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[2003:cb:c707:7600:5c18:5a7d:c5b7:e7a9]) by smtp.gmail.com with ESMTPSA id bj29-20020a0560001e1d00b0033d81d9c44esm10925634wrb.70.2024.02.27.01.36.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Feb 2024 01:36:43 -0800 (PST) Message-ID: <42ffe7cf-8371-433d-a9bf-1a23c902f3f9@redhat.com> Date: Tue, 27 Feb 2024 10:36:42 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: export folio_pte_batch as a couple of modules might need it To: Barry Song <21cnbao@gmail.com> Cc: Ryan Roberts , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Barry Song , Lance Yang , Yin Fengwei References: <20240227024050.244567-1-21cnbao@gmail.com> <61b9dfc9-5522-44fd-89a4-140833ede8af@arm.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 4D70D160007 X-Stat-Signature: af4t1gj3oaarqaorscpedbmkkcarj547 X-HE-Tag: 1709026608-491575 X-HE-Meta: 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 tlw65VgM 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 27.02.24 10:27, Barry Song wrote: > On Tue, Feb 27, 2024 at 10:14 PM David Hildenbrand wrote: >> >> On 27.02.24 10:07, Ryan Roberts wrote: >>> On 27/02/2024 02:40, Barry Song wrote: >>>> From: Barry Song >>>> >>>> madvise and some others might need folio_pte_batch to check if a range >>>> of PTEs are completely mapped to a large folio with contiguous physcial >>>> addresses. Let's export it for others to use. >>>> >>>> Cc: Lance Yang >>>> Cc: Ryan Roberts >>>> Cc: David Hildenbrand >>>> Cc: Yin Fengwei >>>> Signed-off-by: Barry Song >>>> --- >>>> -v1: >>>> at least two jobs madv_free and madv_pageout depend on it. To avoid >>>> conflicts and dependencies, after discussing with Lance, we prefer >>>> this one can land earlier. >>> >>> I think this will also ultimately be useful for mprotect too, though I haven't >>> looked at it properly yet. >>> >> >> Yes, I think we briefly discussed that. >> >>>> >>>> mm/internal.h | 13 +++++++++++++ >>>> mm/memory.c | 11 +---------- >>>> 2 files changed, 14 insertions(+), 10 deletions(-) >>>> >>>> diff --git a/mm/internal.h b/mm/internal.h >>>> index 13b59d384845..8e2bc304f671 100644 >>>> --- a/mm/internal.h >>>> +++ b/mm/internal.h >>>> @@ -83,6 +83,19 @@ static inline void *folio_raw_mapping(struct folio *folio) >>>> return (void *)(mapping & ~PAGE_MAPPING_FLAGS); >>>> } >>>> >>>> +/* Flags for folio_pte_batch(). */ >>>> +typedef int __bitwise fpb_t; >>>> + >>>> +/* Compare PTEs after pte_mkclean(), ignoring the dirty bit. */ >>>> +#define FPB_IGNORE_DIRTY ((__force fpb_t)BIT(0)) >>>> + >>>> +/* Compare PTEs after pte_clear_soft_dirty(), ignoring the soft-dirty bit. */ >>>> +#define FPB_IGNORE_SOFT_DIRTY ((__force fpb_t)BIT(1)) >>>> + >>>> +extern int folio_pte_batch(struct folio *folio, unsigned long addr, >>>> + pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags, >>>> + bool *any_writable); >>>> + >>>> void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio, >>>> int nr_throttled); >>>> static inline void acct_reclaim_writeback(struct folio *folio) >>>> diff --git a/mm/memory.c b/mm/memory.c >>>> index 1c45b6a42a1b..319b3be05e75 100644 >>>> --- a/mm/memory.c >>>> +++ b/mm/memory.c >>>> @@ -953,15 +953,6 @@ static __always_inline void __copy_present_ptes(struct vm_area_struct *dst_vma, >>>> set_ptes(dst_vma->vm_mm, addr, dst_pte, pte, nr); >>>> } >>>> >>>> -/* Flags for folio_pte_batch(). */ >>>> -typedef int __bitwise fpb_t; >>>> - >>>> -/* Compare PTEs after pte_mkclean(), ignoring the dirty bit. */ >>>> -#define FPB_IGNORE_DIRTY ((__force fpb_t)BIT(0)) >>>> - >>>> -/* Compare PTEs after pte_clear_soft_dirty(), ignoring the soft-dirty bit. */ >>>> -#define FPB_IGNORE_SOFT_DIRTY ((__force fpb_t)BIT(1)) >>>> - >>>> static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags) >>>> { >>>> if (flags & FPB_IGNORE_DIRTY) >>>> @@ -982,7 +973,7 @@ static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags) >>>> * If "any_writable" is set, it will indicate if any other PTE besides the >>>> * first (given) PTE is writable. >>>> */ >>> >>> David was talking in Lance's patch thread, about improving the docs for this >>> function now that its exported. Might be worth syncing on that. >> >> Here is my take: >> >> Signed-off-by: David Hildenbrand >> --- >> mm/memory.c | 22 ++++++++++++++++++---- >> 1 file changed, 18 insertions(+), 4 deletions(-) >> >> diff --git a/mm/memory.c b/mm/memory.c >> index d0b855a1837a8..098356b8805ae 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -971,16 +971,28 @@ static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags) >> return pte_wrprotect(pte_mkold(pte)); >> } >> >> -/* >> +/** >> + * folio_pte_batch - detect a PTE batch for a large folio >> + * @folio: The large folio to detect a PTE batch for. >> + * @addr: The user virtual address the first page is mapped at. >> + * @start_ptep: Page table pointer for the first entry. >> + * @pte: Page table entry for the first page. >> + * @max_nr: The maximum number of table entries to consider. >> + * @flags: Flags to modify the PTE batch semantics. >> + * @any_writable: Optional pointer to indicate whether any entry except the >> + * first one is writable. >> + * >> * Detect a PTE batch: consecutive (present) PTEs that map consecutive >> - * pages of the same folio. >> + * pages of the same large folio. >> * >> * All PTEs inside a PTE batch have the same PTE bits set, excluding the PFN, >> * the accessed bit, writable bit, dirty bit (with FPB_IGNORE_DIRTY) and >> * soft-dirty bit (with FPB_IGNORE_SOFT_DIRTY). >> * >> - * If "any_writable" is set, it will indicate if any other PTE besides the >> - * first (given) PTE is writable. >> + * start_ptep must map any page of the folio. max_nr must be at least one and >> + * must be limited by the caller so scanning cannot exceed a single page table. >> + * >> + * Return: the number of table entries in the batch. >> */ >> static inline int folio_pte_batch(struct folio *folio, unsigned long addr, >> pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags, >> @@ -996,6 +1008,8 @@ static inline int folio_pte_batch(struct folio *folio, unsigned long addr, >> *any_writable = false; >> >> VM_WARN_ON_FOLIO(!pte_present(pte), folio); >> + VM_WARN_ON_FOLIO(!folio_test_large(folio) || max_nr < 1, folio); >> + VM_WARN_ON_FOLIO(page_folio(pfn_to_page(pte_pfn(pte))) != folio, folio); >> >> nr = pte_batch_hint(start_ptep, pte); >> expected_pte = __pte_batch_clear_ignored(pte_advance_pfn(pte, nr), flags); >> -- >> 2.43.2 >> >> >>> >>>> -static inline int folio_pte_batch(struct folio *folio, unsigned long addr, >>>> +int folio_pte_batch(struct folio *folio, unsigned long addr, >>> >>> fork() is very performance sensitive. Is there a risk we are regressing >>> performance by making this out-of-line? Although its in the same compilation >>> unit so the compiler may well inline it anyway? >> >> Easy to verify by looking at the generated asm I guess? > > my aarch64-linux-gnu-gcc didn't inline it I think on x86-64 it would inline it with "gcc (GCC) 13.2.1 20231205 (Red Hat 13.2.1-6)" > > $ aarch64-linux-gnu-gcc --version > aarch64-linux-gnu-gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0 > Copyright (C) 2021 Free Software Foundation, Inc. > > $ nm -S -s vmlinux.a | grep folio_pte_batch > 0000000000003818 0000000000000204 T folio_pte_batch > As it's only used on the folio_test_large() "slower" paths, likely optimizing out the "writable" check (and possibly the flags) might not be that important. >> >>> >>> Either way, perhaps we are better off making it inline in the header? That would >>> avoid needing to rerun David's micro-benchmarks for fork() and munmap(). > > actually tried this before trying extern, the problem is that we have to add > others into internal.h, for example __pte_batch_clear_ignored, which > seems not API. are we comfortable to move that one to internal.h too? Yes, that shouldn't stop us. -- Cheers, David / dhildenb