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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b788f5f28dsm6505110f8f.10.2025.07.29.06.58.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 29 Jul 2025 06:58:02 -0700 (PDT) Message-ID: <1c821e8c-1d9e-46ca-b0ab-3a897878d883@redhat.com> Date: Tue, 29 Jul 2025 15:58:00 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] /dev/zero: try to align PMD_SIZE for private mapping To: Zhang Qilong , arnd@arndb.de, gregkh@linuxfoundation.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, wangkefeng.wang@huawei.com, sunnanyong@huawei.com, Lorenzo Stoakes References: <20250729134942.900517-1-zhangqilong3@huawei.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/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: <20250729134942.900517-1-zhangqilong3@huawei.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: YJT55l7lgD0osn4aWwiGDWrN1DFbY-QtRVw9wS0l1Ng_1753797487 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-Queue-Id: 83FDF1C000B X-Rspamd-Server: rspam06 X-Stat-Signature: w5r14gxyh1io4ia9znxr36bhwc6u18qa X-HE-Tag: 1753797492-721674 X-HE-Meta: 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 anD4RVmA 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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 29.07.25 15:49, Zhang Qilong wrote: > By default, THP are usually enabled. Mapping /dev/zero with a size > larger than 2MB could achieve performance gains by allocating aligned > address. The mprot_tw4m in libMicro average execution time on arm64: > - Test case: mprot_tw4m > - Before the patch: 22 us > - After the patch: 17 us > > Signed-off-by: Zhang Qilong > --- > drivers/char/mem.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/char/mem.c b/drivers/char/mem.c > index 48839958b0b1..c57327ca9dd6 100644 > --- a/drivers/char/mem.c > +++ b/drivers/char/mem.c > @@ -515,10 +515,12 @@ static int mmap_zero(struct file *file, struct vm_area_struct *vma) > static unsigned long get_unmapped_area_zero(struct file *file, > unsigned long addr, unsigned long len, > unsigned long pgoff, unsigned long flags) > { > #ifdef CONFIG_MMU > + unsigned long ret; Can we call that "addr" like we do in __get_unmapped_area()? Nothing else jumped at me ... so I assume this is fine? CCing mmap-man Lorenzo. -- Cheers, David / dhildenb