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 77A8DC4332F for ; Fri, 15 Apr 2022 06:31:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0F1226B0073; Fri, 15 Apr 2022 02:31:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0A00C6B0074; Fri, 15 Apr 2022 02:31:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E5B5B6B0075; Fri, 15 Apr 2022 02:31:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.27]) by kanga.kvack.org (Postfix) with ESMTP id D7FD46B0073 for ; Fri, 15 Apr 2022 02:31:45 -0400 (EDT) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id BC6C426A88 for ; Fri, 15 Apr 2022 06:31:45 +0000 (UTC) X-FDA: 79358142570.22.6C26022 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by imf18.hostedemail.com (Postfix) with ESMTP id 2A99C1C0006 for ; Fri, 15 Apr 2022 06:31:43 +0000 (UTC) Received: from dggpemm500023.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Kfmd60fpyzFpXP; Fri, 15 Apr 2022 14:29:14 +0800 (CST) Received: from dggpemm500002.china.huawei.com (7.185.36.229) by dggpemm500023.china.huawei.com (7.185.36.83) 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 14:31:40 +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 14:31:37 +0800 Message-ID: <9e3ca922-1448-2eb1-b056-218236e7c72f@huawei.com> Date: Fri, 15 Apr 2022 14:31:37 +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> <4c416f09-5304-07fd-cb53-5c9c8c75f6fa@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: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500002.china.huawei.com (7.185.36.229) X-CFilter-Loop: Reflected X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 2A99C1C0006 X-Stat-Signature: cm881ir44wnjcasdiso55h4e9apuzgjb Authentication-Results: imf18.hostedemail.com; dkim=none; spf=pass (imf18.hostedemail.com: domain of chenwandun@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=chenwandun@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-HE-Tag: 1650004303-564977 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: 在 2022/4/15 13:25, Yu Zhao 写道: > On Fri, Apr 15, 2022 at 10:23:18AM +0800, Chen Wandun wrote: >> 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？ > On reclaim path, no. But it can be forced to do so via debugfs. > >> such as in dont reclaim mapped file page case(isolation will fail). > You mean may_unmap=false? Pages stays in the same generation if > isolation fails. So lrugen->lists[min_seq] won't be empty in this > case. > >> 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]. > On reclaim path, inc_max_seq() is only called when need_aging=true, > and this guarantees max_seq-min_seq[LRU_GEN_FILE]+1 < MAX_NR_GENS. yes, I think so, but I did't find the logical in function get_nr_evictable, or am I missing something         if (min_seq[LRU_GEN_FILE] + MIN_NR_GENS > max_seq)                 *need_aging = true;         else if (min_seq[LRU_GEN_FILE] + MIN_NR_GENS < max_seq)                 *need_aging = false;         else if (young * MIN_NR_GENS > total)                 *need_aging = true;         else if (old * (MIN_NR_GENS + 2) < total)                 *need_aging = true;         else                 *need_aging = false; Thanks > .