthorpe , Felix Kuehling , dri-devel@lists.freedesktop.org, linux-mm@kvack.org, jglisse@redhat.com, amd-gfx@lists.freedesktop.org, akpm@linux-foundation.org, hch@lst.de Subject: Re: [RFC PATCH 0/5] Support DEVICE_GENERIC memory in migrate_vma_* Message-ID: <20210529064124.GC15834@lst.de> References: <20210527230809.3701-1-Felix.Kuehling@amd.com> <20210528130816.GM1002214@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-Rspamd-Queue-Id: 0ACB79001E45 Authentication-Results: imf19.hostedemail.com; dkim=none; dmarc=none; spf=none (imf19.hostedemail.com: domain of hch@lst.de has no SPF policy when checking 213.95.11.211) smtp.mailfrom=hch@lst.de X-Rspamd-Server: rspam04 X-Stat-Signature: 8fwqab1hb3idm7jms176tnw54cadwm5o X-HE-Tag: 1622270474-389249 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, May 28, 2021 at 11:56:36AM -0400, Felix Kuehling wrote: > Am 2021-05-28 um 9:08 a.m. schrieb Jason Gunthorpe: > > On Thu, May 27, 2021 at 07:08:04PM -0400, Felix Kuehling wrote: > >> Now we're trying to migrate data to and from that memory using the > >> migrate_vma_* helpers so we can support page-based migration in our > >> unified memory allocations, while also supporting CPU access to those > >> pages. > > So you have completely coherent and indistinguishable GPU and CPU > > memory and the need of migration is basicaly alot like NUMA policy > > choice - get better access locality? > > Yes. For a typical GPU compute application it means the GPU gets the > best bandwidth/latency, and the CPU can coherently access the results > without page faults and migrations. That's especially valuable for > applications with persistent compute kernels that want to exploit > concurrency between CPU and GPU. So why not expose the GPU memory as a CPUless memory node?