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 24322455635; Wed, 23 Sep 2026 13:54:44 +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=1790171686; cv=none; b=Z2TGgZBZzSj+qr0eVxrV1dxubMfsc1rvTlyZCfG9ShklhdjhATU+TIBpNiyV6RQC3nkhqadJUw/FRGK3BsHkauW4ag534ghZ3mqytQFhkZTOSB0HE19NuZ2Z7IaXrN0K36zAcweKJD9EbahPDhN3oAruL8xa5Mq2w6MAdBvtjS8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790171686; c=relaxed/simple; bh=3xdu8TqqojNI1/L2WgyqebV/A4o3RGXP8uDvwc+LGRA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=af+VwNKTLvuGC7ccU0cjj/8l/Eqg1IEtVT7b9Iqn+OoO3PrGJAvyoZzjpi8NKeidGxB5IWj0Muflh8xYYF9ENleFtNGYuVRO0UD5EfS4glSLByrqQC3G9Qw01cciLhigB9H46TG89/1/p8CcrHuvoF8I9x7cgV/iTHrJh7a1Sj8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nYvHCK00; 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="nYvHCK00" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7F5D41F000FF; Wed, 23 Sep 2026 13:54:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790171684; bh=lV+u7ZikXuhz6S/aX/agfwlx8ZCGacyG0jw47bgroto=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=nYvHCK00gse9lc8Gx/Mov2CNFiG+zwZQHvXDTyOyRVnDEZ7e/j+dBt4VaW492ZGkp hpxR+G1QWZhj0OCGcyUJe3NS+dPfIOz58dyG8LtXFDK+CVfY1Ab9PrVbLAfE0A3Si9 muH/fQOeqkwXuhVgU+lv4cmT03OdPxLxwo8H6Cqb+/WGhsMFI3fPbi5/wG5OjrK/np Gy5y45GHFTQJneDnyD3kQM9yg8Dez91ESmEcAYXsc92m5ei+9Y79Q6cQfeItsn3lud 18hXNzMMc068k6FgYejJd6kei3cViLgDhMmavBGFCShROmYqJ8Ih/IOgqRUkaahO+d 1NG6zA4/bxbqw== Message-ID: Date: Wed, 23 Sep 2026 15:54:34 +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 v2 2/2] kselftest: mm: fix intermittent failure khugepaged test To: Yeoreum Yun , Baolin Wang Cc: Zi Yan , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Morton , Shuah Khan References: <20260921-fix_khugepagd_fail-v2-0-3c2877beef61@arm.com> <20260921-fix_khugepagd_fail-v2-2-3c2877beef61@arm.com> <6cc12fe6-4f2f-47b6-b821-8a507eb80b46@linux.alibaba.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 9/23/26 12:54, Yeoreum Yun wrote: >> >> >> On 9/21/26 6:35 PM, Yeoreum Yun wrote: >>> There are intermittent failures in collapse_max_ptes_swap() and >>> collapse_max_ptes_shared() when using the khugepaged_context: >>> >>> // while running ./khugepaged -s 2 >>> >>> # Run test: collapse_max_ptes_shared (khugepaged:anon) >>> # Allocate huge page... OK >>> # Share huge page over fork()... OK >>> # Trigger CoW on page 1023 of 2048... OK >>> # Maybe collapse with max_ptes_shared exceeded.... OK >>> # Trigger CoW on page 1024 of 2048... Fail >>> Bail out! Unexpected huge page >>> # Planned tests != run tests (26 != 23) >>> # Totals: pass:23 fail:0 xfail:0 xpass:0 skip:0 error:0 >>> >>> # Run test: collapse_max_ptes_swap (khugepaged:anon) >>> # Swapout 257 of 2048 pages... OK >>> # Maybe collapse with max_ptes_swap exceeded.... OK >>> # Swapout 256 of 2048 pages... OK >>> Bail out! Unexpected huge page >>> # Planned tests != run tests (26 != 17) >>> # Totals: pass:17 fail:0 xfail:0 xpass:0 skip:0 error:0 >>> >>> This happens because khugepaged may collapse the pages before wait_for_scan() >>> is called, causing a sanity check that expects uncollapsed pages to fail. >>> >>> For example, in collapse_max_ptes_swap(), after faulting the pages back in >>> and paging out up to max_ptes_swap pages, khugepaged may collapse them again >>> before c->collapse() is called. >>> >>> To prevent this, mark the VMA with MADV_NOHUGEPAGE after it has been >>> collapsed by wait_for_scan() for anon. This prevents khugepaged from >>> collapsing it again before c->collapse() is called. >>> >>> This failure was observed on NVIDIA Spark with 16KB page. >>> >>> Signed-off-by: Yeoreum Yun >>> --- >>> tools/testing/selftests/mm/khugepaged.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c >>> index c32244b565658..1aad4bb427ece 100644 >>> --- a/tools/testing/selftests/mm/khugepaged.c >>> +++ b/tools/testing/selftests/mm/khugepaged.c >>> @@ -578,6 +578,9 @@ static bool wait_for_scan(const char *msg, char *p, size_t len, >>> usleep(TICK); >>> } >>> + if (!strncmp(ops->name, "anon", 4)) >> >> We usually use the 'if (ops == &__anon_ops)' check in this file to identify >> anonymous test cases. >> >> With that, LGTM. >> Reviewed-by: Baolin Wang >> Tested-by: Baolin Wang > > I think this is merged at mm/mm-unstable already So, I'll send > another patch to change it with is_anon(). Unless it is in mm-stable we can reasonably squash stuff or resend. This shouldn't be an independent patch. -- Cheers, David