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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BA990C2BA4C for ; Wed, 26 Jan 2022 14:36:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242206AbiAZOgx (ORCPT ); Wed, 26 Jan 2022 09:36:53 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:30682 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235530AbiAZOgw (ORCPT ); Wed, 26 Jan 2022 09:36:52 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1643207811; 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=KSCdq2HiaIlQL8PtJ4qbPosx+p7d/L8aRu/9I6dFWmQ=; b=Kd1dWi0Iq77VwJB/pEYAX3c5lcerKFGjscHSkfpercbWVZKn8U8J+3KwbJxusaZi5lPXjd 3HAcUYhXqDpjRZ+ZF5RapPsoW7ngUx0NHRw4nx4ZwHfIeeNr9Dk0u57Re9z4/vl5Vr51c8 mWli/WwAIgYVgcv1zb8S7333bC7Iq3s= 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=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-527-SaN36L_vOZKcsJWlpmuxcA-1; Wed, 26 Jan 2022 09:36:50 -0500 X-MC-Unique: SaN36L_vOZKcsJWlpmuxcA-1 Received: by mail-wm1-f72.google.com with SMTP id ay8-20020a05600c1e0800b00350de81da56so633836wmb.9 for ; Wed, 26 Jan 2022 06:36:45 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:organization:in-reply-to :content-transfer-encoding; bh=KSCdq2HiaIlQL8PtJ4qbPosx+p7d/L8aRu/9I6dFWmQ=; b=TLfzyvXpvE8riwCNi7RsYDahx6wu0DKup/lmNRRINpFoX5gTLI0JCEg2QH4SaX+g9q 4eaVknJhBPRh9NGG0EBF/z8Uz3EoeAljYDfaOnX87Y6cDtqT0efT1LZ9LRwC0pntSz8d kBE6/aG90HAUTg06DliCssVLR1UoZASJKVTDQPEO5JyU0wCckt57Hu81QtcJNhWVbDaa /tcQ3zh5zRNyqAI1XBw0A9yLJVKP9r9myWksJFvdgmlsaszal4b2uwSq/iG1QKoxCfWD a5MgiYdBIvZOT7DXgD+kV8aV7CySgfPuaPFS8jS8cmtwXV3H+xp0DHqg1RZsVn23zzCq GQig== X-Gm-Message-State: AOAM5301Bo0a5zeioAUx+yQkVcHNUXLxPjnh8Nrc1uhWPsfCJ8Xcpz3P jkqPHItoGyUIRvjwCAXynhdeoBzRTpimpu940Xeklpm8gjDmX2IafxAh/sCUVwP3lwxZlwJLlMb 8RK+c3hPZJtZS6HraTj3xtF4d X-Received: by 2002:a05:600c:3550:: with SMTP id i16mr7780944wmq.17.1643207804695; Wed, 26 Jan 2022 06:36:44 -0800 (PST) X-Google-Smtp-Source: ABdhPJyDZQP/GItwQ2iSU2jMAigVtCfjFz0ZQfMmT1SOvbAH3coXblDd/rStpTrddHx4KFzd916moA== X-Received: by 2002:a05:600c:3550:: with SMTP id i16mr7780918wmq.17.1643207804474; Wed, 26 Jan 2022 06:36:44 -0800 (PST) Received: from ?IPV6:2003:cb:c709:2700:cdd8:dcb0:2a69:8783? (p200300cbc7092700cdd8dcb02a698783.dip0.t-ipconnect.de. [2003:cb:c709:2700:cdd8:dcb0:2a69:8783]) by smtp.gmail.com with ESMTPSA id w8sm20054277wre.83.2022.01.26.06.36.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 26 Jan 2022 06:36:43 -0800 (PST) Message-ID: <683d7a13-70a5-6ba9-e290-9ac4db309535@redhat.com> Date: Wed, 26 Jan 2022 15:36:42 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [PATCH RFC v2 2/9] mm: optimize do_wp_page() for fresh pages in local LRU pagevecs Content-Language: en-US To: Matthew Wilcox Cc: linux-kernel@vger.kernel.org, Andrew Morton , Hugh Dickins , Linus Torvalds , David Rientjes , Shakeel Butt , John Hubbard , Jason Gunthorpe , Mike Kravetz , Mike Rapoport , Yang Shi , "Kirill A . Shutemov" , Vlastimil Babka , Jann Horn , Michal Hocko , Nadav Amit , Rik van Riel , Roman Gushchin , Andrea Arcangeli , Peter Xu , Donald Dutile , Christoph Hellwig , Oleg Nesterov , Jan Kara , Liang Zhang , linux-mm@kvack.org References: <20220126095557.32392-1-david@redhat.com> <20220126095557.32392-3-david@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26.01.22 15:31, Matthew Wilcox wrote: > On Wed, Jan 26, 2022 at 10:55:50AM +0100, David Hildenbrand wrote: >> diff --git a/mm/memory.c b/mm/memory.c >> index bcd3b7c50891..61d67ceef734 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -3298,7 +3298,17 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) >> * >> * PageKsm() doesn't necessarily raise the page refcount. >> */ >> - if (PageKsm(page) || page_count(page) > 1 + PageSwapCache(page)) >> + if (PageKsm(page)) >> + goto copy; >> + if (page_count(page) > 1 + PageSwapCache(page) + !PageLRU(page)) >> + goto copy; >> + if (!PageLRU(page)) >> + /* >> + * Note: We cannot easily detect+handle references from >> + * remote LRU pagevecs or references to PageLRU() pages. >> + */ >> + lru_add_drain(); >> + if (page_count(page) > 1 + PageSwapCache(page)) >> goto copy; > > I worry we're starting to get too accurate here. How about: > In that simplified case we'll essentially trylock_page() and for most pages that are ordinarily shared by e.g., 2 processes. > if (PageKsm(page) || page_count(page) > 3) > goto copy; > if (!PageLRU(page)) > lru_add_drain(); > if (!trylock_page(page)) > goto copy; > ... > I think we might at least want the if (page_count(page) > 1 + PageSwapCache(page)) goto copy; check here. >> if (!trylock_page(page)) >> goto copy; >> -- >> 2.34.1 >> > -- Thanks, David / dhildenb