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Tue, 11 Sep 2018 00:29:08 GMT Received: from abhmp0004.oracle.com (abhmp0004.oracle.com [141.146.116.10]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id w8B0T4hk008664; Tue, 11 Sep 2018 00:29:04 GMT Received: from [192.168.1.218] (/73.143.71.164) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 10 Sep 2018 17:29:04 -0700 Subject: Re: Plumbers 2018 - Performance and Scalability Microconference To: John Hubbard , Waiman Long , 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> <20180910172011.GB3902@linux-r8p5> <78fa0507-4789-415b-5b9c-18e3fcefebab@nvidia.com> From: Daniel Jordan Message-ID: <3db2b742-9e09-a934-e4ef-c87465e6715a@oracle.com> Date: Mon, 10 Sep 2018 20:29:00 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <78fa0507-4789-415b-5b9c-18e3fcefebab@nvidia.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9012 signatures=668708 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=969 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1809110004 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/10/18 1:34 PM, John Hubbard wrote: > On 9/10/18 10:20 AM, Davidlohr Bueso wrote: >> On Mon, 10 Sep 2018, Waiman Long wrote: >>> On 09/08/2018 12:13 AM, John Hubbard wrote: > [...] >>>> 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. >> > > Yes, the need for guaranteed, available-now huge pages in some cases is > understood. That's not the quite same as saying that there have to be two different > subsystems, though. Nor does it even necessarily imply that the pool has to be > reserved in the same way as hugetlbfs does it...exactly. > > So I'm wondering if THP behavior can be made to mimic hugetlbfs enough (perhaps > another option, in addition to "always, never, madvise") that we could just use > THP in all cases. But the "transparent" could become a sliding scale that could > go all the way down to "opaque" (hugetlbfs behavior). Leaving the interface aside, the idea that we could deduplicate redundant parts of the hugetlbfs and THP implementations, without user-visible change, seems promising.