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Thu, 11 Jul 2024 12:53:50 -0700 (PDT) Received: from [10.35.209.243] ([208.115.86.72]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-70b438c6f83sm6074995b3a.82.2024.07.11.12.53.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Jul 2024 12:53:49 -0700 (PDT) Message-ID: Date: Thu, 11 Jul 2024 21:53:48 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v22 1/4] mm: add MAP_DROPPABLE for designating always lazily freeable mappings To: Yu Zhao Cc: "Jason A. Donenfeld" , Linus Torvalds , linux-kernel@vger.kernel.org, patches@lists.linux.dev, tglx@linutronix.de, linux-crypto@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, Greg Kroah-Hartman , Adhemerval Zanella Netto , Carlos O'Donell , Florian Weimer , Arnd Bergmann , Jann Horn , Christian Brauner , David Hildenbrand , linux-mm@kvack.org References: <98798483-dfcd-451e-94bb-57d830bf68d8@redhat.com> <54b6de32-f127-4928-9f4a-acb8653e5c81@redhat.com> <8586b19c-2e14-4164-888f-8c3b86f3f963@redhat.com> <443146f4-9db8-4a19-91f1-b6822fad8ce8@redhat.com> <1c8632b4-06a5-49da-be0c-6fc7ac2b3257@redhat.com> <2c464271-1c61-4cd8-bd4e-4bd8aa01fa00@redhat.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-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: C55B9C001D X-Stat-Signature: j76ab8i9geamfdt1sbnz74n8cjgyeeny X-Rspam-User: X-HE-Tag: 1720727633-954636 X-HE-Meta: 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 U1pmfkRR Qs3K7xYO0NhDD7KLKRE3wQk5zWRe46q+l0mkQkGtxgGVoMN498D0HoKE1h0fnkI+kUd9EAAW38YWGrygH3LHmEGI6pjsRhIqLU8wkjHWkcZ2bBhBwDxjP7Z7MAcLdxAEWD7Y/Nt7sW8UQumfItjH9uZgJn9mD8uu4jzi03vY1bQI2tQOknopvj6U9Pf+n6LuqRaP3/+X73bY9VtSXknJBcIBSqFU1TmNQniehCvs/JSWwx/00OkU850ZR4ViPBN8VeA/5b63hSCnWojJN9Gl9XsNLuxi6IuZq9BkXIG4UFG916O5TvJcDdMhumnvO74ObH3udhENsc2J+L/QfmLi0MhWgveu7uLo7cKTDjqKyTu7E3/k0GtBwYwHX9RlN3cj99tfXplsZuwMGBIyV50yij4gBCFCrA3ohJYrCJXEzEjCM2/5xF8Rk76LFuDLBY3Ho0XIO4AkCxc7WnGiU5mJKdEQueUlWKiCdfhPz 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 11.07.24 21:49, Yu Zhao wrote: > On Thu, Jul 11, 2024 at 1:20 PM David Hildenbrand wrote: >> >> On 11.07.24 21:18, David Hildenbrand wrote: >>> On 11.07.24 20:56, David Hildenbrand wrote: >>>> On 11.07.24 20:54, Jason A. Donenfeld wrote: >>>>> On Thu, Jul 11, 2024 at 08:24:07PM +0200, David Hildenbrand wrote: >>>>>>> And PG_large_rmappable seems to only be used for hugetlb branches. >>>>>> >>>>>> It should be set for THP/large folios. >>>>> >>>>> And it's tested too, apparently. >>>>> >>>>> Okay, well, how disappointing is this below? Because I'm running out of >>>>> tricks for flag reuse. >>>>> >>>>> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h >>>>> index b9e914e1face..c1ea49a7f198 100644 >>>>> --- a/include/linux/page-flags.h >>>>> +++ b/include/linux/page-flags.h >>>>> @@ -110,6 +110,7 @@ enum pageflags { >>>>> PG_workingset, >>>>> PG_error, >>>>> PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/ >>>>> + PG_owner_priv_2, >>>> >>>> Oh no, no new page flags please :) >>>> >>>> Maybe just follow what Linux suggested: pass vma to pte_dirty() and >>>> always return false for these special VMAs. >>> >>> ... or look into removing that one case that gives us headake. >>> >>> No idea what would happen if we do the following: >>> >>> CCing Yu Zhao. >>> >>> diff --git a/mm/vmscan.c b/mm/vmscan.c >>> index 0761f91b407f..d1dfbd4fd38d 100644 >>> --- a/mm/vmscan.c >>> +++ b/mm/vmscan.c >>> @@ -4280,14 +4280,9 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c >>> return true; >>> } >>> >>> - /* dirty lazyfree */ >>> - if (type == LRU_GEN_FILE && folio_test_anon(folio) && folio_test_dirty(folio)) { >>> - success = lru_gen_del_folio(lruvec, folio, true); >>> - VM_WARN_ON_ONCE_FOLIO(!success, folio); >>> - folio_set_swapbacked(folio); >>> - lruvec_add_folio_tail(lruvec, folio); >>> - return true; >>> - } >>> + /* lazyfree: we may not be allowed to set swapbacked: MAP_DROPPABLE */ >>> + if (type == LRU_GEN_FILE && folio_test_anon(folio) && folio_test_dirty(folio)) >>> + return false; > > This is an optimization to avoid an unnecessary trip to > shrink_folio_list(), so it's safe to delete the entire 'if' block, and > that would be preferable than leaving a dangling 'if'. Great, thanks. > >> Note that something is unclear to me: are we maybe running into that >> code also if folio_set_swapbacked() is already set and we are not in the >> lazyfree path (in contrast to what is documented)? > > Not sure what you mean: either rmap sees pte_dirty() and does > folio_mark_dirty() and then folio_set_swapbacked(); or MGLRU does the > same sequence, with the first two steps in walk_pte_range() and the > last one here. Let me rephrase: Checking for lazyfree is "folio_test_anon(folio) && !folio_test_swapbacked(folio)" Testing for dirtied lazyfree is "folio_test_anon(folio) && !folio_test_swapbacked(folio) && folio_test)dirty(folio)" So I'm wondering about the missing folio_test_swapbacked() test. -- Cheers, David / dhildenb