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 0B914C433F5 for ; Thu, 24 Mar 2022 06:24:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 467CE6B0072; Thu, 24 Mar 2022 02:24:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 416E66B0073; Thu, 24 Mar 2022 02:24:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2DEB76B0074; Thu, 24 Mar 2022 02:24:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.25]) by kanga.kvack.org (Postfix) with ESMTP id 1E7046B0072 for ; Thu, 24 Mar 2022 02:24:53 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id DF7EE2C7 for ; Thu, 24 Mar 2022 06:24:52 +0000 (UTC) X-FDA: 79278291624.11.93DE735 Received: from mail-vk1-f178.google.com (mail-vk1-f178.google.com [209.85.221.178]) by imf09.hostedemail.com (Postfix) with ESMTP id 6332B140012 for ; Thu, 24 Mar 2022 06:24:52 +0000 (UTC) Received: by mail-vk1-f178.google.com with SMTP id d129so2032306vkh.13 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=veLWEPG7j7Pam5m8Ic5rg1qzNSK8e8X7QOwlMQ7Ip1UdTFCHep+L5/dWJ9Ud02wOKe Mw8p+MFCCnAR4LPG37LCU3wTfDlUup+iU8DUE0frh5yit8s5Q6IZ+XkSTH7dIs+39ky8 LQ6Pu2pX0+0aNHdYw1jJEYyMXG+RADC1uWr9xxO2J75gFL/lxfDZs+faxPH9DxbpdgLc 6GRo5JiVP5tUxoickXrPP/8TREfHHNiVuIjAPp6//rr7zFZJdDrtZCyr7KaeFIbjEgma vovcJWuTjnivqEbseohPjZxgYGoHrQGgtqB/ywtcdUp7SOgkJ8jH13xRwzo9BqDswMy1 uqGg== X-Gm-Message-State: AOAM5338NExBWfgyiJLqHovn1JloEcaPCz2N8jKSafJutl5x7IpRHTgM Rjb94vl2RKVVADmkgdgDWv2HZfn26JwOUBYoXzT6kw== 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" Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=b5W5RtOD; spf=pass (imf09.hostedemail.com: domain of yuzhao@google.com designates 209.85.221.178 as permitted sender) smtp.mailfrom=yuzhao@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 6332B140012 X-Stat-Signature: hh541z1i8f9refqpxs7hi6kzzajqoec5 X-HE-Tag: 1648103092-527088 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 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/