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[2003:d8:2f01:5500:ba83:3fd7:6836:62f6]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-458705ce685sm26933245e9.30.2025.07.24.10.57.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 24 Jul 2025 10:57:23 -0700 (PDT) Message-ID: <0a70058f-e2fa-4f83-ace5-f58df589ac46@redhat.com> Date: Thu, 24 Jul 2025 19:57:22 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/3] khugepaged: Optimize __collapse_huge_page_copy_succeeded() by PTE batching To: Lorenzo Stoakes , Dev Jain Cc: akpm@linux-foundation.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, baohua@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250724052301.23844-1-dev.jain@arm.com> <20250724052301.23844-3-dev.jain@arm.com> <83c00fa9-37a3-4024-b3d1-20e7749b06c9@lucifer.local> 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/g1oFAmgsLPQFCRvGjuMACgkQTd4Q 9wD/g1o0bxAAqYC7gTyGj5rZwvy1VesF6YoQncH0yI79lvXUYOX+Nngko4v4dTlOQvrd/vhb 02e9FtpA1CxgwdgIPFKIuXvdSyXAp0xXuIuRPQYbgNriQFkaBlHe9mSf8O09J3SCVa/5ezKM OLW/OONSV/Fr2VI1wxAYj3/Rb+U6rpzqIQ3Uh/5Rjmla6pTl7Z9/o1zKlVOX1SxVGSrlXhqt kwdbjdj/csSzoAbUF/duDuhyEl11/xStm/lBMzVuf3ZhV5SSgLAflLBo4l6mR5RolpPv5wad GpYS/hm7HsmEA0PBAPNb5DvZQ7vNaX23FlgylSXyv72UVsObHsu6pT4sfoxvJ5nJxvzGi69U s1uryvlAfS6E+D5ULrV35taTwSpcBAh0/RqRbV0mTc57vvAoXofBDcs3Z30IReFS34QSpjvl Hxbe7itHGuuhEVM1qmq2U72ezOQ7MzADbwCtn+yGeISQqeFn9QMAZVAkXsc9Wp0SW/WQKb76 FkSRalBZcc2vXM0VqhFVzTb6iNqYXqVKyuPKwhBunhTt6XnIfhpRgqveCPNIasSX05VQR6/a OBHZX3seTikp7A1z9iZIsdtJxB88dGkpeMj6qJ5RLzUsPUVPodEcz1B5aTEbYK6428H8MeLq NFPwmknOlDzQNC6RND8Ez7YEhzqvw7263MojcmmPcLelYbfOwU0EVcufkQEQAOfX3n0g0fZz 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+DWgUCaCwtJQUJG8aPFAAKCRBN3hD3AP+DWlDnD/4k2TW+HyOOOePVm23F5HOhNNd7nNv3 Vq2cLcW1DteHUdxMO0X+zqrKDHI5hgnE/E2QH9jyV8mB8l/ndElobciaJcbl1cM43vVzPIWn 01vW62oxUNtEvzLLxGLPTrnMxWdZgxr7ACCWKUnMGE2E8eca0cT2pnIJoQRz242xqe/nYxBB /BAK+dsxHIfcQzl88G83oaO7vb7s/cWMYRKOg+WIgp0MJ8DO2IU5JmUtyJB+V3YzzM4cMic3 bNn8nHjTWw/9+QQ5vg3TXHZ5XMu9mtfw2La3bHJ6AybL0DvEkdGxk6YHqJVEukciLMWDWqQQ RtbBhqcprgUxipNvdn9KwNpGciM+hNtM9kf9gt0fjv79l/FiSw6KbCPX9b636GzgNy0Ev2UV m00EtcpRXXMlEpbP4V947ufWVK2Mz7RFUfU4+ETDd1scMQDHzrXItryHLZWhopPI4Z+ps0rB CQHfSpl+wG4XbJJu1D8/Ww3FsO42TMFrNr2/cmqwuUZ0a0uxrpkNYrsGjkEu7a+9MheyTzcm vyU2knz5/stkTN2LKz5REqOe24oRnypjpAfaoxRYXs+F8wml519InWlwCra49IUSxD1hXPxO WBe5lqcozu9LpNDH/brVSzHCSb7vjNGvvSVESDuoiHK8gNlf0v+epy5WYd7CGAgODPvDShGN g3eXuA== Organization: Red Hat In-Reply-To: <83c00fa9-37a3-4024-b3d1-20e7749b06c9@lucifer.local> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: sInrM4xfhVw7zY_8zcvJyZVpyK2NBw0q6bmBeRVztCk_1753379845 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: 81734160011 X-Stat-Signature: o9up5yhhocy3fdaa9kygtctgfzupr97m X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1753379849-263969 X-HE-Meta: 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 ldlviXf+ 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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: >> + if (folio_test_large(src)) { >> + unsigned int max_nr_ptes = (end - address) >> PAGE_SHIFT; >> + >> + nr_ptes = folio_pte_batch(src, _pte, pteval, max_nr_ptes); >> + } else { >> release_pte_folio(src); >> + } >> + >> /* >> * ptl mostly unnecessary, but preempt has to >> * be disabled to update the per-cpu stats >> * inside folio_remove_rmap_pte(). >> */ >> spin_lock(ptl); >> - ptep_clear(vma->vm_mm, address, _pte); >> - folio_remove_rmap_pte(src, src_page, vma); >> + clear_ptes(vma->vm_mm, address, _pte, nr_ptes); >> + folio_remove_rmap_ptes(src, src_page, nr_ptes, vma); >> spin_unlock(ptl); >> - free_folio_and_swap_cache(src); >> + free_swap_cache(src); >> + folio_put_refs(src, nr_ptes); > > Hm one thing here though is the free_folio_and_swap_cache() does: > > free_swap_cache(folio); > if (!is_huge_zero_folio(folio)) > folio_put(folio); > > Whereas here you unconditionally reduce the reference count. Might this > cause issues with the shrinker version of the huge zero folio? > > Should this be: > > if (!is_huge_zero_folio(src)) > folio_put_refs(src, nr_ptes); > > Or do we otherwise avoid issues with this? (resending my reply) The huge zero folio is never PTE-mapped. -- Cheers, David / dhildenb