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[2003:cb:c724:7a00:871b:454b:d552:c4ed]) by smtp.gmail.com with ESMTPSA id n17-20020adfe791000000b00349be95b5cesm7191251wrm.101.2024.04.20.09.31.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 20 Apr 2024 09:31:59 -0700 (PDT) Message-ID: Date: Sat, 20 Apr 2024 18:31:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] mm/vmscan: avoid split PMD-mapped THP during shrink_folio_list() To: Lance Yang , Matthew Wilcox Cc: akpm@linux-foundation.org, maskray@google.com, ziy@nvidia.com, ryan.roberts@arm.com, 21cnbao@gmail.com, mhocko@suse.com, fengwei.yin@intel.com, zokeefe@google.com, shy828301@gmail.com, xiehuan09@gmail.com, wangkefeng.wang@huawei.com, songmuchun@bytedance.com, peterx@redhat.com, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240417141111.77855-1-ioworker0@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: 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: rspam09 X-Rspamd-Queue-Id: F16DC4001E X-Stat-Signature: 9bs1dz5568brt4c1pyqi1yph1zuk4qkh X-Rspam-User: X-HE-Tag: 1713630723-379258 X-HE-Meta: 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 t7oWOwQV 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 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 20.04.24 17:04, Lance Yang wrote: > On Sat, Apr 20, 2024 at 12:59 PM Lance Yang wrote: >> >> Hey Matthew, >> >> Thanks for taking time to review! >> >> On Wed, Apr 17, 2024 at 11:09 PM Matthew Wilcox wrote: >>> >>> On Wed, Apr 17, 2024 at 10:11:11PM +0800, Lance Yang wrote: >>>> When the user no longer requires the pages, they would use madvise(madv_free) >>>> to mark the pages as lazy free. IMO, they would not typically rewrite to the >>>> given range. >>>> >>>> At present, a PMD-mapped THP marked as lazyfree during shrink_folio_list() >>>> is unconditionally split, which may be unnecessary. If the THP is exclusively >>>> mapped and clean, and the PMD associated with it is also clean, then we can >>>> attempt to remove the PMD mapping from it. This change will improve the >>>> efficiency of memory reclamation in this case. >>>> >>>> On an Intel i5 CPU, reclaiming 1GiB of PMD-mapped THPs using >>>> mem_cgroup_force_empty() results in the following runtimes in seconds >>>> (shorter is better): >>>> >>>> -------------------------------------------- >>>> | Old | New | Change | >>>> -------------------------------------------- >>>> | 0.683426 | 0.049197 | -92.80% | >>>> -------------------------------------------- >>>> >>>> Signed-off-by: Lance Yang >>>> --- >>>> include/linux/huge_mm.h | 1 + >>>> include/linux/rmap.h | 1 + >>>> mm/huge_memory.c | 2 +- >>>> mm/rmap.c | 81 +++++++++++++++++++++++++++++++++++++++++ >>>> mm/vmscan.c | 7 ++++ >>>> 5 files changed, 91 insertions(+), 1 deletion(-) >>> >>> I'm confused why we need all this extra code. If we remove a folio >> >> Thanks for pointing that out! >> >> I've added a lot of extra code to rmap.c, and we don't need it >> for file pages - sorry. I'll reconsider where to place this code. >> >>> from the pagecache, we can just call truncate_inode_folio() and >>> unmap_mapping_folio() takes care of all the necessary unmappings. >>> Why can't you call unmap_mapping_folio() here? >> >> Thanks for your suggestion. >> >> But this change only avoids the splitting of *anon* large folios >> (PMD-mapped THPs) that are marked as lazyfree during >> shrink_folio_list(). >> >> IIUC, in some cases, we cannot unmap the THP marked as lazyfree >> here, such as when it's not exclusively mapped, dirty, pinned, etc. > > I’d like to make a correction. > > IMO, we can unmap the THP that is not exclusively mapped, but > ensuring folio_ref_count() equals folio_mapcount() +1. You must follow the exact same logic as in try_to_unmap_one() I guess. That is, unmap the page, syncing against concurrent GUP-fast. Then, check mapcount vs. refcount. If there are unexpected references, remap the page (set_pte_at). -- Cheers, David / dhildenb