From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id 109438E0001 for ; Mon, 10 Sep 2018 13:20:25 -0400 (EDT) Received: by mail-ed1-f72.google.com with SMTP id r25-v6so7374325edc.7 for ; Mon, 10 Sep 2018 10:20:25 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id e18-v6si1630530edb.332.2018.09.10.10.20.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 10 Sep 2018 10:20:23 -0700 (PDT) Date: Mon, 10 Sep 2018 10:20:11 -0700 From: Davidlohr Bueso Subject: Re: Plumbers 2018 - Performance and Scalability Microconference Message-ID: <20180910172011.GB3902@linux-r8p5> 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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