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[2003:d8:2f27:ec00:4f4d:d38:ba97:9aa2]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a5253a7a2fsm2368776f8f.18.2025.06.05.00.51.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Jun 2025 00:51:07 -0700 (PDT) Message-ID: <9b04871b-33fb-42cb-840b-88fdb6b93c48@redhat.com> Date: Thu, 5 Jun 2025 09:51:06 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] gup: optimize longterm pin_user_pages() for large folio To: lizhe.67@bytedance.com, akpm@linux-foundation.org, jgg@ziepe.ca, jhubbard@nvidia.com, peterx@redhat.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, dev.jain@arm.com, muchun.song@linux.dev References: <20250605033430.83142-1-lizhe.67@bytedance.com> From: David Hildenbrand Content-Language: en-US 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: <20250605033430.83142-1-lizhe.67@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 05.06.25 05:34, lizhe.67@bytedance.com wrote: > From: Li Zhe > > In the current implementation of the longterm pin_user_pages() function, > we invoke the collect_longterm_unpinnable_folios() function. This function > iterates through the list to check whether each folio belongs to the > "longterm_unpinnabled" category. The folios in this list essentially > correspond to a contiguous region of user-space addresses, with each folio > representing a physical address in increments of PAGESIZE. If this > user-space address range is mapped with large folio, we can optimize the > performance of function collect_longterm_unpinnable_folios() by reducing > the using of READ_ONCE() invoked in > pofs_get_folio()->page_folio()->_compound_head(). Also, we can simplify > the logic of collect_longterm_unpinnable_folios(). Instead of comparing > with prev_folio after calling pofs_get_folio(), we can check whether the > next page is within the same folio. > > The performance test results, based on v6.15, obtained through the > gup_test tool from the kernel source tree are as follows. We achieve an > improvement of over 66% for large folio with pagesize=2M. For small folio, > we have only observed a very slight degradation in performance. > > Without this patch: > > [root@localhost ~] ./gup_test -HL -m 8192 -n 512 > TAP version 13 > 1..1 > # PIN_LONGTERM_BENCHMARK: Time: get:14391 put:10858 us# > ok 1 ioctl status 0 > # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 > [root@localhost ~]# ./gup_test -LT -m 8192 -n 512 > TAP version 13 > 1..1 > # PIN_LONGTERM_BENCHMARK: Time: get:130538 put:31676 us# > ok 1 ioctl status 0 > # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 > > With this patch: > > [root@localhost ~] ./gup_test -HL -m 8192 -n 512 > TAP version 13 > 1..1 > # PIN_LONGTERM_BENCHMARK: Time: get:4867 put:10516 us# > ok 1 ioctl status 0 > # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 > [root@localhost ~]# ./gup_test -LT -m 8192 -n 512 > TAP version 13 > 1..1 > # PIN_LONGTERM_BENCHMARK: Time: get:131798 put:31328 us# > ok 1 ioctl status 0 > # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 > > Signed-off-by: Li Zhe > --- > Changelogs: > > v2->v3: > - Update performance test data based on v6.15. > - Refine the description of the optimization approach in commit message. > - Fix some issues of code formatting. > - Fine-tune the conditions for entering the optimization path. > > v1->v2: > - Modify some unreliable code. > - Update performance test data. > > v2 patch: https://lore.kernel.org/all/20250604031536.9053-1-lizhe.67@bytedance.com/ > v1 patch: https://lore.kernel.org/all/20250530092351.32709-1-lizhe.67@bytedance.com/ > > mm/gup.c | 37 +++++++++++++++++++++++++++++-------- > 1 file changed, 29 insertions(+), 8 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index 84461d384ae2..9fbe3592b5fc 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -2317,6 +2317,31 @@ static void pofs_unpin(struct pages_or_folios *pofs) > unpin_user_pages(pofs->pages, pofs->nr_entries); > } > > +static struct folio *pofs_next_folio(struct folio *folio, > + struct pages_or_folios *pofs, long *index_ptr) ^ use two tabs here > +{ > + long i = *index_ptr + 1; > + > + if (!pofs->has_folios && folio_test_large(folio)) { > + const unsigned long start_pfn = folio_pfn(folio); > + const unsigned long end_pfn = start_pfn + folio_nr_pages(folio); > + > + for (; i < pofs->nr_entries; i++) { > + unsigned long pfn = page_to_pfn(pofs->pages[i]); > + > + /* Is this page part of this folio? */ > + if (pfn < start_pfn || pfn >= end_pfn) > + break; > + } > + } > + > + if (unlikely(i == pofs->nr_entries)) > + return NULL; > + *index_ptr = i; > + > + return pofs_get_folio(pofs, i); > +} > + > /* > * Returns the number of collected folios. Return value is always >= 0. > */ > @@ -2324,16 +2349,12 @@ static void collect_longterm_unpinnable_folios( > struct list_head *movable_folio_list, > struct pages_or_folios *pofs) > { > - struct folio *prev_folio = NULL; > bool drain_allow = true; > - unsigned long i; > - > - for (i = 0; i < pofs->nr_entries; i++) { > - struct folio *folio = pofs_get_folio(pofs, i); > + struct folio *folio; > + long i = 0; > > - if (folio == prev_folio) > - continue; > - prev_folio = folio; > + for (folio = pofs_get_folio(pofs, i); folio; > + folio = pofs_next_folio(folio, pofs, &i)) { As discussed, align both "folios" (using tabs and then spaces) Acked-by: David Hildenbrand -- Cheers, David / dhildenb