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[2003:cb:c742:a100:9dd2:c523:f5fd:da19]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3730810ffb9sm13502148f8f.7.2024.08.27.08.10.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Aug 2024 08:10:08 -0700 (PDT) Message-ID: Date: Tue, 27 Aug 2024 17:10:07 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 5/5] mm: memory_hotplug: unify Huge/LRU/non-LRU movable folio isolation To: Kefeng Wang , Andrew Morton Cc: Oscar Salvador , Miaohe Lin , Naoya Horiguchi , linux-mm@kvack.org References: <20240817084941.2375713-1-wangkefeng.wang@huawei.com> <20240817084941.2375713-6-wangkefeng.wang@huawei.com> <81c2219f-5dcd-4838-8c8d-767b7ff9f714@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-Stat-Signature: 7cqpy9moyb8ink1wjgjfbcp34fmut45t X-Rspamd-Queue-Id: 60DD31C000C X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1724771414-803138 X-HE-Meta: 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 ZgzY79nB MF+D43AOhYiERMRJLdPbwM8rW4Fi9pcSF5PQWh7PMhT42KjgtxSy7GTx3yGZQq28cdzM4EuvO8V6Ls6oIkguxNxRHsRu9M+eGduMb56APZeP3tY7SF6pD2cPaHODfEFWpw5GhGBmaV6d7cOEgXJgkphHXFzxCf6suDe7grfiHUIbRRFWmsCIoHZ8IRE68zK4Bpu9hpBr3aKBMWtM9SY8nS/yzBgnjmACqYShgX39iIx3V/2ChQ620gac8rXX2RfMSUoW7T/C/ZJ0qFR5zcAp1Zn6+Kr+rhJ3/cmaA+BsP6w3sMCwpDVWibnMiyG4MNYzS61rRLvsALnqJn2cWnjnsJK4yBKIPgFSctxdyTKnNRwWidRMWT/kJe0TWLZBkSxLzJLikWWlAQqh1LqaEb1uxQVdVnBnAzgwHrlWbTwUlVACUF+DpIjWd1ygTxEgA7VFMQ9PqMI32x8v3inKXOQDsWgjQBwrDA5bjzJInjzc7QmSji2Q= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000029, 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 27.08.24 03:26, Kefeng Wang wrote: > > > On 2024/8/26 22:55, David Hildenbrand wrote: >> On 17.08.24 10:49, Kefeng Wang wrote: >>> Use the isolate_folio_to_list() to unify hugetlb/LRU/non-LRU >>> folio isolation, which cleanup code a bit and save a few calls >>> to compound_head(). >>> >>> Signed-off-by: Kefeng Wang >>> --- >>>   mm/memory_hotplug.c | 45 +++++++++++++++++---------------------------- >>>   1 file changed, 17 insertions(+), 28 deletions(-) >>> >>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>> index 02a0d4fbc3fe..cc9c16db2f8c 100644 >>> --- a/mm/memory_hotplug.c >>> +++ b/mm/memory_hotplug.c >>> @@ -1773,14 +1773,14 @@ static int scan_movable_pages(unsigned long >>> start, unsigned long end, >>>   static void do_migrate_range(unsigned long start_pfn, unsigned long >>> end_pfn) >>>   { >>>       unsigned long pfn; >>> -    struct page *page; >>>       LIST_HEAD(source); >>> +    struct folio *folio; >>>       static DEFINE_RATELIMIT_STATE(migrate_rs, >>> DEFAULT_RATELIMIT_INTERVAL, >>>                         DEFAULT_RATELIMIT_BURST); >>>       for (pfn = start_pfn; pfn < end_pfn; pfn++) { >>> -        struct folio *folio; >>> -        bool isolated; >>> +        struct page *page; >>> +        bool huge; >> >> Please use "hugetlb" if you mean hugetlb :) > > OK. >> >>>           if (!pfn_valid(pfn)) >>>               continue; >>> @@ -1812,34 +1812,22 @@ static void do_migrate_range(unsigned long >>> start_pfn, unsigned long end_pfn) >>>               continue; >>>           } >>> -        if (folio_test_hugetlb(folio)) { >>> -            isolate_hugetlb(folio, &source); >>> -            continue; >>> +        huge = folio_test_hugetlb(folio); >>> +        if (!huge) { >>> +            folio = folio_get_nontail_page(page); >>> +            if (!folio) >>> +                continue; >>>           } >> >> Hm, remind me why we are changing the hugetlb code to not take a >> reference here? It does look odd. > > Different from folio_isolate_lru(), isolate_hugetlb() will check folio > and try get a reference of folio after get hugetlb_lock, other hugetlb > operation protected by this big lock too, so no need to take a reference > here. But this hugetlb-special casing looks quite ... special TBH. Is there no way to avoid it? I'd prefer something like the following, with a comment if (hugetlb) /* * We also want to migrate hugetlb folios that span multiple * memory blocks. So use whatever head page we identified. */ folio = folio_try_get(folio); else folio = folio_get_nontail_page(page); if (!folio) continue; And then just dropping the reference unconditionally. Is there a problem with that? Optimizing for hugetlb references during migration is not worth the trouble. But now I wonder, why we not simply unconditionally do a folio_try_get() ... -- Cheers, David / dhildenb