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=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 C3F9BC43441 for ; Wed, 14 Nov 2018 15:07:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8CF1521780 for ; Wed, 14 Nov 2018 15:07:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8CF1521780 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 S1733289AbeKOBLV (ORCPT ); Wed, 14 Nov 2018 20:11:21 -0500 Received: from mx2.suse.de ([195.135.220.15]:42116 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728116AbeKOBLV (ORCPT ); Wed, 14 Nov 2018 20:11:21 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 0C2D8AEFA; Wed, 14 Nov 2018 15:07:43 +0000 (UTC) Date: Wed, 14 Nov 2018 16:07:42 +0100 From: Michal Hocko 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 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> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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