From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0A0F1485CEF; Fri, 25 Sep 2026 12:10:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790338253; cv=none; b=b6CV6a7PypCGpcm12fh3sOaEw0fSb4+0fcAYdrXh2uoagJemfXIJp3cwgENU2wsyT+NY0J5SLVhCPkjUt6lXDfnwqDnWbEJmWsd+33yh31kbNUVku41iSAGrtg7+J9CdtF6n4vIFhw3/IHEzF3rN3dpc8hjuH04IIC5BwaNy44c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790338253; c=relaxed/simple; bh=NEYUebGz1uDI7Npr1A5moQGPlxhm/IrhMht840u7NQc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UZt0s9nmMQkPP2fiVX/qoBgeemXEXDYDEHygjUNUsvOH43Dvw4oC6UIq+XaKGu2mD0n7guhi6HW9P8G9wzSOz0XFqCoJc43K2YTXkuv4thkmvrd0zGi/HwfYpSclTZtGs05fa/Np5pEf4sCBex5xOLf2NWw7mkiC2pc93VlwfEg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=Er6Bps5u; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="Er6Bps5u" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 44A1D1688; Fri, 25 Sep 2026 05:10:46 -0700 (PDT) Received: from [10.164.19.84] (a081061.arm.com [10.164.19.84]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3E67F3F86C; Fri, 25 Sep 2026 05:10:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790338249; bh=NEYUebGz1uDI7Npr1A5moQGPlxhm/IrhMht840u7NQc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Er6Bps5u28i6dwAxosn/pPKCYRMfwt73pA1zVb2TfE6fj8cf/A5kmRyUPZv2+ciQ2 j1TBYB48z5UXdNCINevu8QF8PkZUhtuiQ5Pn2Ro5HP7OJI2hN54ESlSYvVJvlz7uGi wFpSLMRb/mEw4Rs/Nt2uP+2z8wwx6+vbNNgTL11g= Message-ID: <07f94688-55ed-407a-a11a-78a4feedf5e2@arm.com> Date: Fri, 25 Sep 2026 17:40:41 +0530 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 v8 1/4] kselftest: mm: prevent random failure of huge page split for khugepaged To: Yeoreum Yun , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , 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 Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260924-fix_split-v8-0-cba7359d882a@arm.com> <20260924-fix_split-v8-1-cba7359d882a@arm.com> Content-Language: en-US From: Sarthak Sharma In-Reply-To: <20260924-fix_split-v8-1-cba7359d882a@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/25/26 12:41 AM, 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. > > Suggested-by: Kevin Brodsky > Suggested-by: Lorenzo Stoakes (ARM) > Reviewed-by: Lorenzo Stoakes (ARM) > Reviewed-by: Zi Yan > Acked-by: David Hildenbrand (Arm) > Signed-off-by: Yeoreum Yun > --- > tools/testing/selftests/mm/split_huge_page_test.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c > index c5d96a4b1db3..ef4058662b91 100644 > --- a/tools/testing/selftests/mm/split_huge_page_test.c > +++ b/tools/testing/selftests/mm/split_huge_page_test.c > @@ -108,6 +108,18 @@ static char *allocate_zero_filled_hugepage(size_t len) > return result; > } > > +static void disable_khugepaged(void *addr, size_t len) > +{ > + /* > + * Disables khugepaged from collapsing THPs in range, existing THP Should it be "collapsing pages in range into THPs" instead? > + * pages remain. > + */ > + if (!madvise(addr, len, MADV_NOHUGEPAGE)) > + return; > + > + ksft_exit_fail_msg("MADV_NOHUGEPAGE failed, err=%d\n", errno); I feel a ksft_exit_fail_perror() would be better here, since it will automatically print strerror(errno) as well. Still, it is not something that should require a respin of its own, so if you plan to respin for some other changes, you might fold these changes in as well. Rest looks good, so: Reviewed-by: Sarthak Sharma > +} > + > static void verify_rss_anon_split_huge_page_all_zeroes(char *one_page, int nr_hpages, size_t len) > { > unsigned long rss_anon_before, rss_anon_after; > @@ -120,6 +132,8 @@ 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"); > > + disable_khugepaged(one_page, len); > + > /* split all THPs */ > write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, > (uint64_t)one_page + len, 0); > @@ -167,6 +181,8 @@ 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"); > > + disable_khugepaged(one_page, len); > + > /* split all THPs */ > write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, > (uint64_t)one_page + len, order); > @@ -215,6 +231,8 @@ static void split_pte_mapped_thp(void) > goto out; > } > > + disable_khugepaged(thp_area, thp_area_size); > + > /* > * To challenge spitting code, we will mremap a single page of each > * THP (page[i] of thp[i]) in the thp_area into page_area. This will > @@ -482,6 +500,7 @@ 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; > } > + disable_khugepaged(*addr, fd_size); > return 0; > err_out_close: > close(*fd); >