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 EBAB0C433F5 for ; Thu, 24 Mar 2022 06:24:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348174AbiCXG00 (ORCPT ); Thu, 24 Mar 2022 02:26:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57936 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242173AbiCXG0Y (ORCPT ); Thu, 24 Mar 2022 02:26:24 -0400 Received: from mail-vk1-xa2f.google.com (mail-vk1-xa2f.google.com [IPv6:2607:f8b0:4864:20::a2f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B917DEDA for ; Wed, 23 Mar 2022 23:24:52 -0700 (PDT) Received: by mail-vk1-xa2f.google.com with SMTP id w123so2046806vkg.7 for ; Wed, 23 Mar 2022 23:24:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=zGkLO8QE+JkINxXufCxF2QAgYC6g0Sy7UndvDKoQKoY=; b=b5W5RtODlUZwjxFNOLlgJKy1liQ7knXpgC6Q4PMKfK70IK3Z+SGPCLgekfc7YBtf6T RWnXoJ1DVG/iwdj8CxOvsG63VuHHFRBKgDx7YdCZil2CSFii61MsAk4craMFawUK1KKQ CzXcxF4PiKAjWUrnjLmou3WI+kpa5bOhbyd2Br+AmOkuCZmxvE8fh5aFWhanPGyUeM// VsQnaJ+jt3Ef6rh/nwOUmkbDyGl80bpLr0qPPjBNjHDjqWvv6RbGGNzQfUiuNSkxmoqO z8TwgnXmoPLO7QyTzR66ZAVZkmrjRKkgX3eioW4J9VQKr7lDL735TS1SM4RmJKTIQh4K L0mw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=zGkLO8QE+JkINxXufCxF2QAgYC6g0Sy7UndvDKoQKoY=; b=35Noctnx6p/In9Y9lTaMKp/7FFgb/1xuAHsnQiiEpzlUaRP+nD+bPsO7PmsiM1o5oj cedObpuczGMtOResjknRIE20pVMNm5Ph2YDyXUZZGSELkftlTmg7Oqqld7+CPDZoofzV XPZ/twrBq0nnGFE5aCUJ9FYShYcGxxKkZmNuRvbD4ndO1CojjQ0Qvz+DcpHIpAvYmWtj RZJW+5ys+BWwJK1Smev88TpA293/JWK/vaW74UjY4Sq1xnq8Doksxa48FMy3YLMVNWzm HTLmIryNY7Ee8UoIkbqnwYadjUhikWUv5vdNEuj2qlmZpa1gQUU21u8RDG254YgANjZx E0cw== X-Gm-Message-State: AOAM5318O4LsmpCMJG3G/qB9qpWVQnqo3WtzB8NPb92kYaQLwZfnJ8j8 pGjw0OjXQ7eqym5JVuxNX55PF8CYbAkDPD0BSxQD+A== X-Google-Smtp-Source: ABdhPJxRn6EidO34JgbBxOQGAq3o3F8SEptQ83Bk4g5oxbRMsM4MHsG6O9JwhGkK9BvQBDCzyAxmpAHbZjknr0b1eDI= X-Received: by 2002:a1f:a9cb:0:b0:33e:d145:85f0 with SMTP id s194-20020a1fa9cb000000b0033ed14585f0mr1848134vke.7.1648103091440; Wed, 23 Mar 2022 23:24:51 -0700 (PDT) MIME-Version: 1.0 References: <20220309021230.721028-1-yuzhao@google.com> <20220309021230.721028-7-yuzhao@google.com> In-Reply-To: From: Yu Zhao Date: Thu, 24 Mar 2022 00:24:40 -0600 Message-ID: Subject: Re: [PATCH v9 06/14] mm: multi-gen LRU: minimal implementation To: Barry Song <21cnbao@gmail.com> Cc: Andrew Morton , Linus Torvalds , Andi Kleen , Aneesh Kumar , Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Jesse Barnes , Johannes Weiner , Jonathan Corbet , Matthew Wilcox , Mel Gorman , Michael Larabel , Michal Hocko , Mike Rapoport , Rik van Riel , Vlastimil Babka , Will Deacon , Ying Huang , LAK , Linux Doc Mailing List , LKML , Linux-MM , Kernel Page Reclaim v2 , x86 , Brian Geffon , Jan Alexander Steffens , Oleksandr Natalenko , Steven Barrett , Suleiman Souhlal , Daniel Byrne , Donald Carr , =?UTF-8?Q?Holger_Hoffst=C3=A4tte?= , Konstantin Kharlamov , Shuang Zhai , Sofia Trinh , Vaibhav Jain Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 23, 2022 at 1:47 AM Barry Song <21cnbao@gmail.com> wrote: > > On Sat, Mar 19, 2022 at 4:11 PM Yu Zhao wrote: > > > > On Fri, Mar 18, 2022 at 9:01 PM Barry Song <21cnbao@gmail.com> wrote: > > > > > > > +static int folio_inc_gen(struct lruvec *lruvec, struct folio *folio, bool reclaiming) > > > > +{ > > > > + unsigned long old_flags, new_flags; > > > > + int type = folio_is_file_lru(folio); > > > > + struct lru_gen_struct *lrugen = &lruvec->lrugen; > > > > + int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); > > > > + > > > > + do { > > > > + new_flags = old_flags = READ_ONCE(folio->flags); > > > > + VM_BUG_ON_FOLIO(!(new_flags & LRU_GEN_MASK), folio); > > > > + > > > > + new_gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; > > > > + new_gen = (old_gen + 1) % MAX_NR_GENS; > > > > > > new_gen is assigned twice, i assume you mean > > > old_gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; > > > new_gen = (old_gen + 1) % MAX_NR_GENS; > > > > > > or do you always mean new_gen = lru_gen_from_seq(min_seq) + 1? > > > > Thanks a lot for your attention to details! > > > > The first line should be in the next patch but I overlooked during the > > last refactoring: > > Thanks for the clarification. So an unmapped file-backed page which is > accessed only by system call will always be in either min_seq or > min_seq + 1? it has no chance to be in max_seq like a faulted-in > mapped file page? That's right. The rationale is documented here under the `Assumptions` section [1]. This is also related to Aneesh's question about why MGLRU doesn't need additional heuristics for VM_EXEC pages [2]. Unmapped file pages weaken the protection of executable pages under heavy buffered IO workloads like Java NIO. [1] https://lore.kernel.org/linux-mm/20220309021230.721028-15-yuzhao@google.com/ [2] https://lore.kernel.org/linux-mm/CAOUHufYfpiGdLSdffvzDqaD5oYFG99oDJ2xgQd2Ph77OFR5NAA@mail.gmail.com/ 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 15F50C433EF for ; Thu, 24 Mar 2022 06:26:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=mitv4arfhl9ZFmk56zQwz6u+RhnchNaOnpv8Dufp3oo=; b=fYGlEASHe3LfTY 1GSGS/r/X4Dwctpuq4W3d97YXYZRhQx7M6Q7VV3sd1P1ftPAgccnRg6O6Df9GH4mcEnUFRG5KqBC/ eg9yrCjIxdgZHUN2TdUVa6tuXF9Y6PGQIpI4nlh8wh03pbyWEHo3IIdSU5GU1Fq90E2yWVVdxIS30 RijTwNeT5MI3paklhpRGB5Q5hoFvPqJ38FTtCau7sjKeA+NC4mmlLlFt4WSdDyqq6Ty/Nj4ulQAu3 jlfs/heEfbmIS/65+kjDjU0oRVEjU9iuH7ugq1/J/TvA23slPOzlfrFddwGQx9yDRQRSE6sWc2gOX muQz9TlHMdSPPRHMTs8Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nXGu3-00FpEO-Lx; Thu, 24 Mar 2022 06:24:59 +0000 Received: from mail-vk1-xa2d.google.com ([2607:f8b0:4864:20::a2d]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nXGu0-00FpCx-5O for linux-arm-kernel@lists.infradead.org; Thu, 24 Mar 2022 06:24:58 +0000 Received: by mail-vk1-xa2d.google.com with SMTP id j204so2044008vkj.8 for ; Wed, 23 Mar 2022 23:24:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=zGkLO8QE+JkINxXufCxF2QAgYC6g0Sy7UndvDKoQKoY=; b=b5W5RtODlUZwjxFNOLlgJKy1liQ7knXpgC6Q4PMKfK70IK3Z+SGPCLgekfc7YBtf6T RWnXoJ1DVG/iwdj8CxOvsG63VuHHFRBKgDx7YdCZil2CSFii61MsAk4craMFawUK1KKQ CzXcxF4PiKAjWUrnjLmou3WI+kpa5bOhbyd2Br+AmOkuCZmxvE8fh5aFWhanPGyUeM// VsQnaJ+jt3Ef6rh/nwOUmkbDyGl80bpLr0qPPjBNjHDjqWvv6RbGGNzQfUiuNSkxmoqO z8TwgnXmoPLO7QyTzR66ZAVZkmrjRKkgX3eioW4J9VQKr7lDL735TS1SM4RmJKTIQh4K L0mw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=zGkLO8QE+JkINxXufCxF2QAgYC6g0Sy7UndvDKoQKoY=; b=hGLGD3QJN8LahERlY35QqJZ95W9aZqdHftN19ZNc1yUoALXIxK+ksxu7g8Cm0jQiNB +LwTL+H0KJj7eAeJzBOvE8V5T9isI3eaxhRdon+5DVBQunkz8zc/8J3nw5K75WiyjxqF feLNdLMJaR0Uy0O9ztdgS/T0aNvff0xJRR8q0EsdUNVqhldDocIU2QlMh1zsrNTq5Iw6 fvBYrmYghjKTFj3Shrl1+ayCr+eqLo+LCsmqVEZxCTYycUWwNRWV2PIvyaaLyET/x6rq UbVxHYkjSIT/y76wZBSKYB6IiuC9aZ6Pv8BR9dyoYumiV8LgPEDbejwOCdA4Vk9zp6jM 8+Jg== X-Gm-Message-State: AOAM530MQwkZxSeAYyoJs8lGHAvMqYLjtL2vyT8GC4r2vShOxXw5x1lS 5oLu9rLiyUjCYEVuy/5bilNymxeqKfmyJO6gly6xRQ== X-Google-Smtp-Source: ABdhPJxRn6EidO34JgbBxOQGAq3o3F8SEptQ83Bk4g5oxbRMsM4MHsG6O9JwhGkK9BvQBDCzyAxmpAHbZjknr0b1eDI= X-Received: by 2002:a1f:a9cb:0:b0:33e:d145:85f0 with SMTP id s194-20020a1fa9cb000000b0033ed14585f0mr1848134vke.7.1648103091440; Wed, 23 Mar 2022 23:24:51 -0700 (PDT) MIME-Version: 1.0 References: <20220309021230.721028-1-yuzhao@google.com> <20220309021230.721028-7-yuzhao@google.com> In-Reply-To: From: Yu Zhao Date: Thu, 24 Mar 2022 00:24:40 -0600 Message-ID: Subject: Re: [PATCH v9 06/14] mm: multi-gen LRU: minimal implementation To: Barry Song <21cnbao@gmail.com> Cc: Andrew Morton , Linus Torvalds , Andi Kleen , Aneesh Kumar , Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Jesse Barnes , Johannes Weiner , Jonathan Corbet , Matthew Wilcox , Mel Gorman , Michael Larabel , Michal Hocko , Mike Rapoport , Rik van Riel , Vlastimil Babka , Will Deacon , Ying Huang , LAK , Linux Doc Mailing List , LKML , Linux-MM , Kernel Page Reclaim v2 , x86 , Brian Geffon , Jan Alexander Steffens , Oleksandr Natalenko , Steven Barrett , Suleiman Souhlal , Daniel Byrne , Donald Carr , =?UTF-8?Q?Holger_Hoffst=C3=A4tte?= , Konstantin Kharlamov , Shuang Zhai , Sofia Trinh , Vaibhav Jain X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220323_232456_212394_4AD516DF X-CRM114-Status: GOOD ( 23.22 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Mar 23, 2022 at 1:47 AM Barry Song <21cnbao@gmail.com> wrote: > > On Sat, Mar 19, 2022 at 4:11 PM Yu Zhao wrote: > > > > On Fri, Mar 18, 2022 at 9:01 PM Barry Song <21cnbao@gmail.com> wrote: > > > > > > > +static int folio_inc_gen(struct lruvec *lruvec, struct folio *folio, bool reclaiming) > > > > +{ > > > > + unsigned long old_flags, new_flags; > > > > + int type = folio_is_file_lru(folio); > > > > + struct lru_gen_struct *lrugen = &lruvec->lrugen; > > > > + int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); > > > > + > > > > + do { > > > > + new_flags = old_flags = READ_ONCE(folio->flags); > > > > + VM_BUG_ON_FOLIO(!(new_flags & LRU_GEN_MASK), folio); > > > > + > > > > + new_gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; > > > > + new_gen = (old_gen + 1) % MAX_NR_GENS; > > > > > > new_gen is assigned twice, i assume you mean > > > old_gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; > > > new_gen = (old_gen + 1) % MAX_NR_GENS; > > > > > > or do you always mean new_gen = lru_gen_from_seq(min_seq) + 1? > > > > Thanks a lot for your attention to details! > > > > The first line should be in the next patch but I overlooked during the > > last refactoring: > > Thanks for the clarification. So an unmapped file-backed page which is > accessed only by system call will always be in either min_seq or > min_seq + 1? it has no chance to be in max_seq like a faulted-in > mapped file page? That's right. The rationale is documented here under the `Assumptions` section [1]. This is also related to Aneesh's question about why MGLRU doesn't need additional heuristics for VM_EXEC pages [2]. Unmapped file pages weaken the protection of executable pages under heavy buffered IO workloads like Java NIO. [1] https://lore.kernel.org/linux-mm/20220309021230.721028-15-yuzhao@google.com/ [2] https://lore.kernel.org/linux-mm/CAOUHufYfpiGdLSdffvzDqaD5oYFG99oDJ2xgQd2Ph77OFR5NAA@mail.gmail.com/ _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel