From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 96514C43441 for ; Thu, 15 Nov 2018 01:55:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5CB77214F1 for ; Thu, 15 Nov 2018 01:55:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5CB77214F1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727223AbeKOMBT (ORCPT ); Thu, 15 Nov 2018 07:01:19 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:37324 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726379AbeKOMBT (ORCPT ); Thu, 15 Nov 2018 07:01:19 -0500 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id wAF1rnms040388 for ; Wed, 14 Nov 2018 20:55:31 -0500 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0b-001b2d01.pphosted.com with ESMTP id 2nrx9qtew1-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 14 Nov 2018 20:55:31 -0500 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 15 Nov 2018 01:55:23 -0000 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id wAF1tM2d48824422 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 15 Nov 2018 01:55:22 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6345342041; Thu, 15 Nov 2018 01:55:22 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 805D742049; Thu, 15 Nov 2018 01:55:16 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.204.206]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Thu, 15 Nov 2018 01:55:16 +0000 (GMT) Date: Wed, 14 Nov 2018 17:55:12 -0800 From: Mike Rapoport To: Alexander Duyck Cc: Michal Hocko , akpm@linux-foundation.org, linux-mm@kvack.org, sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, davem@davemloft.net, pavel.tatashin@microsoft.com, mingo@kernel.org, kirill.shutemov@linux.intel.com, dan.j.williams@intel.com, dave.jiang@intel.com, rppt@linux.vnet.ibm.com, willy@infradead.org, vbabka@suse.cz, khalid.aziz@oracle.com, ldufour@linux.vnet.ibm.com, mgorman@techsingularity.net, yi.z.zhang@linux.intel.com Subject: Re: [mm PATCH v5 0/7] Deferred page init improvements References: <154145268025.30046.11742652345962594283.stgit@ahduyck-desk1.jf.intel.com> <20181114150742.GZ23419@dhcp22.suse.cz> <9e8218eb-80bf-fc02-ae56-42ccfddb572e@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9e8218eb-80bf-fc02-ae56-42ccfddb572e@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 18111501-0012-0000-0000-000002CAA9B5 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18111501-0013-0000-0000-000020FFBE5E Message-Id: <20181115015511.GB2353@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-11-14_20:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1811150015 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 14, 2018 at 04:50:23PM -0800, Alexander Duyck wrote: > > > On 11/14/2018 7:07 AM, Michal Hocko wrote: > >On Mon 05-11-18 13:19:25, Alexander Duyck wrote: > >>This patchset is essentially a refactor of the page initialization logic > >>that is meant to provide for better code reuse while providing a > >>significant improvement in deferred page initialization performance. > >> > >>In my testing on an x86_64 system with 384GB of RAM and 3TB of persistent > >>memory per node I have seen the following. In the case of regular memory > >>initialization the deferred init time was decreased from 3.75s to 1.06s on > >>average. For the persistent memory the initialization time dropped from > >>24.17s to 19.12s on average. This amounts to a 253% improvement for the > >>deferred memory initialization performance, and a 26% improvement in the > >>persistent memory initialization performance. > >> > >>I have called out the improvement observed with each patch. > > > >I have only glanced through the code (there is a lot of the code to look > >at here). And I do not like the code duplication and the way how you > >make the hotplug special. There shouldn't be any real reason for that > >IMHO (e.g. why do we init pfn-at-a-time in early init while we do > >pageblock-at-a-time for hotplug). I might be wrong here and the code > >reuse might be really hard to achieve though. > > Actually it isn't so much that hotplug is special. The issue is more that > the non-hotplug case is special in that you have to perform a number of > extra checks for things that just aren't necessary for the hotplug case. > > If anything I would probably need a new iterator that would be able to take > into account all the checks for the non-hotplug case and then provide ranges > of PFNs to initialize. > > >I am also not impressed by new iterators because this api is quite > >complex already. But this is mostly a detail. > > Yeah, the iterators were mostly an attempt at hiding some of the complexity. > Being able to break a loop down to just an iterator provding the start of > the range and the number of elements to initialize is pretty easy to > visualize, or at least I thought so. Just recently we had a discussion about overlapping for_each_mem_range() and for_each_mem_pfn_range(), but unfortunately it appears that no mailing list was cc'ed by the original patch author :( In short, there was a spelling fix in one of them and Michal pointed out that their functionality overlaps. I have no objection for for_each_free_mem_pfn_range_in_zone() and __next_mem_pfn_range_in_zone(), but probably we should consider unifying the older iterators before we introduce a new one? > >Thing I do not like is that you keep microptimizing PageReserved part > >while there shouldn't be anything fundamental about it. We should just > >remove it rather than make the code more complex. I fell more and more > >guilty to add there actually. > > I plan to remove it, but don't think I can get to it in this patch set. > > I was planning to submit one more iteration of this patch set early next > week, and then start focusing more on the removal of the PageReserved bit > for hotplug. I figure it is probably going to be a full patch set onto > itself and as you pointed out at the start of this email there is already > enough code to review without adding that. > > -- Sincerely yours, Mike.