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 2875DC624D3 for ; Wed, 2 Sep 2026 15:16:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3A87A6B00E2; Wed, 2 Sep 2026 11:16:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 37F8F6B00E5; Wed, 2 Sep 2026 11:16:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 295F36B00E6; Wed, 2 Sep 2026 11:16:38 -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 0B6616B00E2 for ; Wed, 2 Sep 2026 11:16:38 -0400 (EDT) Received: from smtpin14.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id A474E12025E for ; Wed, 2 Sep 2026 15:16:36 +0000 (UTC) X-FDA: 85169173992.14.D044EEF Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf11.hostedemail.com (Postfix) with ESMTP id DD3A140011 for ; Wed, 2 Sep 2026 15:16:34 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=oXZ31SXF; spf=pass (imf11.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@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=1788362195; b=tdCyUvk6kzdNGxXf4Ozrpx0kniG7OFyFqU4e1ncbtlyGvNkjbL9/NYnC5nf+CPRKkrcokj 0aDfy0uuwckvWK0ivIpapxt1tDlw0zQw9cjj9UDlCC0RXXNe7zd9muUuuxMLR6X8VnY9+4 PIheMvwsdaVag9mF9+roEWlSnt+VcnE= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788362195; 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=+rQ7EcvByoK4DZLWp9NFal1KQajz/7yVumEJS4KpGI0=; b=FduDcoCymAEesfFX9Zp66okGQIn650OieXOVZyFsB1ogYoVnZBM4D/P+GYezn6hrwAMYbN BnjiHfqZ09MayecTNhjDtZ0hu/NXmFqOq4F5zRo5dXHF21ModrQpJTYdkJ8K/L8PeS7T56 EB0Bjq92mnQgtvmLWWKCOen7wy4hzIg= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=oXZ31SXF; spf=pass (imf11.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 0896A41632; Wed, 2 Sep 2026 15:16:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3EE8D1F000E9; Wed, 2 Sep 2026 15:16:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788362193; bh=+rQ7EcvByoK4DZLWp9NFal1KQajz/7yVumEJS4KpGI0=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=oXZ31SXFQeKa7qgBq6JYStg/0PJqGBLSHHohhrgz32lgk+c/BNuaqzvv3VETRiUog J6ypkPHFnqifKoYj7ko/uPMsMQt8oDeQ6tkbdn2/Idw8/3gHz812zI0Sq5PIwz5Tr0 qK89oRDxGrxDas/68u3QtmLXYmUVsIlXmgIt0oBtSo4/cMHq7pwdCs0F6mMY9ktWez g1W5VS5jLlM2mpaBbVds1crSoi5BGSXqP4RZbNXpHr4qjTL6BQCtpKkZbbj+fEgsd0 pBjCEhNDU7Bu6CrdoLsCTBxUmNyiFaCoo3Y7GYFP42ghQ/9UeLsrUiuEGg8ftDgQ7j cjSH4pHVNNRKA== Date: Wed, 2 Sep 2026 16:16:26 +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 v4 1/3] kselftest: mm: prevent random failure of huge page split for khugepaged Message-ID: References: <20260902-fix_split-v4-0-85f03905f7b1@arm.com> <20260902-fix_split-v4-1-85f03905f7b1@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: DD3A140011 X-Stat-Signature: csz3c14o5z4p8z7q6b8rfrzto7gqi6de X-HE-Tag: 1788362194-888584 X-HE-Meta: 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 jvYqHaHv IqAKhySwnvzUfGs82kXAigig+epDAiWnr3N+iDcNG1tWC/VEKHVmuGokKguAFEFuWswgJaI3pdLgdqcJUUSy+6fzj3MchteiTFL28H1Xrljk8hcJxnBmFXFgJjL2gBcx+AmtVW0uMKWUSYEewwAXj2MFsFD5yieQLDXa8AftbIJR9WhqbtHxQAJQ9M5GvEL6zy4daWewRJ6py88WfkRZ51rrK9Hrphw7V0oS9/iM4mNimK9xkFi1Bei5JRcph7BI00hMk Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Sep 02, 2026 at 04:15:17PM +0100, Lorenzo Stoakes (ARM) wrote: > Maybe call it disable_khugepaged() to make it explicit that's what this is doing > rather than eliminating any THP pages in the range? > > > +{ > > Maybe a comment here like: > > /* > * Disables khugepaged from collapsing THPs in range, existing THP > * pages remain. > */ > Oh and with these changes you can delete all of the: /* Prevent khugepaged from collapsing the pages. */ Comments below as they will be implied by the name and explained by the comment :) Thanks! > > + if (!madvise(addr, len, MADV_NOHUGEPAGE)) > > + return; > > + > > + ksft_exit_fail_msg("MADV_NOHUGEPAGE failed, err=%d\n", errno); > > +} > > + > > 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; > > @@ -180,6 +188,9 @@ 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. */ > > + madv_nohuge(one_page, len); > > + > > /* split all THPs */ > > write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, > > (uint64_t)one_page + len, 0); > > @@ -227,6 +238,9 @@ 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. */ > > + madv_nohuge(one_page, len); > > + > > /* split all THPs */ > > write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, > > (uint64_t)one_page + len, order); > > @@ -275,6 +289,9 @@ static void split_pte_mapped_thp(void) > > goto out; > > } > > > > + /* Prevent khugepaged from collapsing the pages. */ > > + madv_nohuge(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 > > @@ -542,6 +559,8 @@ 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. */ > > + madv_nohuge(*addr, fd_size); > > return 0; > > err_out_close: > > close(*fd); > > > > -- > > 2.43.0 > > > > -- > Cheers, Lorenzo -- Cheers, Lorenzo