From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yin Fengwei Subject: Re: [PATCH v1 04/10] mm: Implement folio_add_new_anon_rmap_range() Date: Wed, 28 Jun 2023 10:20:43 +0800 Message-ID: <8c01486f-3c1a-e50d-544e-502eadbddf05@intel.com> References: <20230626171430.3167004-1-ryan.roberts@arm.com> <20230626171430.3167004-5-ryan.roberts@arm.com> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1687918868; x=1719454868; h=message-id:date:subject:to:cc:references:from: in-reply-to:content-transfer-encoding:mime-version; bh=8N+GO04oUUb9Vu0V3+FhmDkPsBK0sdwhgnaJBb29+Kk=; b=I8bPvY/q8aDkcUSrJbt8+PDJyfqFSyZ01XGvHokz+rutSIojtBzTQIAf bsaDxgBrgHiz8Uy1i0+mUgQD7YjToKluyY3bKRwadbD0KT6MRjogge18h ZJk/l08Ehc65hN5rrv9uBtD0QvvbRIiD3IZnrC8F/WONUQHQSj9rztZIZ DWmEbWJJ9xqQHImKB5DJirfFzdN4I6aHegrkPOLpBRAA3CBSAxSNwWJuN FRUhuk5NkqZ48eldqcH9g/h1etMs6M5aWc5WXo0ZENSBpql5lBP47JPoJ xVDi3a/nEvuOQlxmBWyHUfKqeQH7dCRosi91oMx0I0OQ0f0o6UY7H4z7L w==; Content-Language: en-US In-Reply-To: List-ID: Content-Type: text/plain; charset="windows-1252" To: Ryan Roberts , 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 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 v= m_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 *p= age, >>> + int nr, struct vm_area_struct *vma, unsigned long addre= ss); >> >> 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 >=20 > I don't have a strong opinion either way. Happy to go with this suggestio= n. But > the reason I did it as a new function was because I was following the pat= tern in > [1] which adds a new folio_add_file_rmap_range() function. >=20 > [1] https://lore.kernel.org/linux-mm/20230315051444.3229621-35-willy@infr= adead.org/ Oh. There is different here: For page cache, large folio could be created by previous file access. But l= ater file access by other process just need map partial large folio. In this cas= e, we need _range for filemap. But for anonymous, I suppose we always map whole folio in. So I agree with = Yu. We don't need _range for folio_add_new_anon_rmap(). Thanks. Regards Yin, Fengwei >=20 >=20 >> >>> void page_add_file_rmap(struct page *, struct vm_area_struct *, >>> bool compound); >>> void folio_add_file_rmap_range(struct folio *, struct page *, unsigned= 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 *folio= , 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 withi= n 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 mapped >>> + * >>> + * Like folio_add_new_anon_rmap() but batch-maps a range of pages with= in a folio >>> + * using non-THP accounting. Like folio_add_new_anon_rmap(), the inc-a= nd-test is >>> + * bypassed and the folio does not have to be locked. All pages in the= folio are >>> + * individually accounted. >>> + * >>> + * As the folio is new, it's assumed to be mapped exclusively by a sin= gle >>> + * process. >>> + */ >>> +void folio_add_new_anon_rmap_range(struct folio *folio, struct page *p= age, >>> + int nr, struct vm_area_struct *vma, unsigned long addre= ss) >>> +{ >>> + 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 >=20 > Thanks, sorry about that. Was copy-pasting from folio_add_new_anon_rmap(). >=20