From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3y2txG09KLzDsPp for ; Thu, 28 Sep 2017 22:17:37 +1000 (AEST) Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v8SCFXGA004817 for ; Thu, 28 Sep 2017 08:17:34 -0400 Received: from e06smtp14.uk.ibm.com (e06smtp14.uk.ibm.com [195.75.94.110]) by mx0a-001b2d01.pphosted.com with ESMTP id 2d8yr4c3km-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 28 Sep 2017 08:17:33 -0400 Received: from localhost by e06smtp14.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 28 Sep 2017 13:17:31 +0100 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 14:17:22 +0200 MIME-Version: 1.0 In-Reply-To: <20170925163443.260d6092160ec704e2b04653@linux-foundation.org> Content-Type: text/plain; charset=utf-8; format=flowed Message-Id: List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi, 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 do agree and I could just encourage people to do so :/ > I'll be taking a close look at it all over the next couple of weeks. Thanks Andrew for giving it a close look. > 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. The benefit is only for multi-threaded processes. But even on *small* systems with 16 CPUs, there is a real 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(?). I did test with kernbench, involving gcc/ld which are not multi-threaded, AFAIK, and I didn't see any impact. But if you know additional test I should give a try, please advise. Regarding ebizzy, it was designed to simulate web server's activity, so I guess there will be improvements when running real web servers. > Even things as simple as impact upon > single-threaded pagefault-intensive workloads and its effect upon > CONFIG_SMP=n .text size? > > 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. The other use-case I'm aware of is on memory database, where performance improvements is really significant, as I mentioned in the header of my series. Cheers, Laurent.