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=-5.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 6EC61C43387 for ; Fri, 4 Jan 2019 15:17:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4071821872 for ; Fri, 4 Jan 2019 15:17:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546615061; bh=ywe9joJGeBVcMoPzA0ZtSCE1ggF7Ge+Wr/ZTV3rXKZY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=2MG1TbRSzAz5QLJRZCT7+TGkc4QCZF6LsHoCyDF0tqfiyBFv06rUaHLx0GTNRamvK mynkbF8PEf1uNzmip+/k+IBmqzVOoLRcmfaeCA0UQLpaN/A5LpV09Wyuq0TYfTucvn ZLeo4LqbbslBoy1X8V3TsH6jXF0gEU1HuuzopF0w= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727296AbfADPRk (ORCPT ); Fri, 4 Jan 2019 10:17:40 -0500 Received: from mx2.suse.de ([195.135.220.15]:54186 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726488AbfADPRk (ORCPT ); Fri, 4 Jan 2019 10:17:40 -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 B229FAFDA; Fri, 4 Jan 2019 15:17:38 +0000 (UTC) Date: Fri, 4 Jan 2019 16:17:37 +0100 From: Michal Hocko 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 Subject: Re: [PATCH v3] mm/page_owner: fix for deferred struct page init Message-ID: <20190104151737.GT31793@dhcp22.suse.cz> References: <20190103115114.GL31793@dhcp22.suse.cz> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 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? Look, I am trying to push for a clean solution. Hacks I have seen so far are not convincing. You have identified a regression and as such I would consider the most straightforward to revert the buggy commit. If you want to improve the situation then I would suggest to think about something that is more robust than ifdefed hacks. It might be more work but it also might be a better thing long term. If you think I am asking too much then you are free to ignore my opinion. I am not a maintainer of the page_owner code. -- Michal Hocko SUSE Labs