From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ryan Roberts Subject: Re: [PATCH v1 04/10] mm: Implement folio_add_new_anon_rmap_range() Date: Wed, 28 Jun 2023 12:09:07 +0100 Message-ID: References: <20230626171430.3167004-1-ryan.roberts@arm.com> <20230626171430.3167004-5-ryan.roberts@arm.com> <8c01486f-3c1a-e50d-544e-502eadbddf05@intel.com> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <8c01486f-3c1a-e50d-544e-502eadbddf05@intel.com> List-ID: Content-Type: text/plain; charset="windows-1252" To: Yin Fengwei , Yu Zhao Cc: Andrew Morton , "Matthew Wilcox (Oracle)" , "Kirill A. Shutemov" , David Hildenbrand , Catalin Marinas , Will Deacon , Geert Uytterhoeven , Christian Borntraeger , Sven Schnelle , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-s390@vger.kernel.org On 28/06/2023 03:20, Yin Fengwei wrote: >=20 >=20 > On 6/27/23 16:09, Ryan Roberts wrote: >> On 27/06/2023 08:08, Yu Zhao wrote: >>> On Mon, Jun 26, 2023 at 11:14=E2=80=AFAM Ryan Roberts wrote: >>>> >>>> Like folio_add_new_anon_rmap() but batch-rmaps a range of pages >>>> belonging to a folio, for effciency savings. All pages are accounted as >>>> small pages. >>>> >>>> Signed-off-by: Ryan Roberts >>>> --- >>>> include/linux/rmap.h | 2 ++ >>>> mm/rmap.c | 43 +++++++++++++++++++++++++++++++++++++++++++ >>>> 2 files changed, 45 insertions(+) >>>> >>>> diff --git a/include/linux/rmap.h b/include/linux/rmap.h >>>> index a3825ce81102..15433a3d0cbf 100644 >>>> --- a/include/linux/rmap.h >>>> +++ b/include/linux/rmap.h >>>> @@ -196,6 +196,8 @@ void page_add_new_anon_rmap(struct page *, struct = vm_area_struct *, >>>> unsigned long address); >>>> void folio_add_new_anon_rmap(struct folio *, struct vm_area_struct *, >>>> unsigned long address); >>>> +void folio_add_new_anon_rmap_range(struct folio *folio, struct page *= page, >>>> + int nr, struct vm_area_struct *vma, unsigned long addr= ess); >>> >>> We should update folio_add_new_anon_rmap() to support large() && >>> !folio_test_pmd_mappable() folios instead. >>> >>> I double checked all places currently using folio_add_new_anon_rmap(), >>> and as expected, none actually allocates large() && >>> !folio_test_pmd_mappable() and maps it one by one, which makes the >>> cases simpler, i.e., >>> if (!large()) >>> // the existing basepage case >>> else if (!folio_test_pmd_mappable()) >>> // our new case >>> else >>> // the existing THP case >> >> I don't have a strong opinion either way. Happy to go with this suggesti= on. But >> the reason I did it as a new function was because I was following the pa= ttern in >> [1] which adds a new folio_add_file_rmap_range() function. >> >> [1] https://lore.kernel.org/linux-mm/20230315051444.3229621-35-willy@inf= radead.org/ > Oh. There is different here: > For page cache, large folio could be created by previous file access. But= later > file access by other process just need map partial large folio. In this c= ase, we need > _range for filemap. >=20 > But for anonymous, I suppose we always map whole folio in. So I agree wit= h Yu. We > don't need _range for folio_add_new_anon_rmap(). Thanks. Yes that makes sense - thanks. I'll merge the new case into folio_add_new_anon_rmap() for v2. >=20 >=20 > Regards > Yin, Fengwei >=20 >> >> >>> >>>> void page_add_file_rmap(struct page *, struct vm_area_struct *, >>>> bool compound); >>>> void folio_add_file_rmap_range(struct folio *, struct page *, unsigne= d int nr, >>>> diff --git a/mm/rmap.c b/mm/rmap.c >>>> index 1d8369549424..4050bcea7ae7 100644 >>>> --- a/mm/rmap.c >>>> +++ b/mm/rmap.c >>>> @@ -1305,6 +1305,49 @@ void folio_add_new_anon_rmap(struct folio *foli= o, struct vm_area_struct *vma, >>>> __page_set_anon_rmap(folio, &folio->page, vma, address, 1); >>>> } >>>> >>>> +/** >>>> + * folio_add_new_anon_rmap_range - Add mapping to a set of pages with= in a new >>>> + * anonymous potentially large folio. >>>> + * @folio: The folio containing the pages to be mapped >>>> + * @page: First page in the folio to be mapped >>>> + * @nr: Number of pages to be mapped >>>> + * @vma: the vm area in which the mapping is added >>>> + * @address: the user virtual address of the first page to be mapp= ed >>>> + * >>>> + * Like folio_add_new_anon_rmap() but batch-maps a range of pages wit= hin a folio >>>> + * using non-THP accounting. Like folio_add_new_anon_rmap(), the inc-= and-test is >>>> + * bypassed and the folio does not have to be locked. All pages in th= e folio are >>>> + * individually accounted. >>>> + * >>>> + * As the folio is new, it's assumed to be mapped exclusively by a si= ngle >>>> + * process. >>>> + */ >>>> +void folio_add_new_anon_rmap_range(struct folio *folio, struct page *= page, >>>> + int nr, struct vm_area_struct *vma, unsigned long addr= ess) >>>> +{ >>>> + int i; >>>> + >>>> + VM_BUG_ON_VMA(address < vma->vm_start || >>>> + address + (nr << PAGE_SHIFT) > vma->vm_end, vma); >>> >>> BTW, VM_BUG_ON* shouldn't be used in new code: >>> Documentation/process/coding-style.rst >> >> Thanks, sorry about that. Was copy-pasting from folio_add_new_anon_rmap(= ). >>