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[2003:cb:c73a:3a00:a025:9b06:549e:c16b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4212b838b55sm144195325e9.5.2024.06.04.01.12.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Jun 2024 01:12:13 -0700 (PDT) Message-ID: <8d3a60d5-06c5-4df4-aeda-2fbec45a8ae0@redhat.com> Date: Tue, 4 Jun 2024 10:12:12 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 02/10] mm/ksm: skip subpages of compound pages To: alexs@kernel.org, Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, izik.eidus@ravellosystems.com, willy@infradead.org, aarcange@redhat.com, chrisw@sous-sol.org, hughd@google.com References: <20240604042454.2012091-1-alexs@kernel.org> <20240604042454.2012091-3-alexs@kernel.org> 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: <20240604042454.2012091-3-alexs@kernel.org> 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-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 4752C40003 X-Stat-Signature: 7ti3z4cebiuhey9fgp9ec5hykqwu9f51 X-HE-Tag: 1717488739-203281 X-HE-Meta: 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 fDnlZgzW JvNuA5xy/57anh2TqWb3DAFtDhvXtxmDlwAOrqNiOYv04H14KzQY3yakUtlQzsymFwtjMQm2W7R/h/Z8dqEg34uxkxNmx8TQ0m5Etf3pZaboheEUseTo0wrQ5bIqOjiBwQQuGo86oxuIUqTgKrE/7W4L3xi1k3yxtzos7OZpFon/dc10Tuut1p5i/VpzfCKgWgyTgJy1vNpIIn/ydAiv+4pXZepMkcwMX+PXjBGE5cgfIs2ZB2YMv4CjLtt2uO/OzMzASvR5xtihCk228h83R1qeAxEtB2Lt9XKCY0yejsKUGtwiFMNeRNE5ktCjub/ESAYPmDG3VhnB3PSOhy0d2MeJL1gyJjGWT+ee/IEBjWLN5T9l8EIn/buTOev2oVSanrj4JOOAammoBcncgtZSdb9dXmF9utmhtkR6g0elFpqE7Tt6g0uIBjvvrOINs2HinOQhCQV/uURjwq0p0o6lY3OrulnVmylBgh3kYOAWuWI+EUXr8bkZ/PVROgCImW2L3LeKk033LphvAWY4= 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 04.06.24 06:24, alexs@kernel.org wrote: > From: "Alex Shi (tencent)" > > When a folio isn't fit for KSM, the subpages are unlikely to be good, > So let's skip the rest page checking to save some actions. > > Signed-off-by: Alex Shi (tencent) > --- > mm/ksm.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/mm/ksm.c b/mm/ksm.c > index 97e5b41f8c4b..e2fdb9dd98e2 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -2644,6 +2644,8 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) > goto no_vmas; > > for_each_vma(vmi, vma) { > + int nr = 1; > + > if (!(vma->vm_flags & VM_MERGEABLE)) > continue; > if (ksm_scan.address < vma->vm_start) > @@ -2660,6 +2662,9 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) > cond_resched(); > continue; > } > + > + VM_WARN_ON(PageTail(*page)); > + nr = compound_nr(*page); > if (is_zone_device_page(*page)) > goto next_page; > if (PageAnon(*page)) { > @@ -2672,7 +2677,7 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) > if (should_skip_rmap_item(*page, rmap_item)) > goto next_page; > > - ksm_scan.address += PAGE_SIZE; > + ksm_scan.address += nr * PAGE_SIZE; > } else > put_page(*page); > mmap_read_unlock(mm); > @@ -2680,7 +2685,7 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) > } > next_page: > put_page(*page); > - ksm_scan.address += PAGE_SIZE; > + ksm_scan.address += nr * PAGE_SIZE; > cond_resched(); > } > } You might be jumping over pages that don't belong to that folio. What you would actually want to do is somehow use folio_pte_batch() to really know the PTEs point at the same folio, so you can skip them. But that's not that easy when using follow_page() ... So I suggest dropping this change for now. -- Cheers, David / dhildenb