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 3D756CA5FA5 for ; Tue, 29 Sep 2026 08:47:02 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 42F3D6B0092; Tue, 29 Sep 2026 04:47:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3DE796B0099; Tue, 29 Sep 2026 04:47:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2D4D36B009B; Tue, 29 Sep 2026 04:47:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id ECFD96B0092 for ; Tue, 29 Sep 2026 04:47:00 -0400 (EDT) Received: from smtpin27.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 6920712045C for ; Tue, 29 Sep 2026 08:47:00 +0000 (UTC) X-FDA: 85266169800.27.2EA775C Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf28.hostedemail.com (Postfix) with ESMTP id B1E7CC0007 for ; Tue, 29 Sep 2026 08:46:58 +0000 (UTC) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=J4HrEAKV; spf=pass (imf28.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=1790671618; 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=Zw3PvTa683KVYIMGi5I0/G6E2FcL9VbXGIRm3XwUYgE=; b=U9NtT7egug3RYvQuk3f49EYt5lu1+X3y5c/k02HCMBZrFNOuf6nbq/p8GijXoAjTLjwmA+ x3oG/KZZvfgU2RCPe3TQJWw9VaJ0pJv1zpY7nVL4xr8hhzfpLp8Nt6pZAqApYSkC5jPNNE b9lN3IPBzEsvJdfNq8B8WiByDxD07Do= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790671618; b=D1LrgmUb2JY5b0F5OW9Pf5HBqIpeTTR/X/ip7XV6b2sy/pTDOW0iEnVu426KgLGXWO/f/M Lnb6j5RSEXdxH2VxhYuHERi0M208GpFvCHb5NBIHbKviJuutMcYNvkU0UPr38ERlXC3jh2 Xvc0lNoIpxz8LKYnsApntK51NpWVAbc= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=J4HrEAKV; spf=pass (imf28.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 78BAF60A62; Tue, 29 Sep 2026 08:46:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 88AAE1F000FF; Tue, 29 Sep 2026 08:46:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790671617; bh=Zw3PvTa683KVYIMGi5I0/G6E2FcL9VbXGIRm3XwUYgE=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=J4HrEAKV7fVngd4o2/Ww4OltHMAUpPp05AJ91lFOkP4iBmU3ynDWftgqrgzVnym7b TMGwzEza5jTsZHNLGPI/JYJIeRf8VA5GaolSfbUsueVNI7H6D+tSC2pNsNI2Q/Hpb9 2rNj8wyYHaQL+cqCNeeqlaVOYdQq4LF/4B+iF/UnhNhLGQazn9FaeUSagyQ+efz6ca 9SDmVZzUw4TdW1J4oiMLpq6VW34PCxJw6EqVW54T928w75pUmoWPshHHp9w5y9Jlky VRPDOA9L+erYvS5R/LDr4nKRxx9ge9PCpJnhjr7lfkzOz0ZdygFPfkyXUiFS4hNcg6 lPOCYRSrNsRPg== Message-ID: Date: Tue, 29 Sep 2026 10:46:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/2] kselftest: mm: fix intermittent failure khugepaged test To: Baolin Wang , Yeoreum Yun , 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 Cc: Andrew Morton , Shuah Khan References: <20260923-fix_khugepagd_fail-v3-0-b387e92fe1a9@arm.com> <20260923-fix_khugepagd_fail-v3-2-b387e92fe1a9@arm.com> <447e0be9-836d-4324-9a36-77f8a0cbecf9@kernel.org> <84d3a9f5-4bfb-4f5e-86ad-ac8fb896d885@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: <84d3a9f5-4bfb-4f5e-86ad-ac8fb896d885@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: B1E7CC0007 X-Stat-Signature: p8j7dhwr6hkykq8qk33a44783e89tnh7 X-HE-Tag: 1790671618-216288 X-HE-Meta: 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 8R0igxWt 03THGQELy8Qh+SLoJFsou5XtoaEuaDtIST3kFXCR4TuoNB3XUlYBW4ldztIxFCleV/BjcH7RqW30yFZNNSmLek7Iqm/ZLJ1spsB9SIKx78LDE4BnoDnOcjYJKgQXyMqsLAv34xMbVSQ0W/qsTZ8wh9mXCWDrVesQsTdO6bsWOyRoRus6I/eembVq2O2zGGF4le9kkEIQfiT4TDpyp2RTGDL8aJb8Oc9TNK4MkFGE4iNlJvolJRG4nDkbmOvcYuvZXSJSHI1elPUaB2TYBa1n3Z9oJMllJyR5rJPx7TNawXbnp2JBnraegyYw+Jwy5hOKooFFlo9soC+bBwAXGF7xkoOSXDpR5yLbAmWmkRMVNawgq9Kxq8t+42rhA3g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/29/26 10:43, Baolin Wang wrote: > > > On 9/29/26 4:38 PM, David Hildenbrand (Arm) wrote: >> 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? > > Although it's a bit messy, as I mentioned before [1], unconditionally setting > MADV_NOHUGEPAGE will break shmem testing. Maybe add some comments. Ah, thanks for clarifying. The problem really is that we cannot undo a MADV_HUGEPAGE (give me hugepages) cleanly. We can only go to the other extreme (no huge pages). Yes, let's please add a comment describing why we limit it to anon. -- Cheers, David