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 69A9AC001DF for ; Tue, 18 Jul 2023 09:52:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232375AbjGRJvj (ORCPT ); Tue, 18 Jul 2023 05:51:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48030 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232008AbjGRJvI (ORCPT ); Tue, 18 Jul 2023 05:51:08 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 37C82F1 for ; Tue, 18 Jul 2023 02:51:07 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 712612F4; Tue, 18 Jul 2023 02:51:50 -0700 (PDT) Received: from [10.1.34.52] (C02Z41KALVDN.cambridge.arm.com [10.1.34.52]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 880953F67D; Tue, 18 Jul 2023 02:51:05 -0700 (PDT) Message-ID: Date: Tue, 18 Jul 2023 10:51:04 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v1 2/3] mm: Implement folio_remove_rmap_range() To: "Huang, Ying" Cc: Andrew Morton , Matthew Wilcox , Yin Fengwei , David Hildenbrand , Yu Zhao , Yang Shi , Zi Yan , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20230717143110.260162-1-ryan.roberts@arm.com> <20230717143110.260162-3-ryan.roberts@arm.com> <874jm1d9ic.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Ryan Roberts In-Reply-To: <874jm1d9ic.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18/07/2023 07:22, Huang, Ying wrote: > Ryan Roberts writes: > >> Like page_remove_rmap() but batch-removes the rmap for a range of pages >> belonging to a folio. This can provide a small speedup due to less >> manipuation of the various counters. But more crucially, if removing the >> rmap for all pages of a folio in a batch, there is no need to >> (spuriously) add it to the deferred split list, which saves significant >> cost when there is contention for the split queue lock. >> >> All contained pages are accounted using the order-0 folio (or base page) >> scheme. >> >> Signed-off-by: Ryan Roberts >> --- >> include/linux/rmap.h | 2 ++ >> mm/rmap.c | 65 ++++++++++++++++++++++++++++++++++++++++++++ >> 2 files changed, 67 insertions(+) >> >> diff --git a/include/linux/rmap.h b/include/linux/rmap.h >> index b87d01660412..f578975c12c0 100644 >> --- a/include/linux/rmap.h >> +++ b/include/linux/rmap.h >> @@ -200,6 +200,8 @@ void page_add_file_rmap(struct page *, struct vm_area_struct *, >> bool compound); >> void page_remove_rmap(struct page *, struct vm_area_struct *, >> bool compound); >> +void folio_remove_rmap_range(struct folio *folio, struct page *page, >> + int nr, struct vm_area_struct *vma); >> >> void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *, >> unsigned long address, rmap_t flags); >> diff --git a/mm/rmap.c b/mm/rmap.c >> index 2baf57d65c23..1da05aca2bb1 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -1359,6 +1359,71 @@ void page_add_file_rmap(struct page *page, struct vm_area_struct *vma, >> mlock_vma_folio(folio, vma, compound); >> } >> >> +/* >> + * folio_remove_rmap_range - take down pte mappings from a range of pages >> + * belonging to a folio. All pages are accounted as small pages. >> + * @folio: folio that all pages belong to >> + * @page: first page in range to remove mapping from >> + * @nr: number of pages in range to remove mapping from >> + * @vma: the vm area from which the mapping is removed >> + * >> + * The caller needs to hold the pte lock. >> + */ >> +void folio_remove_rmap_range(struct folio *folio, struct page *page, >> + int nr, struct vm_area_struct *vma) >> +{ >> + atomic_t *mapped = &folio->_nr_pages_mapped; >> + int nr_unmapped = 0; >> + int nr_mapped; >> + bool last; >> + enum node_stat_item idx; >> + >> + if (unlikely(folio_test_hugetlb(folio))) { >> + VM_WARN_ON_FOLIO(1, folio); >> + return; >> + } >> + >> + if (!folio_test_large(folio)) { >> + /* Is this the page's last map to be removed? */ >> + last = atomic_add_negative(-1, &page->_mapcount); >> + nr_unmapped = last; >> + } else { >> + for (; nr != 0; nr--, page++) { >> + /* Is this the page's last map to be removed? */ >> + last = atomic_add_negative(-1, &page->_mapcount); >> + if (last) { >> + /* Page still mapped if folio mapped entirely */ >> + nr_mapped = atomic_dec_return_relaxed(mapped); >> + if (nr_mapped < COMPOUND_MAPPED) >> + nr_unmapped++; >> + } >> + } >> + } >> + >> + if (nr_unmapped) { >> + idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED; >> + __lruvec_stat_mod_folio(folio, idx, -nr_unmapped); >> + >> + /* >> + * Queue anon THP for deferred split if we have just unmapped at > > Just some nitpicks. So feel free to ignore. > > s/anon THP/large folio/ ? ACK > >> + * least 1 page, while at least 1 page remains mapped. >> + */ >> + if (folio_test_large(folio) && folio_test_anon(folio)) >> + if (nr_mapped) > > if (folio_test_large(folio) && folio_test_anon(folio) && nr_mapped) ? ACK : I'll make these changes for the next version. > >> + deferred_split_folio(folio); >> + } >> + >> + /* >> + * It would be tidy to reset folio_test_anon mapping when fully >> + * unmapped, but that might overwrite a racing page_add_anon_rmap >> + * which increments mapcount after us but sets mapping before us: >> + * so leave the reset to free_pages_prepare, and remember that >> + * it's only reliable while mapped. >> + */ >> + >> + munlock_vma_folio(folio, vma, false); >> +} >> + >> /** >> * page_remove_rmap - take down pte mapping from a page >> * @page: page to remove mapping from > > Best Regards, > Huang, Ying