From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id 736106B000A for ; Wed, 14 Nov 2018 10:07:45 -0500 (EST) Received: by mail-ed1-f71.google.com with SMTP id y35so4963273edb.5 for ; Wed, 14 Nov 2018 07:07:45 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id n14-v6si1587110edt.57.2018.11.14.07.07.43 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 14 Nov 2018 07:07:44 -0800 (PST) Date: Wed, 14 Nov 2018 16:07:42 +0100 From: Michal Hocko Subject: Re: [mm PATCH v5 0/7] Deferred page init improvements Message-ID: <20181114150742.GZ23419@dhcp22.suse.cz> References: <154145268025.30046.11742652345962594283.stgit@ahduyck-desk1.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <154145268025.30046.11742652345962594283.stgit@ahduyck-desk1.jf.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Alexander Duyck Cc: 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 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. I am also not impressed by new iterators because this api is quite complex already. But this is mostly a detail. 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. -- Michal Hocko SUSE Labs