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[80.187.83.110]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4255d8e9724sm28761707f8f.28.2025.10.08.02.02.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Oct 2025 02:02:36 -0700 (PDT) Message-ID: Date: Wed, 8 Oct 2025 11:02:34 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/hugetlb: allow overcommitting gigantic hugepages To: Usama Arif , muchun.song@linux.dev, osalvador@suse.de, Andrew Morton Cc: linux-mm@kvack.org, hannes@cmpxchg.org, riel@surriel.com, kas@kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com References: <20251006185607.3257340-1-usamaarif642@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 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: <20251006185607.3257340-1-usamaarif642@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 8oYPw0DuLpyfZbCTWIcIU9e7Hfd2uS4La3aex0nfZNE_1759914157 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: arrkwqppsoxa4jr8e5tkge3uof8y16oq X-Rspamd-Queue-Id: 8585440002 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1759914160-585491 X-HE-Meta: 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 9bPGRGaw ML0P47DToJnB7CEkOTqAOvOAdKL5fihPAXaYs1lvNIDQXklBVtZnLk6DF3gHdFFrFpfJrOY+DmQr6uxB8tQtHt4A8VLQuXrMJe//FQeFgg4ltiQVsV+qkZoWZh0k5hX69lq4R0Y0sWA4POUDMDFAb1g94nxWLrvgK0KdZSNh9iKgPo6LOHYzvvqPfiEVL7dYor+eeHuLM2h8kjG45xWdNSd+n64foEFKlCzHeXRjSuutmaDli44bT4ojUq6xx0Hap9xAQfcKMBXK4c+Dyb7TsJ5nLK8dimabsd0gzFn9z7JyfTMZhRUDzTp27wvehpYG32GSTEO6NO7Tm+3OOQDDGM6EBdyYoBlCcjgtr282FS6j/kkwuH49R7tm1ttMAd8Xl0TWB/IRwMsE1YketR1CgfLUkA5f8bcuEvvYv 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 06.10.25 20:56, Usama Arif wrote: > Currently, gigantic hugepages cannot use the overcommit mechanism > (nr_overcommit_hugepages), forcing users to permanently reserve memory via > nr_hugepages even when pages might not be actively used. > > Remove this blanket restriction on gigantic hugepage overcommit. > This will bring the same benefits to gigantic pages as hugepages: > > - Memory is only taken out of regular use when actually needed > - Unused surplus pages can be returned to the system > - Better memory utilization, especially with CMA backing which can > significantly increase the changes of hugepage allocation > > Without this patch: > echo 3 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_overcommit_hugepages > bash: echo: write error: Invalid argument > > With this patch: > echo 3 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_overcommit_hugepages > ./mmap_hugetlb_test > Successfully allocated huge pages at address: 0x7f9d40000000 > > cat mmap_hugetlb_test.c > ... > unsigned long ALLOC_SIZE = 3 * (unsigned long) HUGE_PAGE_SIZE; > addr = mmap(NULL, > ALLOC_SIZE, // 3GB > PROT_READ | PROT_WRITE, > MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_HUGE_1GB, > -1, > 0); > > if (addr == MAP_FAILED) { > fprintf(stderr, "mmap failed: %s\n", strerror(errno)); > return 1; > } > printf("Successfully allocated huge pages at address: %p\n", addr); > ... > > Signed-off-by: Usama Arif > --- No opinion from my side. I guess it won't harm anybody (but people should be aware that "overcommit" with huge pages where we have no allocation guarantees is a flawed concept). -- Cheers David / dhildenb