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[2003:cb:c731:3d00:918f:ce94:4280:80f0]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-35e0f97ba3csm7719440f8f.73.2024.06.03.02.02.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 03 Jun 2024 02:02:01 -0700 (PDT) Message-ID: Date: Mon, 3 Jun 2024 11:01:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: swap: reuse exclusive folio directly instead of wp page faults To: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org Cc: chrisl@kernel.org, kasong@tencent.com, linux-kernel@vger.kernel.org, minchan@kernel.org, ryan.roberts@arm.com, surenb@google.com, v-songbaohua@oppo.com, willy@infradead.org References: <20240602004502.26895-1-21cnbao@gmail.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: <20240602004502.26895-1-21cnbao@gmail.com> 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: 7bit X-Stat-Signature: d4ktkx5caqrzfkcoms5ri6ykg1r9qk1b X-Rspamd-Queue-Id: E28624001B X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1717405325-333213 X-HE-Meta: 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 2wIk0YQs 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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 02.06.24 02:45, Barry Song wrote: > From: Barry Song > > After swapping out, we perform a swap-in operation. If we first read > and then write, we encounter a major fault in do_swap_page for reading, > along with additional minor faults in do_wp_page for writing. However, > the latter appears to be unnecessary and inefficient. Instead, we can > directly reuse in do_swap_page and completely eliminate the need for > do_wp_page. > > This patch achieves that optimization specifically for exclusive folios. > The following microbenchmark demonstrates the significant reduction in > minor faults. > > #define DATA_SIZE (2UL * 1024 * 1024) > #define PAGE_SIZE (4UL * 1024) > > static void *read_write_data(char *addr) > { > char tmp; > > for (int i = 0; i < DATA_SIZE; i += PAGE_SIZE) { > tmp = *(volatile char *)(addr + i); > *(volatile char *)(addr + i) = tmp; > } > } > > int main(int argc, char **argv) > { > struct rusage ru; > > char *addr = mmap(NULL, DATA_SIZE, PROT_READ | PROT_WRITE, > MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); > memset(addr, 0x11, DATA_SIZE); > > do { > long old_ru_minflt, old_ru_majflt; > long new_ru_minflt, new_ru_majflt; > > madvise(addr, DATA_SIZE, MADV_PAGEOUT); > > getrusage(RUSAGE_SELF, &ru); > old_ru_minflt = ru.ru_minflt; > old_ru_majflt = ru.ru_majflt; > > read_write_data(addr); > getrusage(RUSAGE_SELF, &ru); > new_ru_minflt = ru.ru_minflt; > new_ru_majflt = ru.ru_majflt; > > printf("minor faults:%ld major faults:%ld\n", > new_ru_minflt - old_ru_minflt, > new_ru_majflt - old_ru_majflt); > } while(0); > > return 0; > } > > w/o patch, > / # ~/a.out > minor faults:512 major faults:512 > > w/ patch, > / # ~/a.out > minor faults:0 major faults:512 > > Minor faults decrease to 0! > > Signed-off-by: Barry Song > --- > -v2: > * don't set the dirty flag for read fault, per David; > * make write-protect of uffd_wp clear and remove confusion( > it used to be "wrprotected->writable->wrprotected"), per > David; > Thank you for reviewing, David. > > -v1: > https://lore.kernel.org/linux-mm/20240531104819.140218-1-21cnbao@gmail.com/ > > mm/memory.c | 18 +++++++++++------- > 1 file changed, 11 insertions(+), 7 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index eef4e482c0c2..9696c7397b85 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -4316,6 +4316,10 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > add_mm_counter(vma->vm_mm, MM_ANONPAGES, nr_pages); > add_mm_counter(vma->vm_mm, MM_SWAPENTS, -nr_pages); > pte = mk_pte(page, vma->vm_page_prot); > + if (pte_swp_soft_dirty(vmf->orig_pte)) > + pte = pte_mksoft_dirty(pte); > + if (pte_swp_uffd_wp(vmf->orig_pte)) > + pte = pte_mkuffd_wp(pte); > > /* > * Same logic as in do_wp_page(); however, optimize for pages that are > @@ -4325,18 +4329,18 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > */ > if (!folio_test_ksm(folio) && > (exclusive || folio_ref_count(folio) == 1)) { > - if (vmf->flags & FAULT_FLAG_WRITE) { > - pte = maybe_mkwrite(pte_mkdirty(pte), vma); > - vmf->flags &= ~FAULT_FLAG_WRITE; > + if ((vma->vm_flags & VM_WRITE) && !userfaultfd_pte_wp(vma, pte) && > + !vma_soft_dirty_enabled(vma)) { > + pte = pte_mkwrite(pte, vma); > + if (vmf->flags & FAULT_FLAG_WRITE) { > + pte = pte_mkdirty(pte); > + vmf->flags &= ~FAULT_FLAG_WRITE; > + } > } > rmap_flags |= RMAP_EXCLUSIVE; > } > folio_ref_add(folio, nr_pages - 1); > flush_icache_pages(vma, page, nr_pages); > - if (pte_swp_soft_dirty(vmf->orig_pte)) > - pte = pte_mksoft_dirty(pte); > - if (pte_swp_uffd_wp(vmf->orig_pte)) > - pte = pte_mkuffd_wp(pte); > vmf->orig_pte = pte_advance_pfn(pte, page_idx); > > /* ksm created a completely new copy */ Thanks, LGTM! Acked-by: David Hildenbrand Maybe we really want (likely with better naming) soft_dirty_pte(vma, pte) soft_dirty_pte(vma, pmd) that wrap the VMA+pte check, like we have for uffd-wp. $ git grep vma_soft_dirty | grep -E "(pmd)|(pte)" mm/gup.c: if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd)) mm/gup.c: if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte)) mm/huge_memory.c: if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd)) mm/mprotect.c: if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte)) ... then we could simply use the one here as well. -- Cheers, David / dhildenb