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[209.132.180.67]) by mx.google.com with ESMTP id f186-v6si18806217pfa.336.2018.09.10.10.21.45; Mon, 10 Sep 2018 10:22:04 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728177AbeIJWPa (ORCPT + 99 others); Mon, 10 Sep 2018 18:15:30 -0400 Received: from mx2.suse.de ([195.135.220.15]:54760 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726709AbeIJWPa (ORCPT ); Mon, 10 Sep 2018 18:15:30 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 702E8AF44; Mon, 10 Sep 2018 17:20:22 +0000 (UTC) Date: Mon, 10 Sep 2018 10:20:11 -0700 From: Davidlohr Bueso To: Waiman Long Cc: John Hubbard , Daniel Jordan , linux-kernel@vger.kernel.org, "linux-mm@kvack.org" , Aaron Lu , alex.kogan@oracle.com, akpm@linux-foundation.org, boqun.feng@gmail.com, brouer@redhat.com, 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 Subject: Re: Plumbers 2018 - Performance and Scalability Microconference Message-ID: <20180910172011.GB3902@linux-r8p5> Mail-Followup-To: Waiman Long , John Hubbard , Daniel Jordan , linux-kernel@vger.kernel.org, "linux-mm@kvack.org" , Aaron Lu , alex.kogan@oracle.com, akpm@linux-foundation.org, boqun.feng@gmail.com, brouer@redhat.com, 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> <55b44432-ade5-f090-bfe7-ea20f3e87285@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <55b44432-ade5-f090-bfe7-ea20f3e87285@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 10 Sep 2018, Waiman Long wrote: >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. Yep, there are a few non-trivial workloads out there that flat out discourage thp, ie: redis to avoid latency issues. Thanks, Davidlohr