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 1EADCC433FE for ; Fri, 15 Apr 2022 02:23:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348647AbiDOCZv (ORCPT ); Thu, 14 Apr 2022 22:25:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57050 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239639AbiDOCZu (ORCPT ); Thu, 14 Apr 2022 22:25:50 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DE93D433A1; Thu, 14 Apr 2022 19:23:22 -0700 (PDT) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Kfg7F6cDXzgYSS; Fri, 15 Apr 2022 10:21:29 +0800 (CST) Received: from dggpemm500002.china.huawei.com (7.185.36.229) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 15 Apr 2022 10:23:20 +0800 Received: from [10.174.178.178] (10.174.178.178) by dggpemm500002.china.huawei.com (7.185.36.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 15 Apr 2022 10:23:18 +0800 Message-ID: <4c416f09-5304-07fd-cb53-5c9c8c75f6fa@huawei.com> Date: Fri, 15 Apr 2022 10:23:18 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.0.3 Subject: Re: [PATCH v10 06/14] mm: multi-gen LRU: minimal implementation To: Yu Zhao CC: Stephen Rothwell , , Andi Kleen , Andrew Morton , Aneesh Kumar , Barry Song <21cnbao@gmail.com>, Catalin Marinas , Dave Hansen , "Hillf Danton" , Jens Axboe , Jesse Barnes , Johannes Weiner , Jonathan Corbet , Linus Torvalds , "Matthew Wilcox" , Mel Gorman , Michael Larabel , Michal Hocko , Mike Rapoport , Rik van Riel , Vlastimil Babka , Will Deacon , Ying Huang , , , , , , 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 References: <20220407031525.2368067-1-yuzhao@google.com> <20220407031525.2368067-7-yuzhao@google.com> <71af92d2-0777-c318-67fb-8f7d52c800bb@huawei.com> From: Chen Wandun In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.178] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemm500002.china.huawei.com (7.185.36.229) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/4/15 4:53, Yu Zhao 写道: > On Thu, Apr 14, 2022 at 07:47:54PM +0800, Chen Wandun wrote: >> On 2022/4/7 11:15, Yu Zhao wrote: >>> +static void inc_min_seq(struct lruvec *lruvec) >>> +{ >>> + int type; >>> + struct lru_gen_struct *lrugen = &lruvec->lrugen; >>> + >>> + VM_BUG_ON(!seq_is_valid(lruvec)); >>> + >>> + for (type = 0; type < ANON_AND_FILE; type++) { >>> + if (get_nr_gens(lruvec, type) != MAX_NR_GENS) >>> + continue; >> I'm confused about relation between aging and LRU list operation. >> >> In function inc_max_seq,  both min_seq and max_seq will increase， >> the lrugen->lists[] indexed by lru_gen_from_seq(max_seq + 1) may >> be non-empty? > Yes. > >> for example, >> before inc_max_seq: >> min_seq == 0, lrugen->lists[0][type][zone] >> max_seq ==3, lrugen->lists[3][type][zone] >> >> after inc_max_seq: >> min_seq ==1, lrugen->lists[1][type][zone] >> max_seq ==4, lrugen->lists[0][type][zone] >> >> If lrugen->lists[0][type][zone] is not empty before inc_max_seq and it is >> the most inactive list，however lurgen->lists[0][type][zone] will become >> the most active list after inc_max_seq. > Correct. > >> So,  in this place, >> >> if (get_nr_gens(lruvec, type) != MAX_NR_GENS) >> continue; >> >> should change to >> >> if (get_nr_gens(lruvec, type) == MAX_NR_GENS) >> continue; > No, because max/min_seq will overlap if we do so. > > lrugen->lists[max_seq+1] can only be non-empty for anon LRU, for a > couple of reasons: > 1. We can't swap at all. > 2. Swapping is constrained, e.g., swapfile is full. > > Both cases are similar to a producer (the aging) overrunning a > consumer (the eviction). We used to handle them, but I simplified the > code because I don't feel they are worth handling [1]. Can lrugen->lists[max_seq+1]  also be non-empty for file LRU？ such as in dont reclaim mapped file page case(isolation will fail). If so, after aging, eviction will reclaim memory start from lrugen->lists[min_seq+1], but some oldest file page still remain in lrugen->lists[max_seq+1]. sort_folio can help to put misplaced pages to the right LRU list, but in this case, it does't help, because sort_folio only sort lrugen->lists[min_seq+1]. Thanks Wandun > > [1] https://lore.kernel.org/r/CAOUHufbDfwgm8PgCGkhCjbhMbm=fekfjgRR56NL-j+5iUGfVuw@mail.gmail.com/ > .