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=-17.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 C16E4C433E0 for ; Thu, 25 Feb 2021 17:54:37 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5661164F3B for ; Thu, 25 Feb 2021 17:54:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5661164F3B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D697C6B0006; Thu, 25 Feb 2021 12:54:36 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D40656B006C; Thu, 25 Feb 2021 12:54:36 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C307F8D0001; Thu, 25 Feb 2021 12:54:36 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0170.hostedemail.com [216.40.44.170]) by kanga.kvack.org (Postfix) with ESMTP id AB9EC6B0006 for ; Thu, 25 Feb 2021 12:54:36 -0500 (EST) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 6FCF3B788 for ; Thu, 25 Feb 2021 17:54:36 +0000 (UTC) X-FDA: 77857540152.13.B806684 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf14.hostedemail.com (Postfix) with ESMTP id 09B21C0007C3 for ; Thu, 25 Feb 2021 17:54:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614275674; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=byOfTija5+suCvG20txiiotsxrvATo8BhNy2ZFJ78Pk=; b=TQTeAoxpKfqJkCFB5Uw/9qiPFSB2J+5JrKsXKtJQQgBE2VMKqZp8iIDbaOh1i25l4WOORd Xa4gLZ8rjUOgUPzZrT5wh97KB98686RGZ+njIwqL6smZsFmOdJ5BcjeYb51kdxj5ijPeCz p/kibwM0i9Y5seHXbSPsM7sy07Bi1uw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-595-aGNrTLL-NNSZVLIgLJIO3g-1; Thu, 25 Feb 2021 12:54:19 -0500 X-MC-Unique: aGNrTLL-NNSZVLIgLJIO3g-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C09853CE8; Thu, 25 Feb 2021 17:54:16 +0000 (UTC) Received: from [10.36.114.58] (ovpn-114-58.ams2.redhat.com [10.36.114.58]) by smtp.corp.redhat.com (Postfix) with ESMTP id D24365D9D2; Thu, 25 Feb 2021 17:54:11 +0000 (UTC) Subject: Re: [PATCH v7 1/1] mm/page_alloc.c: refactor initialization of struct page for holes in memory layout To: Mike Rapoport Cc: Mike Rapoport , Andrew Morton , Andrea Arcangeli , Baoquan He , Borislav Petkov , Chris Wilson , "H. Peter Anvin" , Ingo Molnar , Linus Torvalds , =?UTF-8?Q?=c5=81ukasz_Majczak?= , Mel Gorman , Michal Hocko , Qian Cai , "Sarvela, Tomi P" , Thomas Gleixner , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, x86@kernel.org References: <20210224153950.20789-1-rppt@kernel.org> <20210224153950.20789-2-rppt@kernel.org> <515b4abf-ff07-a43a-ac2e-132c33681886@redhat.com> <20210225170629.GE1854360@linux.ibm.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <2c7ad47f-f545-8716-5fa2-7d3173141f76@redhat.com> Date: Thu, 25 Feb 2021 18:54:10 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210225170629.GE1854360@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Stat-Signature: cotr5e54uwms5hrxiueo3rbznfzghxiq X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 09B21C0007C3 Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf14; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=216.205.24.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614275666-608832 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 25.02.21 18:06, Mike Rapoport wrote: > On Thu, Feb 25, 2021 at 04:59:06PM +0100, David Hildenbrand wrote: >> On 24.02.21 16:39, Mike Rapoport wrote: >>> From: Mike Rapoport >>> >>> There could be struct pages that are not backed by actual physical memory. >>> This can happen when the actual memory bank is not a multiple of >>> SECTION_SIZE or when an architecture does not register memory holes >>> reserved by the firmware as memblock.memory. >>> >>> Such pages are currently initialized using init_unavailable_mem() function >>> that iterates through PFNs in holes in memblock.memory and if there is a >>> struct page corresponding to a PFN, the fields of this page are set to >>> default values and it is marked as Reserved. >>> >>> init_unavailable_mem() does not take into account zone and node the page >>> belongs to and sets both zone and node links in struct page to zero. >>> >>> Before commit 73a6e474cb37 ("mm: memmap_init: iterate over memblock regions >>> rather that check each PFN") the holes inside a zone were re-initialized >>> during memmap_init() and got their zone/node links right. However, after >>> that commit nothing updates the struct pages representing such holes. >>> >>> On a system that has firmware reserved holes in a zone above ZONE_DMA, for >>> instance in a configuration below: >>> >>> # grep -A1 E820 /proc/iomem >>> 7a17b000-7a216fff : Unknown E820 type >>> 7a217000-7bffffff : System RAM >>> >>> unset zone link in struct page will trigger >>> >>> VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page); >>> >>> because there are pages in both ZONE_DMA32 and ZONE_DMA (unset zone link >>> in struct page) in the same pageblock. >>> >>> Interleave initialization of the unavailable pages with the normal >>> initialization of memory map, so that zone and node information will be >>> properly set on struct pages that are not backed by the actual memory. >>> >>> With this change the pages for holes inside a zone will get proper >>> zone/node links and the pages that are not spanned by any node will get >>> links to the adjacent zone/node. >>> >>> Fixes: 73a6e474cb37 ("mm: memmap_init: iterate over memblock regions rather that check each PFN") >>> Signed-off-by: Mike Rapoport >>> Reported-by: Qian Cai >>> Reported-by: Andrea Arcangeli >>> Reviewed-by: Baoquan He >>> --- >>> mm/page_alloc.c | 147 +++++++++++++++++++++--------------------------- >>> 1 file changed, 64 insertions(+), 83 deletions(-) >>> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index 3e93f8b29bae..a11a9acde708 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -6280,12 +6280,60 @@ static void __meminit zone_init_free_lists(struct zone *zone) >>> } >>> } >>> +#if !defined(CONFIG_FLAT_NODE_MEM_MAP) >>> +/* >>> + * Only struct pages that correspond to ranges defined by memblock.memory >>> + * are zeroed and initialized by going through __init_single_page() during >>> + * memmap_init_zone(). >>> + * >>> + * But, there could be struct pages that correspond to holes in >>> + * memblock.memory. This can happen because of the following reasons: >>> + * - phyiscal memory bank size is not necessarily the exact multiple of the >>> + * arbitrary section size >>> + * - early reserved memory may not be listed in memblock.memory >>> + * - memory layouts defined with memmap= kernel parameter may not align >>> + * nicely with memmap sections >>> + * >>> + * Explicitly initialize those struct pages so that: >>> + * - PG_Reserved is set >>> + * - zone and node links point to zone and node that span the page >>> + */ >>> +static u64 __meminit init_unavailable_range(unsigned long spfn, >>> + unsigned long epfn, >>> + int zone, int node) >>> +{ >>> + unsigned long pfn; >>> + u64 pgcnt = 0; >>> + >>> + for (pfn = spfn; pfn < epfn; pfn++) { >>> + if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) { >>> + pfn = ALIGN_DOWN(pfn, pageblock_nr_pages) >>> + + pageblock_nr_pages - 1; >>> + continue; >>> + } >>> + __init_single_page(pfn_to_page(pfn), pfn, zone, node); >>> + __SetPageReserved(pfn_to_page(pfn)); >>> + pgcnt++; >>> + } >>> + >>> + return pgcnt; >>> +} >>> +#else >>> +static inline u64 init_unavailable_range(unsigned long spfn, unsigned long epfn, >>> + int zone, int node) >>> +{ >>> + return 0; >>> +} >>> +#endif >>> + >>> void __meminit __weak memmap_init_zone(struct zone *zone) >>> { >>> unsigned long zone_start_pfn = zone->zone_start_pfn; >>> unsigned long zone_end_pfn = zone_start_pfn + zone->spanned_pages; >>> int i, nid = zone_to_nid(zone), zone_id = zone_idx(zone); >>> + static unsigned long hole_pfn = 0; >>> unsigned long start_pfn, end_pfn; >>> + u64 pgcnt = 0; >>> for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) { >>> start_pfn = clamp(start_pfn, zone_start_pfn, zone_end_pfn); >>> @@ -6295,7 +6343,23 @@ void __meminit __weak memmap_init_zone(struct zone *zone) >>> memmap_init_range(end_pfn - start_pfn, nid, >>> zone_id, start_pfn, zone_end_pfn, >>> MEMINIT_EARLY, NULL, MIGRATE_MOVABLE); >>> + >>> + if (hole_pfn < start_pfn) >>> + pgcnt += init_unavailable_range(hole_pfn, start_pfn, >>> + zone_id, nid); >>> + hole_pfn = end_pfn; >>> } >>> + >>> +#ifdef CONFIG_SPARSEMEM >>> + end_pfn = round_up(zone_end_pfn, PAGES_PER_SECTION); >>> + if (hole_pfn < end_pfn) >>> + pgcnt += init_unavailable_range(hole_pfn, end_pfn, >>> + zone_id, nid); >> >> We might still double-initialize PFNs when two zones overlap within a >> section, correct? > > You mean that a section crosses zones boundary? > I don't think it's that important. > >> This might worth documenting - also, you might want to >> take some of the original comment the accompanied this code. > > The original comment was not exactly right, I believe the comment above > init_unavailable_range() better describes what's going on there. Ah, okay - as long as it's documented I'm happy :) -- Thanks, David / dhildenb