From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753146AbdI1M3S (ORCPT ); Thu, 28 Sep 2017 08:29:18 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:49780 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753118AbdI1M3R (ORCPT ); Thu, 28 Sep 2017 08:29:17 -0400 Subject: Re: [PATCH v3 00/20] Speculative page faults To: Andrew Morton , Alexei Starovoitov Cc: Paul McKenney , Peter Zijlstra , kirill@shutemov.name, Andi Kleen , Michal Hocko , dave@stgolabs.net, Jan Kara , Matthew Wilcox , Benjamin Herrenschmidt , Michael Ellerman , Paul Mackerras , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Will Deacon , Sergey Senozhatsky , "linux-kernel@vger.kernel.org" , linux-mm , haren@linux.vnet.ibm.com, Anshuman Khandual , npiggin@gmail.com, bsingharora@gmail.com, Tim Chen , linuxppc-dev@lists.ozlabs.org, "x86@kernel.org" References: <20170925163443.260d6092160ec704e2b04653@linux-foundation.org> From: Laurent Dufour Date: Thu, 28 Sep 2017 14:29:02 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <20170925163443.260d6092160ec704e2b04653@linux-foundation.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 17092812-0008-0000-0000-0000049AEC91 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17092812-0009-0000-0000-00001E2C3E78 Message-Id: <924a79af-6d7a-316a-1eee-3aebbfd4addf@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-09-28_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1707230000 definitions=main-1709280185 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Andrew, On 26/09/2017 01:34, Andrew Morton wrote: > On Mon, 25 Sep 2017 09:27:43 -0700 Alexei Starovoitov wrote: > >> On Mon, Sep 18, 2017 at 12:15 AM, Laurent Dufour >> wrote: >>> Despite the unprovable lockdep warning raised by Sergey, I didn't get any >>> feedback on this series. >>> >>> Is there a chance to get it moved upstream ? >> >> what is the status ? >> We're eagerly looking forward for this set to land, >> since we have several use cases for tracing that >> will build on top of this set as discussed at Plumbers. > > There has been sadly little review and testing so far :( > > I'll be taking a close look at it all over the next couple of weeks. > > One terribly important thing (especially for a patchset this large and > intrusive) is the rationale for merging it: the justification, usually > in the form of end-user benefit. > > Laurent's [0/n] provides some nice-looking performance benefits for > workloads which are chosen to show performance benefits(!) but, alas, > no quantitative testing results for workloads which we may suspect will > be harmed by the changes(?). Even things as simple as impact upon > single-threaded pagefault-intensive workloads and its effect upon > CONFIG_SMP=n .text size? I forgot to mention in my previous email the impact on the .text section. Here are the metrics I got : .text size UP SMP Delta 4.13-mmotm 8444201 8964137 6.16% '' +spf 8452041 8971929 6.15% Delta 0.09% 0.09% No major impact as you could see. Thanks, Laurent > If you have additional usecases then please, spell them out for us in > full detail so we can better understand the benefits which this > patchset provides. >