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 A308BC61DB9 for ; Fri, 28 Aug 2026 09:39:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A6F516B008A; Fri, 28 Aug 2026 05:39:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A478D6B0092; Fri, 28 Aug 2026 05:39:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 987146B0095; Fri, 28 Aug 2026 05:39:28 -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 71B006B008A for ; Fri, 28 Aug 2026 05:39:28 -0400 (EDT) Received: from smtpin11.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 0806E1A02AD for ; Fri, 28 Aug 2026 09:39:28 +0000 (UTC) X-FDA: 85150180416.11.108E62D Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf04.hostedemail.com (Postfix) with ESMTP id 5D9F540007 for ; Fri, 28 Aug 2026 09:39:26 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=Sto3diAR; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf04.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787909966; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=LcwtPFDsGrgdCaDCg66fqoG97Ouh7ZMZoj1sJOxY13o=; b=PxbBZS7BTb3ivcTGHzwtdjxFkN/mHWVnBaxzxx23WCKRyZZ9XVdqBGt0t2dDU+mn3LuqwY Rm1JxbqwZZ7UJZV6de57P1hMDQ95l6zBY1K1AbrSteRPKL0i0joEJbD4xhUzL5iFAFr/9t xbVeIt0xC4A03Qu34AXwLk4P+vO+WB4= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787909966; b=bTtwETFEoD5HE2F9kP0xRrdzuTLml7LC72I+SzfhFMRXiY3TpLANGuwag+Z+MscNTuopZy HMmcFzBCxTyz/D3u8wpnHtewAFxjP0C6K5//3LTwSuONTUgDV8QjA8TRlQphl2JdDW8mpv 8ownFdSyqZZTjvb/5/X24p/Ejh4YISc= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=Sto3diAR; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf04.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 8BA4E409EF; Fri, 28 Aug 2026 09:39:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A35EF1F000E9; Fri, 28 Aug 2026 09:39:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787909965; bh=LcwtPFDsGrgdCaDCg66fqoG97Ouh7ZMZoj1sJOxY13o=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Sto3diARgnSgihsBVkQyf2L4hleE9pUpjugWfj7HFQbJ7nIWicQiyg9kl6aXmpQ8B kJhrfTXxUAN2JAtxD2Ng4Bn72SdgEXPHNledJdxXAA8W0TT14DgOOkI8zSdLeLvUV9 czM4iTcmnePZcdrsk1ttZE70YEqa8Qs0oVnjsje2siEQ7nKXk2Bh6gyyr03U4YNTeQ RZSUIvXrf6bCrhIqHpzBiYxdnBXq+9YFYvdVhKeGs9pxX4ubGbe8f96RdSVKJmx86q qLvqHIBzlxmljjNRS2z56YiQ4n3YVKsN0uNnmOm6TdT29XosbKvCeQ90sqqPLXOXlK cIruOBdDZE5Zw== Date: Fri, 28 Aug 2026 10:39:18 +0100 From: "Lorenzo Stoakes (ARM)" To: Yeoreum Yun Cc: Andrew Morton , David Hildenbrand , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Kevin Brodsky , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 1/2] kselftest: mm: prevent random failure of huge page split for khugepaged Message-ID: References: <20260828-fix_split-v3-0-374022586a4b@arm.com> <20260828-fix_split-v3-1-374022586a4b@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260828-fix_split-v3-1-374022586a4b@arm.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 5D9F540007 X-Stat-Signature: yfwb6474eb746bgoq5enhptfbi9yn77b X-Rspam-User: X-HE-Tag: 1787909966-320261 X-HE-Meta: U2FsdGVkX1+6ZfYAc/TNYb1wYYVV/rwolyfkSRJqhuPoLLBgHPy5d/M60Xf5pkIbNiWOTK/apdkLYmHahi4CDg+WT/elhiMzB19iVpL9o+63J0+gcXmZLo5JB+YRfvJb7Lri9NOFMNymbmmXzbxovtNX8K1IOZmU44e/SVI2Pes/qCpydx/qndQKhTH5ez+7NMXo9GJ8SM0dXvsfcQrBIJLo9DynD7bhEiC4hsPnPGzBu7PJPS1kzxlJLP7wM4WvI+1/43JEOnzo2IiisNsoDXvusY+6DX1gR8OzdylZ4I3A676ion4EsbPfv3HpbcKRqB3ZzN7/B/yOwu44EwYAf5+S2kNrZ+8KuOI8s/+JnXjLnQLwHSP3S7bEEF9DxwYyS6ncIxIx9Lm4ZoWQb1COUyvqLEBd1UCTApMxHPfkAl1zgXaON5K92nzhn78xT1aHU7r0YT8/obZZcv94N+0w+ubw9S4X/HHm1C3suDlIm6Ad+2OV9d316F0YM73mSBO8hWgq/zQ39PZAMLwsBLVk7UpvLtQGvlqtPOoxG0ulqeFisOgvpKZLHSCVChOxgHnWZ+vQpM30c8B/w4BzeWlojbvPrWJwmlR4KT1Omp5mtjMq066FB3baeJfi+f1PLCOttxpvL+VImUHbtY/6SqjmyyauHkBXRt1zkWLS478CH8EJzX7TJhISJhaOxZhP7VSTGAb7cGUIuV8KeOj1ZdAmqPLpSDvSJu7g2FA60tk2Ux5mRRXij5twHjk+3HENITUlBvwcGFpOCrr6Bg6GgNcDG2b7q8kw56gIEQf6UDsWbt24ov2OkwUgdN/HtR361Gb0yE7xJyK53AJ4VTgLmK93eLeCBKmIUGzrmjfvN86q2n8xQ+Ia8lg8sXWRY1zty7nzyYbdQsawryBtdzHRVcqbuyBOHZHovDILd7vnzBjI00RrwfhN7i0KT8PBF5LsVLaQG1xlOQMH3C1Xam/a7ax aJQwdqib O5PaXY/wre+2jYM1rzzpU3LWFYwbvZ4P3olCKQPRMGUomzCQod1tqHwU+lX52CjJzR5NJv2mK7ZBeh7vOF3CeS5Cn8CuAGTIjh8c5N89NI+vT7jUFN+MVSB7fuGUFShTpSkZ2vPIe6J1Z8h6us/u6YrAmQdS7LsIYkAk1Nz9Mm8oPU+qcxLPrqzwL1d30okYksq8cWg7FqpUDnmk70UwKkFkHwV1AjYVqWGMqX3tjH7Ael9si8FuOKIpU70SMC0dkqpwZ/+rGec9IXe2E/24sYaxr4YrEdKOJvsCDAt4N4xCEm80vwnX9BTEXKtuRjdLdtAN0Zpv5pmVzlQ3owOrYJMchWg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Aug 28, 2026 at 09:11:33AM +0100, Yeoreum Yun wrote: > There're some random failure for split_huge_page_test when khugepaged > collapses pages into pmd again which had split by the test. > > Prevent the khugepaged's collapses for split page by setting the > mapped pmd-huge-page with MADV_NOHUGEPAGE before split. > > Reported-by: Kevin Brodsky > Reviewed-by: Zi Yan > Signed-off-by: Yeoreum Yun > --- > tools/testing/selftests/mm/split_huge_page_test.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c > index 86a603692826..c718269a291f 100644 > --- a/tools/testing/selftests/mm/split_huge_page_test.c > +++ b/tools/testing/selftests/mm/split_huge_page_test.c > @@ -180,6 +180,10 @@ static void verify_rss_anon_split_huge_page_all_zeroes(char *one_page, int nr_hp > if (!rss_anon_before) > ksft_exit_fail_msg("No RssAnon is allocated before split\n"); > > + /* Prevent khugepaged from collapsing the pages. */ > + if (madvise(one_page, len, MADV_NOHUGEPAGE)) > + ksft_print_msg("madvise(MADV_NOHUGEPAGE) failed\n"); This should probably terminate the test no? There's no reason to expect this to fail and it's better to fail then to risk a flake :) > + > /* split all THPs */ > write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, > (uint64_t)one_page + len, 0); > @@ -227,6 +231,10 @@ static void split_pmd_thp_to_order(int order) > if (!check_huge_anon(one_page, 4 * pmd_pagesize, 4, pmd_pagesize)) > ksft_exit_fail_msg("No THP is allocated\n"); > > + /* Prevent khugepaged from collapsing the pages. */ > + if (madvise(one_page, len, MADV_NOHUGEPAGE)) > + ksft_print_msg("madvise(MADV_NOHUGEPAGE) failed\n"); > + Same comment as above, also since this is a repeated pattern, I think it's worth abstracting it like: static void madv_nohuge(char *ptr, size_t len) { if (!madvise(ptr, len, MADV_NOHUGEPAGE)) return; ksft_exit_fail_msg("MADV_NOHUGEPAGE failed, err=%d\n", errno); } > /* split all THPs */ > write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, > (uint64_t)one_page + len, order); > @@ -313,6 +321,10 @@ static void split_pte_mapped_thp(void) > goto out; > } > > + /* Prevent khugepaged from collapsing the pages. */ > + if (madvise(thp_area, thp_area_size, MADV_NOHUGEPAGE)) > + ksft_print_msg("madvise(MADV_NOHUGEPAGE) failed\n"); > + > /* Split all THPs through the remapped pages. */ > write_debugfs(PID_FMT, getpid(), (uint64_t)page_area, > (uint64_t)page_area + page_area_size, 0); > @@ -542,6 +554,9 @@ static int create_pagecache_thp_and_fd(const char *testfile, size_t fd_size, > ksft_test_result_skip("Pagecache folio split skipped\n"); > return -2; > } > + /* Prevent khugepaged from collapsing the pages. */ > + if (madvise(*addr, fd_size, MADV_NOHUGEPAGE)) > + ksft_print_msg("madvise(MADV_NOHUGEPAGE) failed\n"); Obviously same comments re: this and above > return 0; > err_out_close: > close(*fd); > > -- > 2.43.0 > -- Cheers, Lorenzo