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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 11FE4C433B4 for ; Thu, 22 Apr 2021 07:00:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CF2A060BD3 for ; Thu, 22 Apr 2021 07:00:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234877AbhDVHBB (ORCPT ); Thu, 22 Apr 2021 03:01:01 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:17812 "EHLO szxga07-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229962AbhDVHA7 (ORCPT ); Thu, 22 Apr 2021 03:00:59 -0400 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga07-in.huawei.com (SkyGuard) with ESMTP id 4FQpCV628sz7vy7; Thu, 22 Apr 2021 14:57:58 +0800 (CST) Received: from [10.174.177.244] (10.174.177.244) by DGGEMS405-HUB.china.huawei.com (10.3.19.205) with Microsoft SMTP Server id 14.3.498.0; Thu, 22 Apr 2021 15:00:20 +0800 Subject: Re: [PATCH v2 0/4] arm64: drop pfn_valid_within() and simplify pfn_valid() To: Mike Rapoport , CC: Andrew Morton , Anshuman Khandual , Ard Biesheuvel , "Catalin Marinas" , David Hildenbrand , "Marc Zyngier" , Mark Rutland , Mike Rapoport , Will Deacon , , , References: <20210421065108.1987-1-rppt@kernel.org> From: Kefeng Wang Message-ID: <9aa68d26-d736-3b75-4828-f148964eb7f0@huawei.com> Date: Thu, 22 Apr 2021 15:00:20 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20210421065108.1987-1-rppt@kernel.org> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [10.174.177.244] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/4/21 14:51, Mike Rapoport wrote: > From: Mike Rapoport > > Hi, > > These patches aim to remove CONFIG_HOLES_IN_ZONE and essentially hardwire > pfn_valid_within() to 1. > > The idea is to mark NOMAP pages as reserved in the memory map and restore > the intended semantics of pfn_valid() to designate availability of struct > page for a pfn. > > With this the core mm will be able to cope with the fact that it cannot use > NOMAP pages and the holes created by NOMAP ranges within MAX_ORDER blocks > will be treated correctly even without the need for pfn_valid_within. > > The patches are only boot tested on qemu-system-aarch64 so I'd really > appreciate memory stress tests on real hardware. > > If this actually works we'll be one step closer to drop custom pfn_valid() > on arm64 altogether. Hi Mike，I have a question, without HOLES_IN_ZONE, the pfn_valid_within() in move_freepages_block()->move_freepages() will be optimized, if there are holes in zone, the 'struce page'(memory map) for pfn range of hole will be free by free_memmap(), and then the page traverse in the zone(with holes) from move_freepages() will meet the wrong page， then it could panic at PageLRU(page) test, check link[1], "The idea is to mark NOMAP pages as reserved in the memory map", I see the patch2 check memblock_is_nomap() in memory region of memblock, but it seems that memblock_mark_nomap() is not called(maybe I missed), then memmap_init_reserved_pages() won't work, so should the HOLES_IN_ZONE still be needed for generic mm code? [1] https://lore.kernel.org/linux-arm-kernel/541193a6-2bce-f042-5bb2-88913d5f1047@arm.com/