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[79.224.251.251]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3cf275d2722sm22600275f8f.19.2025.09.02.23.52.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 Sep 2025 23:52:36 -0700 (PDT) Message-ID: Date: Wed, 3 Sep 2025 08:52:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm: Enable khugepaged to operate on non-writable VMAs To: Dev Jain , akpm@linux-foundation.org, kas@kernel.org, willy@infradead.org, hughd@google.com Cc: ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.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: <20250903054635.19949-1-dev.jain@arm.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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20250903054635.19949-1-dev.jain@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: XEoXLL5GHBAslMVgqdG0MCHDv66ofIvVrGcYlAFhwZA_1756882357 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: EED6920006 X-Rspam-User: X-Stat-Signature: cfxohw5us3wj11kppskj5u9eaxdh8q8r X-Rspamd-Server: rspam09 X-HE-Tag: 1756882362-140528 X-HE-Meta: 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 gt9eNHFf 7wO5ggJTsE8nBQFSdIqgb/UC5OwaOJoSrMGKiDMlpxKqO3Xts8Vrpi6LTK7hFOQcLYX3lAF6MJLxDO9wm4KvF8+O/O1Acc6X007Kg7Cj0nExdJOLeVpR4DFWU0OYL7KMBOZgeEBwiLjbD9sGOdQM5Jn1dq2HO7oQCi5nPOP+a/FXDtYaTg/y67p6q5lR3G5Bdmw3Lp7jHwaaYsV86IrU438n4exloiASOssaXnaPLQ15apYiGFmCSZAQuvHU0dUiMGS5cHYK27r/sDdfsNuLhdTt/zhTpMIv7j9RypmjSw7ihew7gB+K8L9ns/hTEyMkuH6E489ZzMvz3uiDAIs2qjIdP4+Djgf5qVlDFtNg048pvndlOp1i4oiRbcF0d4pk32vU81T4gE1HjiOQ9uaMfDpjro8bdDOr+8eWxJnfaAXzWzYka1gZObVNJ3CQHewJdh3TrEGJaUv72vf0z5B571jgFjQ== 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 03.09.25 07:46, Dev Jain wrote: > Currently khugepaged does not collapse a region which does not have a > single writable page. This is wasteful since non-writable VMAs mapped by > the application won't benefit from THP collapse. Therefore, remove this > restriction and allow khugepaged to collapse a VMA with arbitrary > protections. > > Along with this, currently MADV_COLLAPSE does not perform a collapse on a > non-writable VMA, and this restriction is nowhere to be found on the > manpage - the restriction itself sounds wrong to me since the user knows > the protection of the memory it has mapped, so collapsing read-only > memory via madvise() should be a choice of the user which shouldn't > be overriden by the kernel. > > On an arm64 machine, an average of 5% improvement is seen on some mmtests > benchmarks, particularly hackbench, with a maximum improvement of 12%. > > Signed-off-by: Dev Jain > --- Acked-by: David Hildenbrand -- Cheers David / dhildenb