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 us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qLNpt-0043BW-2e for linux-arm-kernel@lists.infradead.org; Mon, 17 Jul 2023 13:00:24 +0000 Received: by mail-wr1-f69.google.com with SMTP id ffacd0b85a97d-2f2981b8364so2758732f8f.1 for ; Mon, 17 Jul 2023 06:00:10 -0700 (PDT) Message-ID: Date: Mon, 17 Jul 2023 15:00:07 +0200 MIME-Version: 1.0 Subject: Re: [PATCH v3 1/4] mm: Non-pmd-mappable, large folios for folio_add_new_anon_rmap() References: <20230714160407.4142030-1-ryan.roberts@arm.com> <20230714161733.4144503-1-ryan.roberts@arm.com> From: David Hildenbrand In-Reply-To: <20230714161733.4144503-1-ryan.roberts@arm.com> Content-Language: en-US List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+lwn-linux-arm-kernel=archive.lwn.net@lists.infradead.org List-Archive: To: Ryan Roberts , Andrew Morton , Matthew Wilcox , "Kirill A. Shutemov" , Yin Fengwei , Yu Zhao , Catalin Marinas , Will Deacon , Anshuman Khandual , Yang Shi , "Huang, Ying" , Zi Yan , Luis Chamberlain Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org On 14.07.23 18:17, Ryan Roberts wrote: > In preparation for FLEXIBLE_THP support, improve > folio_add_new_anon_rmap() to allow a non-pmd-mappable, large folio to be > passed to it. In this case, all contained pages are accounted using the > order-0 folio (or base page) scheme. > > Signed-off-by: Ryan Roberts > Reviewed-by: Yu Zhao > Reviewed-by: Yin Fengwei > --- > mm/rmap.c | 28 +++++++++++++++++++++------- > 1 file changed, 21 insertions(+), 7 deletions(-) > > diff --git a/mm/rmap.c b/mm/rmap.c > index 0c0d8857dfce..f293d072368a 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1278,31 +1278,45 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma, > * This means the inc-and-test can be bypassed. > * The folio does not have to be locked. > * > - * If the folio is large, it is accounted as a THP. As the folio > + * If the folio is pmd-mappable, it is accounted as a THP. As the folio > * is new, it's assumed to be mapped exclusively by a single process. > */ > void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma, > unsigned long address) > { > - int nr; > + int nr = folio_nr_pages(folio); > > - VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma); > + VM_BUG_ON_VMA(address < vma->vm_start || > + address + (nr << PAGE_SHIFT) > vma->vm_end, vma); > __folio_set_swapbacked(folio); > > - if (likely(!folio_test_pmd_mappable(folio))) { > + if (!folio_test_large(folio)) { Why remove the "likely" here? The patch itself does not change anything about that condition. > /* increment count (starts at -1) */ > atomic_set(&folio->_mapcount, 0); > - nr = 1; > + __page_set_anon_rmap(folio, &folio->page, vma, address, 1); > + } else if (!folio_test_pmd_mappable(folio)) { > + int i; > + > + for (i = 0; i < nr; i++) { > + struct page *page = folio_page(folio, i); > + > + /* increment count (starts at -1) */ > + atomic_set(&page->_mapcount, 0); > + __page_set_anon_rmap(folio, page, vma, > + address + (i << PAGE_SHIFT), 1); > + } > + > + /* increment count (starts at 0) */ That comment is a bit misleading. We're not talking about a mapcount as in the other cases here. > + atomic_set(&folio->_nr_pages_mapped, nr); > } else { > /* increment count (starts at -1) */ > atomic_set(&folio->_entire_mapcount, 0); > atomic_set(&folio->_nr_pages_mapped, COMPOUND_MAPPED); > - nr = folio_nr_pages(folio); > + __page_set_anon_rmap(folio, &folio->page, vma, address, 1); > __lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr); > } > Apart from that, LGTM. -- Cheers, David / dhildenb _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel