From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 64D91C79FB6 for ; Wed, 9 Sep 2026 17:04:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7564D6B0095; Wed, 9 Sep 2026 13:04:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 72DAB6B0096; Wed, 9 Sep 2026 13:04:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 61CAB6B0098; Wed, 9 Sep 2026 13:04:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 4138D6B0095 for ; Wed, 9 Sep 2026 13:04:14 -0400 (EDT) Received: from smtpin03.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 35DEA1A02B1 for ; Wed, 9 Sep 2026 17:04:13 +0000 (UTC) X-FDA: 85194846786.03.238E2A3 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf02.hostedemail.com (Postfix) with ESMTP id 6DD0A80009 for ; Wed, 9 Sep 2026 17:04:11 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=KL7POgn6; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788973451; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=lkwv44ETJQmXMk/e//8L25kcENQTJgfQl/TVfQuISwc=; b=hCvhkLG9ly7f1uUGy4JZBisnKtM7+Gcy6EyDN6vI5M43Zob6tayW7XGixQ0gy/McdD6IJ7 t//x/HelDBwifKwvDWRn8rRIBuheguVkKhPtgVT/ROuvpQNAdipg2pVtt0DhFQYJb1oMUC D8UOxQFqyO4UrqsCFAp2bODv7Tin/UE= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788973451; b=DJph3hbgfekBVcjmX9cEOIEoXE8cKo96WXuunFze0sm8IZgUWtKZonWlqwim1jOejHwCfq WjPLvIoQQCGPZHvaLCqT/r4ZeuSVmWV7M3aU3e3dXzkPEMELF/aRCmSoNcz0Uk/bIifLdi KSWDNI12g45eUP4MzkUtQiWtU4Gcqg0= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=KL7POgn6; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id DEA1C6020A; Wed, 9 Sep 2026 17:04:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3CA921F000FF; Wed, 9 Sep 2026 17:04:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788973450; bh=lkwv44ETJQmXMk/e//8L25kcENQTJgfQl/TVfQuISwc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=KL7POgn61am+C0j55B/xe9I829GKFJnbqWM4Sc/9uo0gsewY7R4uvjHdTY0G8JyPr 6s4jQGnZWL5sM9uC2hCRrnpFWpXaFpxgmfIpQLQj0r7sxzWAzGJa3hJdqToLmJ0u7n tRy8znb7vuPr1VTD6e+80AZIlRogFWzwb4pLcfqNoIzli/IEbE/4JkxtDsTf9KkcWh W/omgFBeAIX95D1F4PMYJq/8fyPFdUMvwRXjemECj2YM927HdL21W5BCrdwt0/JajC sYugAQRUycBh3DyaZ8TBz3341pDD48IrCkDOeQ4fRcRr3xh0APtnsMjoI9ZyAHdHS7 wWwZtLa2i6Xqg== Message-ID: Date: Wed, 9 Sep 2026 19:03:59 +0200 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: <5e0b9365-cbac-4f2d-b915-85edf3093508@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: 1w4yn6iud1yg6y8m1cu455oxpur8911j X-Rspamd-Queue-Id: 6DD0A80009 X-HE-Tag: 1788973451-754908 X-HE-Meta: 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 fzqUxiI7 LWtG5hmupTuQwAYlKFK9cAYAkI1L6Pmb9IeuhlAxt0FDoPKIO9lvnueuYgvjrpt2/Re+7CWn9tlAU/KqzVEI6dfVzpR+BfEahCzoJz4HyQaJkqkc6DPZm1IRhtwswg3nBXKUzVOgFi62E66QAtjeNw8z5ZbGYC7N2/VBgc/aIRFlT2D/blLZJdLN3xPl6MdcLhWqCImGy3pOydKnKLp8w/Dgk7/q5mrzp5SSm/IIKIHxFIrDE4U3YS8wh/oi9W3s7rPvp Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >> BTW, I was wondering what it would take to: >> >> 1) Turn mm/gup_test.o into an OOT module (would we need more EXPORT_SYMBOL_GPL? >> EXPORT_SYMBOL_FOOR_MODULE ?) >> >> 2) Move it to tools/mm/modules or sth like that. >> >> 3) Build it with the selftests etc >> >> 4) Remove GUP_TEST >> >> 5) Try insmod'ing it from the tools+selftests that need it. > > 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. >> >>> +int main(int argc, char **argv) >>> +{ >>> + char *file = "/dev/zero"; >>> + int fd; >>> + >>> + fd = open(file, O_RDWR); >>> + if (fd < 0) { >>> + ksft_print_header(); >>> + ksft_exit_fail_msg("Unable to open %s: %s\n", file, strerror(errno)); >>> + } >>> + close(fd); >> >> >> I'm confused. Why do we have to open+close /dev/zero? > > 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. > >> >>> + >>> + fd = open(GUP_TEST_FILE, O_RDWR); >>> + if (fd == -1) { >>> + ksft_print_header(); >>> + if (errno == EACCES) >>> + ksft_exit_skip("Please run this test as root\n"); >> >> Wouldn't we want to fail here? > > 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! [...] >> >> BTW, why are we using HUGETLB_TARGET_SIZE instead of just using the >> default_huge_page_size()? > > 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? -- Cheers, David