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[149.14.88.26]) by smtp.gmail.com with ESMTPSA id i22-20020a05600c355600b0041277b5da5csm797595wmq.36.2024.02.21.01.15.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 21 Feb 2024 01:15:33 -0800 (PST) Message-ID: <4c1224e3-5c02-4d5d-9379-d3b74b1174dd@redhat.com> Date: Wed, 21 Feb 2024 10:15:32 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] madvise:madvise_cold_or_pageout_pte_range(): allow split while folio_estimated_sharers = 0 To: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Barry Song , Yin Fengwei , Yu Zhao , Ryan Roberts , Kefeng Wang , Matthew Wilcox , Minchan Kim , Vishal Moola , Yang Shi References: <20240221085036.105621-1-21cnbao@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: <20240221085036.105621-1-21cnbao@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-Rspamd-Queue-Id: C79FE18001D X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: aes7h43jjx9t7jrpyr5tohm7mcgyje64 X-HE-Tag: 1708506937-852416 X-HE-Meta: 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 T8snqkXq 96sCXOL2fbGjpO35zY0RGQZPGu0a4b5nXR7jBLdlgkgGDvC7sS67FWTmAXi9MsZ1keBUk16yHOVY1GejjuB/YHS1EDswv1VnEG8zwy2UC10zRgIXbQADsTKlT+EXAK3M9DQXBHFqpQwt+y7blOGFq9RCSutnBNtJOyvJbBaMb9rReqPgXJms0NInXq7tuLheWRvkkkU9vT2xF8Lq1xdMRhmJ1+YYRV/HcO+DXMXrx5WqXtyPAuYX+70u7FuEb2HrMkeEFcMdZHDV58MbN5EQuCVZSpt79Pj3ih9wV 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 21.02.24 09:50, Barry Song wrote: > From: Barry Song > > The purpose is stopping splitting large folios whose mapcount are 2 or > above. Folios whose estimated_shares = 0 should be still perfect and > even better candidates than estimated_shares = 1. > > Consider a pte-mapped large folio with 16 subpages, if we unmap 1-15, > the current code will split folios and reclaim them while madvise goes > on this folio; but if we unmap subpage 0, we will keep this folio and > break. This is weird. > > For pmd-mapped large folios, we can still use "= 1" as the condition > as anyway we have the entire map for it. So this patch doesn't change > the condition for pmd-mapped large folios. > This also explains why we had been using "= 1" for both pmd-mapped and > pte-mapped large folios before commit 07e8c82b5eff ("madvise: convert > madvise_cold_or_pageout_pte_range() to use folios"), because in the > past, we used the mapcount of the specific subpage, since the subpage > had pte present, its mapcount wouldn't be 0. > > The problem can be quite easily reproduced by writing a small program, > unmapping the first subpage of a pte-mapped large folio vs. unmapping > anyone other than the first subpage. > > Fixes: 2f406263e3e9 ("madvise:madvise_cold_or_pageout_pte_range(): don't use mapcount() against large folio for sharing check") > Cc: Yin Fengwei > Cc: Yu Zhao > Cc: Ryan Roberts > Cc: David Hildenbrand > Cc: Kefeng Wang > Cc: Matthew Wilcox > Cc: Minchan Kim > Cc: Vishal Moola (Oracle) > Cc: Yang Shi > Signed-off-by: Barry Song > --- > mm/madvise.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index cfa5e7288261..abde3edb04f0 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -453,7 +453,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, > if (folio_test_large(folio)) { > int err; > > - if (folio_estimated_sharers(folio) != 1) > + if (folio_estimated_sharers(folio) > 1) > break; > if (pageout_anon_only_filter && !folio_test_anon(folio)) > break; That's also what I do in https://lkml.kernel.org/r/20231124132626.235350-4-david@redhat.com I'll revive that soon. -- Cheers, David / dhildenb