From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id 6B5888E00AE for ; Fri, 4 Jan 2019 10:32:49 -0500 (EST) Received: by mail-ed1-f72.google.com with SMTP id c18so34868902edt.23 for ; Fri, 04 Jan 2019 07:32:49 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id 26-v6si5357082ejl.106.2019.01.04.07.32.47 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 04 Jan 2019 07:32:47 -0800 (PST) Date: Fri, 4 Jan 2019 16:32:45 +0100 From: Michal Hocko Subject: Re: [PATCH v3] mm/page_owner: fix for deferred struct page init Message-ID: <20190104153245.GV31793@dhcp22.suse.cz> References: <20190103165927.GU31793@dhcp22.suse.cz> <5d8f3a98-a954-c8ab-83d9-2f94c614f268@lca.pw> <20190103190715.GZ31793@dhcp22.suse.cz> <62e96e34-7ea9-491a-b5b6-4828da980d48@lca.pw> <20190103202235.GE31793@dhcp22.suse.cz> <20190104130906.GO31793@dhcp22.suse.cz> <20190104151737.GT31793@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Qian Cai Cc: akpm@linux-foundation.org, Pavel.Tatashin@microsoft.com, mingo@kernel.org, mgorman@techsingularity.net, iamjoonsoo.kim@lge.com, tglx@linutronix.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Fri 04-01-19 10:25:12, Qian Cai wrote: > On 1/4/19 10:17 AM, Michal Hocko wrote: > > On Fri 04-01-19 10:01:40, Qian Cai wrote: > >> On 1/4/19 8:09 AM, Michal Hocko wrote: > >>>> Here is the number without DEFERRED_STRUCT_PAGE_INIT. > >>>> > >>>> == page_ext_init() after page_alloc_init_late() == > >>>> Node 0, zone DMA: page owner found early allocated 0 pages > >>>> Node 0, zone DMA32: page owner found early allocated 7009 pages > >>>> Node 0, zone Normal: page owner found early allocated 85827 pages > >>>> Node 4, zone Normal: page owner found early allocated 75063 pages > >>>> > >>>> == page_ext_init() before kmemleak_init() == > >>>> Node 0, zone DMA: page owner found early allocated 0 pages > >>>> Node 0, zone DMA32: page owner found early allocated 6654 pages > >>>> Node 0, zone Normal: page owner found early allocated 41907 pages > >>>> Node 4, zone Normal: page owner found early allocated 41356 pages > >>>> > >>>> So, it told us that it will miss tens of thousands of early page allocation call > >>>> sites. > >>> > >>> This is an answer for the first part of the question (how much). The > >>> second is _do_we_care_? > >> > >> Well, the purpose of this simple "ugly" ifdef is to avoid a regression for the > >> existing page_owner users with DEFERRED_STRUCT_PAGE_INIT deselected that would > >> start to miss tens of thousands early page allocation call sites. > > > > I am pretty sure we will hear about that when that happens. And act > > accordingly. > > > >> The other option I can think of to not hurt your eyes is to rewrite the whole > >> page_ext_init(), init_page_owner(), init_debug_guardpage() to use all early > >> functions, so it can work in both with DEFERRED_STRUCT_PAGE_INIT=y and without. > >> However, I have a hard-time to convince myself it is a sensible thing to do. > > > > Or simply make the page_owner initialization only touch the already > > initialized memory. Have you explored that option as well? > > Yes, a proof-of-concept version is v1 where ends up with more ifdefs due to > dealing with all the low-level details, > > https://lore.kernel.org/lkml/20181220060303.38686-1-cai@lca.pw/ That is obviously not what I've had in mind. We have __init_single_page which initializes a single struct page. Is there any way to hook page_ext initialization there? -- Michal Hocko SUSE Labs