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 A7108EB64DC for ; Mon, 17 Jul 2023 13:21:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 459EA6B0072; Mon, 17 Jul 2023 09:21:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 40A236B0074; Mon, 17 Jul 2023 09:21:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2D2A18D0001; Mon, 17 Jul 2023 09:21:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 1ABD96B0072 for ; Mon, 17 Jul 2023 09:21:40 -0400 (EDT) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id BB59FA0311 for ; Mon, 17 Jul 2023 13:21:39 +0000 (UTC) X-FDA: 81021165918.16.7C95711 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf27.hostedemail.com (Postfix) with ESMTP id E51CB4000B for ; Mon, 17 Jul 2023 13:21:37 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf27.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1689600098; a=rsa-sha256; cv=none; b=jDOgWzLFeNJ1qL5IMXR2osO1tjZvPxDIXQO806BsDKftogfEK+IPVE9rRjXF3LpZrrexHx hSeCyNH5BHAL4mbbQA1a0417HbNoCDs2FfXhGc/2j1JltSiNUu+sptrJr+yPw7uNYhH7rw hHBdmgaUkzkneNh4YVaZt0srWg3IeZM= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf27.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1689600098; 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; bh=DU7wQAlGlT9sp3pwFnA0EgF4NvbWeCA+4zVLaloXP1s=; b=Vf8lvAzHaSo8b+fHowR7o8xZcTZW9oOQHNjw5HqXeoMhwf9Dw2rOzpzzgeMNMdHzZDKPaz D8IQfPwhjFUPZ5AtQDqHVS1hAmj2PFehOA128iJkxYeFCGRU7gXfc/xGDXc4fBxTyNEwz8 BR+O2CrmAMyg5Vzv7kNQKi/+AUkF7nU= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4D12BC15; Mon, 17 Jul 2023 06:22:20 -0700 (PDT) Received: from [10.57.76.30] (unknown [10.57.76.30]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EA5323F67D; Mon, 17 Jul 2023 06:21:33 -0700 (PDT) Message-ID: Date: Mon, 17 Jul 2023 14:21:31 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v3 1/4] mm: Non-pmd-mappable, large folios for folio_add_new_anon_rmap() To: David Hildenbrand , Andrew Morton , Matthew Wilcox , "Kirill A. Shutemov" , Yin Fengwei , Yu Zhao , Catalin Marinas , Will Deacon , Anshuman Khandual , Yang Shi , "Huang, Ying" , Zi Yan , Luis Chamberlain Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20230714160407.4142030-1-ryan.roberts@arm.com> <20230714161733.4144503-1-ryan.roberts@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: E51CB4000B X-Stat-Signature: 6gfoimfhzi43efapsznz7abp9ni6gyu4 X-Rspam-User: X-HE-Tag: 1689600097-148347 X-HE-Meta: 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 IKL4OV7L eLwkymw39KBKhFhzOggYOR0FuZ/Bq91aW0QMFDuuikR9A6iSqgTJ9+RInQOsQZimHYTBe6/xAEyfUUIFMAVp2oc9j3/uhQ/AImUj+iXvmDZ8d3mTSI51pm3e13rz7wiFOH/Q6TF8IbJ0X+D1YbDSw+WU5zp3ksA44B+wifOc+kU5NkxMYkbUKE7rwJPO4DYiMSakbUp+KdemnBm0xRACDjdgIMSoB99B3A6/ped4pJFTZwtwmQOhAibFXuz24CB3m5xkdqcYEYbq2Iic= 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 17/07/2023 14:19, David Hildenbrand wrote: > On 17.07.23 15:13, Ryan Roberts wrote: >> On 17/07/2023 14:00, David Hildenbrand wrote: >>> On 14.07.23 18:17, Ryan Roberts wrote: >>>> In preparation for FLEXIBLE_THP support, improve >>>> folio_add_new_anon_rmap() to allow a non-pmd-mappable, large folio to be >>>> passed to it. In this case, all contained pages are accounted using the >>>> order-0 folio (or base page) scheme. >>>> >>>> Signed-off-by: Ryan Roberts >>>> Reviewed-by: Yu Zhao >>>> Reviewed-by: Yin Fengwei >>>> --- >>>>    mm/rmap.c | 28 +++++++++++++++++++++------- >>>>    1 file changed, 21 insertions(+), 7 deletions(-) >>>> >>>> diff --git a/mm/rmap.c b/mm/rmap.c >>>> index 0c0d8857dfce..f293d072368a 100644 >>>> --- a/mm/rmap.c >>>> +++ b/mm/rmap.c >>>> @@ -1278,31 +1278,45 @@ void page_add_anon_rmap(struct page *page, struct >>>> vm_area_struct *vma, >>>>     * This means the inc-and-test can be bypassed. >>>>     * The folio does not have to be locked. >>>>     * >>>> - * If the folio is large, it is accounted as a THP.  As the folio >>>> + * If the folio is pmd-mappable, it is accounted as a THP.  As the folio >>>>     * is new, it's assumed to be mapped exclusively by a single process. >>>>     */ >>>>    void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct >>>> *vma, >>>>            unsigned long address) >>>>    { >>>> -    int nr; >>>> +    int nr = folio_nr_pages(folio); >>>> >>>> -    VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma); >>>> +    VM_BUG_ON_VMA(address < vma->vm_start || >>>> +            address + (nr << PAGE_SHIFT) > vma->vm_end, vma); >>>>        __folio_set_swapbacked(folio); >>>> >>>> -    if (likely(!folio_test_pmd_mappable(folio))) { >>>> +    if (!folio_test_large(folio)) { >>> >>> Why remove the "likely" here? The patch itself does not change anything about >>> that condition. >> >> Good question; I'm not sure why. Will have to put it down to bad copy/paste >> fixup. Will put it back in the next version. >> >>> >>>>            /* increment count (starts at -1) */ >>>>            atomic_set(&folio->_mapcount, 0); >>>> -        nr = 1; >>>> +        __page_set_anon_rmap(folio, &folio->page, vma, address, 1); >>>> +    } else if (!folio_test_pmd_mappable(folio)) { >>>> +        int i; >>>> + >>>> +        for (i = 0; i < nr; i++) { >>>> +            struct page *page = folio_page(folio, i); >>>> + >>>> +            /* increment count (starts at -1) */ >>>> +            atomic_set(&page->_mapcount, 0); >>>> +            __page_set_anon_rmap(folio, page, vma, >>>> +                    address + (i << PAGE_SHIFT), 1); >>>> +        } >>>> + >>>> +        /* increment count (starts at 0) */ >>> >>> That comment is a bit misleading. We're not talking about a mapcount as in the >>> other cases here. >> >> Correct, I'm talking about _nr_pages_mapped, which starts 0, not -1 like >> _mapcount. The comment was intended to be in the style used in other similar >> places in rmap.c. I could change it to: "_nr_pages_mapped is 0-based, so set it >> to the number of pages in the folio" or remove it entirely? What do you prefer? >> > > We only have to comment what's weird, not what's normal. > > IOW, we also didn't have such a comment in the existing code when doing > atomic_set(&folio->_nr_pages_mapped, COMPOUND_MAPPED); > > > What might make sense here is a simple > > "All pages of the folio are PTE-mapped." > ACK - thanks.