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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 1F6D0C433F5 for ; Mon, 10 Sep 2018 17:09:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C332120880 for ; Mon, 10 Sep 2018 17:09:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C332120880 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728118AbeIJWEp convert rfc822-to-8bit (ORCPT ); Mon, 10 Sep 2018 18:04:45 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:47346 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726603AbeIJWEp (ORCPT ); Mon, 10 Sep 2018 18:04:45 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id ABCC95BCDE; Mon, 10 Sep 2018 17:09:40 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-55.bos.redhat.com [10.18.17.55]) by smtp.corp.redhat.com (Postfix) with ESMTP id 569AA2156889; Mon, 10 Sep 2018 17:09:36 +0000 (UTC) Subject: Re: Plumbers 2018 - Performance and Scalability Microconference To: John Hubbard , Daniel Jordan , linux-kernel@vger.kernel.org, "linux-mm@kvack.org" Cc: Aaron Lu , alex.kogan@oracle.com, akpm@linux-foundation.org, boqun.feng@gmail.com, brouer@redhat.com, dave@stgolabs.net, dave.dice@oracle.com, Dhaval Giani , ktkhai@virtuozzo.com, ldufour@linux.vnet.ibm.com, Pavel.Tatashin@microsoft.com, paulmck@linux.vnet.ibm.com, shady.issa@oracle.com, tariqt@mellanox.com, tglx@linutronix.de, tim.c.chen@intel.com, vbabka@suse.cz, yang.shi@linux.alibaba.com, shy828301@gmail.com, Huang Ying , subhra.mazumdar@oracle.com, Steven Sistare , jwadams@google.com, ashwinch@google.com, sqazi@google.com, Shakeel Butt , walken@google.com, rientjes@google.com, junaids@google.com, Neha Agarwal References: <1dc80ff6-f53f-ae89-be29-3408bf7d69cc@oracle.com> <35c2c79f-efbe-f6b2-43a6-52da82145638@nvidia.com> From: Waiman Long Organization: Red Hat Message-ID: <55b44432-ade5-f090-bfe7-ea20f3e87285@redhat.com> Date: Mon, 10 Sep 2018 13:09:36 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <35c2c79f-efbe-f6b2-43a6-52da82145638@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Content-Language: en-US X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Mon, 10 Sep 2018 17:09:41 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Mon, 10 Sep 2018 17:09:41 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'longman@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/08/2018 12:13 AM, John Hubbard wrote: > > Hi Daniel and all, > > I'm interested in the first 3 of those 4 topics, so if it doesn't conflict with HMM topics or > fix-gup-with-dma topics, I'd like to attend. GPUs generally need to access large chunks of > memory, and that includes migrating (dma-copying) pages around. > > So for example a multi-threaded migration of huge pages between normal RAM and GPU memory is an > intriguing direction (and I realize that it's a well-known topic, already). Doing that properly > (how many threads to use?) seems like it requires scheduler interaction. > > It's also interesting that there are two main huge page systems (THP and Hugetlbfs), and I sometimes > wonder the obvious thing to wonder: are these sufficiently different to warrant remaining separate, > long-term? Yes, I realize they're quite different in some ways, but still, one wonders. :) One major difference between hugetlbfs and THP is that the former has to be explicitly managed by the applications that use it whereas the latter is done automatically without the applications being aware that THP is being used at all. Performance wise, THP may or may not increase application performance depending on the exact memory access pattern, though the chance is usually higher that an application will benefit than suffer from it. If an application know what it is doing, using hughtblfs can boost performance more than it can ever achieved by THP. Many large enterprise applications, like Oracle DB, are using hugetlbfs and explicitly disable THP. So unless THP can improve its performance to a level that is comparable to hugetlbfs, I won't see the later going away. Cheers, Longman