From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) by kanga.kvack.org (Postfix) with ESMTP id 5F1B86B0269 for ; Wed, 24 Oct 2018 13:35:11 -0400 (EDT) Received: by mail-pg1-f198.google.com with SMTP id w15-v6so3439006pge.2 for ; Wed, 24 Oct 2018 10:35:11 -0700 (PDT) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTPS id i35-v6si5121021plg.361.2018.10.24.10.35.10 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Oct 2018 10:35:10 -0700 (PDT) Message-ID: <15bf78bdadd282b0587097d49cc39d0d7b662736.camel@linux.intel.com> Subject: Re: [mm PATCH v3 4/6] mm: Move hot-plug specific memory init into separate functions and optimize From: Alexander Duyck Date: Wed, 24 Oct 2018 10:35:09 -0700 In-Reply-To: <20181024152742.GJ18839@dhcp22.suse.cz> References: <20181015202456.2171.88406.stgit@localhost.localdomain> <20181015202716.2171.7284.stgit@localhost.localdomain> <20181017091824.GL18839@dhcp22.suse.cz> <20181024123640.GF18839@dhcp22.suse.cz> <40b17814b2a65531c5059e52a61c8f41b9603904.camel@linux.intel.com> <20181024152742.GJ18839@dhcp22.suse.cz> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, akpm@linux-foundation.org, pavel.tatashin@microsoft.com, dave.jiang@intel.com, linux-kernel@vger.kernel.org, willy@infradead.org, davem@davemloft.net, yi.z.zhang@linux.intel.com, khalid.aziz@oracle.com, rppt@linux.vnet.ibm.com, vbabka@suse.cz, sparclinux@vger.kernel.org, dan.j.williams@intel.com, ldufour@linux.vnet.ibm.com, mgorman@techsingularity.net, mingo@kernel.org, kirill.shutemov@linux.intel.com On Wed, 2018-10-24 at 17:27 +0200, Michal Hocko wrote: > On Wed 24-10-18 08:08:41, Alexander Duyck wrote: > > On Wed, 2018-10-24 at 14:36 +0200, Michal Hocko wrote: > > > On Wed 17-10-18 08:26:20, Alexander Duyck wrote: > > > [...] > > > > With that said I am also wondering if a possible solution to > > > > the complaints you had would be to look at just exporting the > > > > __init_pageblock function later and moving the call to > > > > memmap_init_zone_device out to the memremap or hotplug code > > > > when Dan gets the refactoring for HMM and memremap all sorted > > > > out. > > > > > > Why cannot we simply provide a constructor for each page by the > > > caller if there are special requirements? we currently have > > > alt_map > > > to do struct page allocation but nothing really prevents to make > > > it > > > more generic and control both allocation and initialization > > > whatever > > > suits a specific usecase. I really do not want make special cases > > > here and there. > > > > The advantage to the current __init_pageblock function is that we > > end up constructing everything we are going to write outside of the > > main loop and then are focused only on init. > > But we do really want move_pfn_range_to_zone to provide a usable pfn > range without any additional tweaks. If there are potential > optimizations to be done there then let's do it but please do not try > to micro optimize to the point that the interface doesn't make any > sense anymore. The actual difference between the two setups is not all that great. >>From the sound of things the ultimate difference between the ZONE_DEVICE pages and regular pages is the pgmap and if we want the reserved bit set or not. What I am providing with __init_pageblock at this point is a function that is flexible enough for us to be able to do either one and then just expose a different front end on it for the specific type of page we have to initialize. It works for regular hotplug, ZONE_DEVICE, and deferred memory initialization. The way I view it is that this funciton is a high performance multi-tasker, not something that is micro- optimized for any one specific function. Thanks. - Alex