From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 67B584457A6; Fri, 11 Sep 2026 11:09:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789124942; cv=none; b=M72w70EUNZw8r95TzgQktt7PC+x5fBemV0rGuJc+TRUQN5wPbLPx2mYgXPVfLGtaVVrE+II3dnpGQf4IML2FQSgV9ibHbfpy1N1zPxOKJEpKc2tIVlTsdjPpLqkjaDYQ8zpQvczYm20guFlMkyB223f01XsckeS/1pRis11Ej4w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789124942; c=relaxed/simple; bh=9EuvcvyokWIr5lp8zE4aZ/qzfPErdBcMkQga6O6vQJE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=SdJITV4qyMU0rsve48zuZt45XSuFq17F5gWHO7CKPM0djdReyqrJTAN/wLkSCyvt5u2DvKnfHcRX+FOE54jC5swqxWqdWbINcuQ5lqn+7nr7FCl9F4m5P2lsrlW/Ul5OWnSMClMe4NWkbajT+AB5wiSpfDRxyKBaE0ymCowjqBY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gC3880N7; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="gC3880N7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ABF1A1F000FF; Fri, 11 Sep 2026 11:08:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789124940; bh=6ygcdnQ69In0ilSwlGhITt/klmABXMlT7Ds7dNoRszA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=gC3880N7e8W3doV9TCZFw9rw0iMCANVgDewTgiorw4xFJbxopkGieOb+PwS6w6yEK EFU7ECwpxoK0Jtx9uaK54xOQfl4Phf+XW94wQs0nC5Zw6HY4ZOVT8asix/QraMPSKN WVDnjjQx+csPiMXjB/7icM71AG/X4QHkgijLXNbSDPz9L7/fwcycRtbdnzJA5Ivnxb B8ShR1utBRL5LNy0mak9ADaHCaDPJF91fFlwh0ttZ1zHngwvT7zIg8u8RUx06A3yKL dZO/rPPRh/uep9AtUDw6QGnMFRshPc1wvDHKu3DblMSvoNb5F1Wwl2mFp4FGv6EiPY 2OWGFZaucJcLg== Message-ID: Date: Fri, 11 Sep 2026 13:08:51 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 6/6] selftests/mm: add a GUP selftest To: Sarthak Sharma , Andrew Morton Cc: Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Shuah Khan , Jonathan Corbet , Jason Gunthorpe , John Hubbard , Peter Xu , Leon Romanovsky , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Mark Brown , Anshuman Khandual , Muhammad Usama Anjum , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260904123631.198697-1-sarthak.sharma@arm.com> <20260904123631.198697-7-sarthak.sharma@arm.com> <5e0b9365-cbac-4f2d-b915-85edf3093508@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/11/26 06:32, Sarthak Sharma wrote: > Hi David! > > On 9/9/26 10:33 PM, David Hildenbrand (Arm) wrote: >>> >>> This is an interesting change. We can keep this open for discussion >>> here. If required, I can work on this in the future. >> >> Yes, we should in general try moving all test modules out of the core. >> >>> >>> This is a pre requisite check. Every test opens and closes /dev/zero and >>> /sys/kernel/debug/gup_test of its own. So I wanted to check before >>> running the harness if these two are available, so that we don't have >>> setup failures for 60 test cases. >> >> But why /dev/zero? We should understand why that would possibly be required. > > This was carried over from the old test, where /dev/zero was the default > backing for mmap unless the user selected another file to back the > mapping. Now since we don't support file backed mappings, we can > directly use MAP_ANONYMOUS here. Thanks for pointing it out, I'll remove > it from this patch. > >> >>> >>> >>> mm selftests normally skip if the test is not run as root. So I tried >>> keeping the same thing here. Do you think I should change it to fail? >> >> If other tests do that, it's fine! >> >> [...] >> >>> >>> HUGETLB_TARGET_SIZE is the target mapping size and >>> default_huge_page_size() gives the size of a single hugetlb page. >>> >>> Using default_huge_page_size() would reduce coverage for 2MB hugetlb >>> pages. The old test set self->size to be 256 MB for the hugetlb case. >>> >>> Now it was discussed in a previous version of this patchset that we can >>> derive the self->size for hugetlb case by fixing the nr_hugepages and >>> multiplying by hugetlb size, and thought 128 would be a good number for >>> nr_hugepages [1]. >>> >>> But in case the hugetlb pages are very large, eg we can have 1 GB >>> hugepages as well, reserving 128 GB is not a good idea. So I tried to >>> keep the target size of the mapping as 256 MB, as it was before in the >>> old gup test. If the hugetlb pages are larger than this, we'll reserve >>> only one of them. Else, we'll reserve (256 MB / >>> default_huge_page_size()) hugetlb pages, which comes out to be 128 for >>> the case of 2MB hugetlb pages. >> It's odd that 2M gets better test coverage than 512M or 1G. >> >> Is there really a lot of value in testing 128 2M pages? Would, like, 2 already >> be good enough? > > Yup, seems like keeping 128 pages is not adding an extra value. I'll go > with 2 hugetlb pages to test both pinning within a hugetlb page and > across the hugetlb boundary. This would make things a lot simpler. Thanks! -- Cheers, David