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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id BC476E784AC for ; Mon, 2 Oct 2023 11:25:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 52CA78D0020; Mon, 2 Oct 2023 07:25:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4DCCA8D0001; Mon, 2 Oct 2023 07:25:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 37D8C8D0020; Mon, 2 Oct 2023 07:25:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 246A38D0001 for ; Mon, 2 Oct 2023 07:25:23 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id E16EEC0225 for ; Mon, 2 Oct 2023 11:25:22 +0000 (UTC) X-FDA: 81300290484.19.438B848 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf17.hostedemail.com (Postfix) with ESMTP id A2DB140005 for ; Mon, 2 Oct 2023 11:25:20 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=VrNMCW8G; spf=pass (imf17.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1696245920; h=from:from:sender: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:dkim-signature; bh=bOneOzTrSmpqtG0qhnCChNvIYEoW+1fDAEnSmXjPvzQ=; b=hKrJ/6HWON1VmAcBS2G9OUCFPJJ4nK1BzgUs/GmY0VStZpR0rAupEYsi6n3W/XYUKlSLd0 moGv3js0nzu6wfueCrdWwXPZoRjwW22M+9voHvDC51ysxPB/1+YGMbZQGe+y/18hCOmy+0 GwtDmuWhWCk9dDiulqTxUkW3oV3ePjk= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1696245920; a=rsa-sha256; cv=none; b=zBrVRaRq3orZuNrrjIzFBjPEiM60f1b0XBH2i1IEJe79GqQPNOHoczqKK14Hoyrv2rzb5a 1QgeR2NNsTKM5fsNDwUaHWZkYWK+Wh3ucUqk5b49HnBSMZeWHat/bkuodEfls3LjMlpI6k 0s+P4N6DA4yADpuwU0+AWgzqHx5y4tc= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=VrNMCW8G; spf=pass (imf17.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1696245920; 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=bOneOzTrSmpqtG0qhnCChNvIYEoW+1fDAEnSmXjPvzQ=; b=VrNMCW8G2hc0G8ZqrtlwXZ+8nAWQzs18HbQtdPbemcFaXOWgaK6ml5m/xQRJ9n3zfWL0eB gNTVmD/GI8wlAeLDve3fkHa7QtnVuZZAD2rWSJUC9lFFfufhOuggdtsQHdg7UvFttzk6vy Rv2DSe7+swgBBmTkNIG+YS4+xVhCRHY= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-376-IMWWCsElMS6tpQECHbUAKQ-1; Mon, 02 Oct 2023 07:25:13 -0400 X-MC-Unique: IMWWCsElMS6tpQECHbUAKQ-1 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-3fe182913c5so142476695e9.0 for ; Mon, 02 Oct 2023 04:25:13 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1696245913; x=1696850713; h=content-transfer-encoding:in-reply-to:organization:from:references :cc:to:content-language:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=bOneOzTrSmpqtG0qhnCChNvIYEoW+1fDAEnSmXjPvzQ=; b=EhOapbbN5iH3aeZroaUhhmzQK5pqpGi5aWI2Cb6EyR+eAVr1rgexqmPVM2soV6S1Jy G7E6bOsjyXiacAhzdpP7YKr8uMIjOZUs//ovOGaUhScj1TDZCBJGW1Rw4nWmwnJXfwfy 4Wgwp+5XuOJy6v+zmfH6huXH+KNa/geRN/fQMWX473jZv+OyGJGlLGKGwq5PNq54Tkpc CJgO3vwPO1tpPOPHwBZG3dobCgxSyqDxhZAAyuMThtivxYQXfdms/T6Y9tp/ffftJusl F4v+YQECRnxFIaOmbPXjAbBkFj2jv1xaGzRfYRJm7ZncGEY9KK7xS0PpkjbTgeLJ2MZ9 ekBQ== X-Gm-Message-State: AOJu0Yxn4+uTyBU07X+ytZgyDCv1y8nBDx5dhFtousuSJfwOpSmJNYIn 2gI6NqPo1yzXz0BwGRxUtfInkbsDXBzRnsjzcvLsSiVVXmVCDACDaylNAIcC/zOH50vBF3Sb304 HlXEIhHy1eEM= X-Received: by 2002:a1c:7204:0:b0:405:2e28:4878 with SMTP id n4-20020a1c7204000000b004052e284878mr9305401wmc.30.1696245912666; Mon, 02 Oct 2023 04:25:12 -0700 (PDT) X-Google-Smtp-Source: AGHT+IH1f4UOW5e13WimBj1kblk64FdiBVm0BzOHx3wepByhk2+qhVS2Z3xsWgx8Ay1nWRlG8oCfxg== X-Received: by 2002:a1c:7204:0:b0:405:2e28:4878 with SMTP id n4-20020a1c7204000000b004052e284878mr9305375wmc.30.1696245912165; Mon, 02 Oct 2023 04:25:12 -0700 (PDT) Received: from ?IPV6:2003:cb:c735:f200:cb49:cb8f:88fc:9446? (p200300cbc735f200cb49cb8f88fc9446.dip0.t-ipconnect.de. [2003:cb:c735:f200:cb49:cb8f:88fc:9446]) by smtp.gmail.com with ESMTPSA id t9-20020a7bc3c9000000b003feae747ff2sm7016568wmj.35.2023.10.02.04.25.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Oct 2023 04:25:11 -0700 (PDT) Message-ID: <3057dab3-19f2-99ca-f125-e91a094975ed@redhat.com> Date: Mon, 2 Oct 2023 13:25:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH v4 2/2] mm: Init page count in reserve_bootmem_region when MEMINIT_EARLY To: Mike Rapoport Cc: Yajun Deng , akpm@linux-foundation.org, mike.kravetz@oracle.com, muchun.song@linux.dev, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20230928083302.386202-1-yajun.deng@linux.dev> <20230928083302.386202-3-yajun.deng@linux.dev> <20230929083018.GU3303@kernel.org> <20230929100252.GW3303@kernel.org> <15233624-f32e-172e-b2f6-7ca7bffbc96d@linux.dev> <20231001185934.GX3303@kernel.org> <90342474-432a-9fe3-2f11-915a04f0053f@linux.dev> <20231002084708.GZ3303@kernel.org> <20231002111051.GA3303@kernel.org> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20231002111051.GA3303@kernel.org> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: A2DB140005 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: uj7cugmouanj71ieyes8kcxabbi8kz16 X-HE-Tag: 1696245920-734533 X-HE-Meta: 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 17vn6B8i 3AUIgwB3dhDrf18OcS8h9xLZZ9uqfxdzL8/zbJiJQRCW8y3JrmWek7lKHkdmlg4sq8DTBUyxlGIpa9Zl2I+R+eNDfTnOuuVBo6kAMPBX83qTlXMcyDKNPKKftFWbCKzDmE7ywSNQLnzW61g1wU76iC5MLOLGNUsCozrhocHjWHzGuFn9JHgdmAPjMNtG4STZ34+htQk6sbahp+AUBn8HhyIeunxqGz/3wOh7FC1tfdHpISQT7zo/vq/zCU8Gv+lwAQVcrGuwhapuYQkbrfc2pzlzjkigdqjv4pIMvFCeyehRIC587D6H4ZNJqFLdoBfXHQ61GdHtc2aPdnFaHjK/vrW/JXaLOOjUGILFft8f1Wq9bN6ONe2MrOU9Q019AyiJcvlO3poTCGd01jb6sTAtX+D+aEcPWUbwE4Qkzct1Qwg6oUnA= 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 02.10.23 13:10, Mike Rapoport wrote: > On Mon, Oct 02, 2023 at 10:56:51AM +0200, David Hildenbrand wrote: >> On 02.10.23 10:47, Mike Rapoport wrote: >>> On Mon, Oct 02, 2023 at 03:03:56PM +0800, Yajun Deng wrote: >>>> >>>> On 2023/10/2 02:59, Mike Rapoport wrote: >>>>> On Fri, Sep 29, 2023 at 06:27:25PM +0800, Yajun Deng wrote: >>>>>> On 2023/9/29 18:02, Mike Rapoport wrote: >>>>>>>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>>>>>>>> index 06be8821d833..b868caabe8dc 100644 >>>>>>>>>> --- a/mm/page_alloc.c >>>>>>>>>> +++ b/mm/page_alloc.c >>>>>>>>>> @@ -1285,18 +1285,22 @@ void __free_pages_core(struct page *page, unsigned int order) >>>>>>>>>> unsigned int loop; >>>>>>>>>> /* >>>>>>>>>> - * When initializing the memmap, __init_single_page() sets the refcount >>>>>>>>>> - * of all pages to 1 ("allocated"/"not free"). We have to set the >>>>>>>>>> - * refcount of all involved pages to 0. >>>>>>>>>> + * When initializing the memmap, memmap_init_range sets the refcount >>>>>>>>>> + * of all pages to 1 ("reserved" and "free") in hotplug context. We >>>>>>>>>> + * have to set the refcount of all involved pages to 0. Otherwise, >>>>>>>>>> + * we don't do it, as reserve_bootmem_region only set the refcount on >>>>>>>>>> + * reserve region ("reserved") in early context. >>>>>>>>>> */ >>>>>>>>> Again, why hotplug and early init should be different? >>>>>>>> I will add a comment that describes it will save boot time. >>>>>>> But why do we need initialize struct pages differently at boot time vs >>>>>>> memory hotplug? >>>>>>> Is there a reason memory hotplug cannot have page count set to 0 just like >>>>>>> for pages reserved at boot time? >>>>>> This patch just save boot time in MEMINIT_EARLY. If someone finds out that >>>>>> it can save time in >>>>>> >>>>>> MEMINIT_HOTPLUG, I think it can be done in another patch later. I just >>>>>> keeping it in the same. >>>>> But it's not the same. It becomes slower after your patch and the code that >>>>> frees the pages for MEMINIT_EARLY and MEMINIT_HOTPLUG becomes non-uniform >>>>> for no apparent reason. >>>> >>>> __free_pages_core will also be called by others, such as: >>>> deferred_free_range, do_collection and memblock_free_late. >>>> >>>> We couldn't remove  'if (page_count(page))' even if we set page count to 0 >>>> when MEMINIT_HOTPLUG. >>> >>> That 'if' breaks the invariant that __free_pages_core is always called for >>> pages with initialized page count. Adding it may lead to subtle bugs and >>> random memory corruption so we don't want to add it at the first place. >> >> As long as we have to special-case memory hotplug, we know that we are >> always coming via generic_online_page() in that case. We could either move >> some logic over there, or let __free_pages_core() know what it should do. > > Looks like the patch rather special cases MEMINIT_EARLY, although I didn't > check throughfully other code paths. > Anyway, relying on page_count() to be correct in different ways for > different callers of __free_pages_core() does not sound right to me. Absolutely agreed. -- Cheers, David / dhildenb