From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753265AbdHQP3z (ORCPT ); Thu, 17 Aug 2017 11:29:55 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:51709 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753009AbdHQP3y (ORCPT ); Thu, 17 Aug 2017 11:29:54 -0400 Subject: Re: [v6 05/15] mm: don't accessed uninitialized struct pages From: Pasha Tatashin To: Michal Hocko Cc: linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org, kasan-dev@googlegroups.com, borntraeger@de.ibm.com, heiko.carstens@de.ibm.com, davem@davemloft.net, willy@infradead.org, ard.biesheuvel@linaro.org, will.deacon@arm.com, catalin.marinas@arm.com, sam@ravnborg.org References: <1502138329-123460-1-git-send-email-pasha.tatashin@oracle.com> <1502138329-123460-6-git-send-email-pasha.tatashin@oracle.com> <20170811093746.GF30811@dhcp22.suse.cz> <8444cb2b-b134-e9fc-a458-1ba7b22a8df1@oracle.com> <20170814114755.GI19063@dhcp22.suse.cz> Message-ID: <139b7d83-12a3-d584-0461-d01a79df5d2b@oracle.com> Date: Thu, 17 Aug 2017 11:28:23 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Source-IP: aserv0022.oracle.com [141.146.126.234] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Michal, I've been looking through this code again, and I think your suggestion will work. I did not realize this iterator already exist: for_each_free_mem_range() basically iterates through (memory && !reserved) This is exactly what we need here. So, I will update this patch to use this iterator, which will simplify it. Pasha On 08/14/2017 09:51 AM, Pasha Tatashin wrote: >>> mem_init() >>> free_all_bootmem() >>> free_low_memory_core_early() >>> for_each_reserved_mem_region() >>> reserve_bootmem_region() >>> init_reserved_page() <- if this is deferred reserved page >>> __init_single_pfn() >>> __init_single_page() >>> >>> So, currently, we are using the value of page->flags to figure out if >>> this >>> page has been initialized while being part of deferred page, but this >>> is not >>> going to work for this project, as we do not zero the memory that is >>> backing >>> the struct pages, and size the value of page->flags can be anything. >> >> True, this is the initialization part I've missed in one of the previous >> patches already. Would it be possible to only iterate over !reserved >> memory blocks instead? Now that we discard all the metadata later it >> should be quite easy to do for_each_memblock_type, no? > > Hi Michal, > > Clever suggestion to add a new iterator to go through unreserved > existing memory, I do not think there is this iterator available, so it > would need to be implemented, using similar approach to what I have done > with a call back. > > However, there is a different reason, why I took this current approach. > > Daniel Jordan is working on a ktask support: > https://lkml.org/lkml/2017/7/14/666 > > He and I discussed on how to multi-thread struct pages initialization > within memory nodes using ktasks. Having this callback interface makes > that multi-threading quiet easy, improving the boot performance further, > with his prototype we saw x4-6 improvements (using 4-8 threads per > node). Reducing the total time it takes to initialize all struct pages > on machines with terabytes of memory to less than one second. > > Pasha