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 222C8CA5FA1 for ; Tue, 29 Sep 2026 08:38:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 09DE56B00A5; Tue, 29 Sep 2026 04:38:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 075866B00A6; Tue, 29 Sep 2026 04:38:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id ECD356B00A7; Tue, 29 Sep 2026 04:38:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id C24596B00A5 for ; Tue, 29 Sep 2026 04:38:43 -0400 (EDT) Received: from smtpin28.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id C90B7A03D3 for ; Tue, 29 Sep 2026 08:38:42 +0000 (UTC) X-FDA: 85266148884.28.D253976 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf09.hostedemail.com (Postfix) with ESMTP id 19921140009 for ; Tue, 29 Sep 2026 08:38:40 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=YuvrMQGR; spf=pass (imf09.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=1790671121; 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=VVg9tIviq7YUO40JFcy0O8SZzEsGUatvPj+P4Q6Op00=; b=rTzScx69M4g3Dim+l+RAz1qO+xSUrlMg6JTryn6KYKkGqcEljc6fATZ+tvjqh7cCilhp2O sDIu6KuUYDk/J3peiHvZjnwSsIUcNivoQNgXaolFg0SkqsF30E1MpJNo0kMjin5ifd1L/E J8aZdbWFlciFjGWw6p6AN2Nzwjflkf0= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=YuvrMQGR; spf=pass (imf09.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-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790671121; b=OYvtfbGLnpjcMfdXpviWMt7YufcbQgaZyfHG8RtmiJQvlkftt8QF0DsbmzOmXRksJ1bayN sE48PLwLxqQHg0Q/H8eVJEdyUcTcDkSXuH7FpkMHQ+7VqDSyWcpp/ibY1uDjrYZ26yPgld jtbxWZO9JqmIyC9WPWnYz4Fa1onc7ts= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id A313E60A5A; Tue, 29 Sep 2026 08:38:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 70DB81F000FF; Tue, 29 Sep 2026 08:38:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790671120; bh=VVg9tIviq7YUO40JFcy0O8SZzEsGUatvPj+P4Q6Op00=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=YuvrMQGR50vF5/C2Pg7JH9fh8I3EySZ3ClfQ0UCUAC/lb+wXF83p+bET0Xjy49Ztq qLbOXalNS++fdnEy1tIhAyF+NhGI2w17UPRdB5Z8Tdh/uauwHCrBpCeZCNyt72qQvO JnJSe3aaq7goVO8r2GtwMB7zipImZqkUulC/maBWAUmfmxc3udncoocfG5yH+c3Wtk HkdiDBY1VRaSt4lhe//G/ybXxW+IbR7XtROxlnGFy8t6pR8299AtpvzgxB4MOr2ELA csROmrqXiJhvw7kiNnpNobHnbwwou/qWJ0F5LRqxaphudXR7ZaCzlbbxTU102XQDvp uJLqoNbJF+CEQ== Message-ID: <447e0be9-836d-4324-9a36-77f8a0cbecf9@kernel.org> Date: Tue, 29 Sep 2026 10:38:33 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/2] kselftest: mm: fix intermittent failure khugepaged test To: Yeoreum Yun , Zi Yan , Baolin Wang , "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 Cc: Andrew Morton , Shuah Khan References: <20260923-fix_khugepagd_fail-v3-0-b387e92fe1a9@arm.com> <20260923-fix_khugepagd_fail-v3-2-b387e92fe1a9@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: <20260923-fix_khugepagd_fail-v3-2-b387e92fe1a9@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 19921140009 X-Rspam-User: X-Stat-Signature: ixu33wweonstkdsrydrmmupjotrp7bkx X-HE-Tag: 1790671120-929584 X-HE-Meta: U2FsdGVkX19VgwwGtKG1oTMF2yRrYKPyS/uA8aRO/vrYuPlOnQjnY2xM9U5RQb2wgTosotokggAEZtKxbndw7GfD8swz5ACpzjv5WcWm3SLSFlPVgEhcsaeWvqiQS336vqCXBkKzjC1fdkf51cPXIXFSpHFn/glA3qnoVIfSc9ecM41n/WEDE9kDFIXjPJTbgC06VWwisnBsLWMrxCHLC10newudILZ0dJaHGUEbSjNDbZ0oBgLzdwuClRz3zH1rHPo4uihX7P6gsU2sUYJ/pgaEDKVunvR/R7Xdf5aEb826kecTeNtGXPqqmaeTuCjYJO5troVsnv79r9YSxPgtDhylQ3XdelAF3UEzhATVnPIrH+YiElzbWHiedwqiF4rMaLlPjsXAYhSbFbrShO/VraVV8mSKhHDDaCFy5zaJ15SfOA+/xjYJfHLwhgvACNwcBgby5WMcDN0FTcw/wDYkeXzK2xeijMiUgtC5htoaON3c7ea64jadvNlO3lWe+zTJt8L+kTatzjJqlDU+dNuXHaFk5iF+AoZFoi50Tnp8UnDdm+7qnGlpeycFnom/mbX23j3VtHVUnXyq5DSTzmSm50R/4NqMvvdrbEE+aQQE2uCNRMRKRltd7oJHxQuyOhKIFaaoR8aPiCKWfAgYmW+ydt7U9Hf6l479saeOzGZKkQWLo6g98QzqfouorthSco70w12BOV+dIBaC/0n5wSZSmKz+NsOxFjp255rF9DKVVuPZCMStNI5xa1PqMWhkrKT6kou7LUr4xK2lnzng/RnSVhFDTrFFa5ns66ooGR35iRKPq5Micx0bSGm/xhFHsF3iUo0MEebVJTzq46NjVTO+yNEmV+p5PG9GxMNX9hfJmFpGLpveCIKH1hDT6js654yVjB+u3ZlX86lCBdmFrYVg7B2ToTluOTsoaMQy8nbzTVn1Wlfl49cizk/PVtOKvgXD288ZOvSuhET15pJ6IQI 19aKr8Gk obw7X43Aig+5wSPDxvbKHc2l6fsba2dbafBUNH9FHx8sLOcFnO4dNew/qYs7TC0f7KNsw+H3ou4xoDeivOZIQmiBda5wKIDz+FyyQ+eToAZSlTOWiAgtkLWYMu19oR8O1zv2wZjUc8NpWUBWs/B2wsf2zWAw/8aI6/s/4O2EYc/tpEtBm0S4YrIUZPsUKd0rKNmcMkx1Edkzlndb7XQS3j76sAh8mMIARF6ZyVTHoNwilY92SuKbsnB7I/KI2TtYpllNuBFo2Y/WpZ7dtsHAf9kia9KRIdDzfRQNP0NwLTYFxvn/YniYH/hXuNmB8oCCdrYU5nufVxs3jkipSCs2WS1nzDA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/23/26 17:29, 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. > > Reviewed-by: Baolin Wang > Tested-by: Baolin Wang > 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 2aa7c9197158..b0cb02bf1a73 100644 > --- a/tools/testing/selftests/mm/khugepaged.c > +++ b/tools/testing/selftests/mm/khugepaged.c > @@ -618,6 +618,9 @@ static bool wait_for_scan(const char *msg, char *p, size_t len, > usleep(TICK); > } > > + if (is_anon(ops)) > + madvise(p, len, MADV_NOHUGEPAGE); > + Any reason we just do that unconditionally? After all, we set the madvise(p, len, MADV_HUGEPAGE); unconditionally? -- Cheers, David