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 36AFEC6FA8F for ; Wed, 30 Aug 2023 19:18:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239856AbjH3TS4 (ORCPT ); Wed, 30 Aug 2023 15:18:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56336 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242816AbjH3JqD (ORCPT ); Wed, 30 Aug 2023 05:46:03 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2D82B1A1 for ; Wed, 30 Aug 2023 02:46:00 -0700 (PDT) Received: from dggpemm100001.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4RbK9c1SJJzVkMY; Wed, 30 Aug 2023 17:43:32 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemm100001.china.huawei.com (7.185.36.93) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Wed, 30 Aug 2023 17:45:58 +0800 Message-ID: <646b619b-470a-40eb-bee9-85c7bd4c8a54@huawei.com> Date: Wed, 30 Aug 2023 17:45:57 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/8] mm: migrate: use a folio in migrate_misplaced_page() Content-Language: en-US To: Matthew Wilcox , "Huang, Ying" CC: Zi Yan , Andrew Morton , , , , Mike Kravetz , References: <20230821115624.158759-1-wangkefeng.wang@huawei.com> <20230821115624.158759-5-wangkefeng.wang@huawei.com> <855536BE-766C-49B2-B358-6C0548760929@nvidia.com> <875y4y65b8.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Kefeng Wang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpemm100001.china.huawei.com (7.185.36.93) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/8/29 10:10, Matthew Wilcox wrote: > On Tue, Aug 29, 2023 at 08:49:31AM +0800, Huang, Ying wrote: >> Zi Yan writes: >> >>> On 21 Aug 2023, at 7:56, Kefeng Wang wrote: >>> >>>> Use a folio in migrate_misplaced_page() to save compound_head() calls. >>>> >>>> Signed-off-by: Kefeng Wang >>>> --- >>>> mm/migrate.c | 23 ++++++++++++----------- >>>> 1 file changed, 12 insertions(+), 11 deletions(-) >>> >>> LGTM. And a comment below. Reveiwed-by: Zi Yan >>> >>>> >>>> diff --git a/mm/migrate.c b/mm/migrate.c >>>> index 281eafdf8e63..fc728f9a383f 100644 >>>> --- a/mm/migrate.c >>>> +++ b/mm/migrate.c >>>> @@ -2521,17 +2521,18 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma, >>>> int node) >>>> { >>>> pg_data_t *pgdat = NODE_DATA(node); >>>> + struct folio *folio = page_folio(page); >>>> int isolated; >>>> int nr_remaining; >>>> unsigned int nr_succeeded; >>>> LIST_HEAD(migratepages); >>>> - int nr_pages = thp_nr_pages(page); >>>> + int nr_pages = folio_nr_pages(folio); >>>> >>>> /* >>>> * Don't migrate file pages that are mapped in multiple processes >>>> * with execute permissions as they are probably shared libraries. >>>> */ >>>> - if (page_mapcount(page) != 1 && page_is_file_lru(page) && >>>> + if (page_mapcount(page) != 1 && folio_is_file_lru(folio) && >>> >>> page_mapcount() is not converted, since folio_mapcount() is not equivalent >>> to page_mapcount(). It can be converted and this function can be converted >>> to migrate_misplaced_folio() once we have something like folio_num_sharers(). >> >> It seems that we can use folio_estimated_sharers() here. > > So, funny thing, page_mapcount() was always wrong here. We have two > callers, do_huge_pmd_numa_page() and do_numa_page(). do_numa_page() > has a check for PageCompound() (and /* TODO: handle PTE-mapped THP */). > do_huge_pmd_numa_page() returns pfn_to_page(), after it got the pfn > fromm pmd_pfn(pmd). for PMD-mapped page，do_huge_pmd_numa_page() return head page unsigned long haddr = vmf->address & HPAGE_PMD_MASK; page = vm_normal_page_pmd(vma, haddr, pmd); do_numa_page() only handle base page with PageCompound() check， so we could use folio_estimated_sharers()， I am not clear why page_mapcount is wrong here, could you explain more, thank. > > That makes folio_estimated_sharers() an improvement, possibly even > a bugfix. Also, we should look at removing the PageCompound() check > in do_numa_page(). Yes, for pte-mapped thp and the large folio numa migrate support, we need remove the check, we could do it in another patchset. > >