From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-101.freemail.mail.aliyun.com (out30-101.freemail.mail.aliyun.com [115.124.30.101]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 721F0610D for ; Mon, 9 Jun 2025 06:36:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.101 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749450968; cv=none; b=g4bS89PPGSh/UWfRvUtKnX1n4RgVZifdafLWUwNo2kcaFnouu+p4gdDuTtRcS5W13XkJh4+PJc8814w8S8CmSHHTCvVkIKn8D0ZuMb1366yxCRY36Y4yovEhRTSDEG6zapRTkPJAk0cOmfCV/sBsooU7oI1Fuy0ulIZq0aYxGYQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749450968; c=relaxed/simple; bh=DLAL88a4FC4DPY+ofxZZ0wDlZVzrTRO/IiXf9Ts8Cog=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=sNRgBh9GRXLXqrYh9IG8/EIo4JGa95nDo9bEvHMy9mp/eHmOfI21Bh+5Ppdd7gdvEolZP0h6Hcbke5WY0hPFIBG0dBJtl7UY7dsWF/EPgSDzsnhgx1YVnH2XBXAMJF64J26zC3Qgk1ADAURk3lbSnU8955xfaeKDQMcxSibvZHE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=ryv8C36+; arc=none smtp.client-ip=115.124.30.101 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="ryv8C36+" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1749450962; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=NkGvTMFQQCyEpDTkBUCTdfjzDh5e8ly4M3dbCb1Avtk=; b=ryv8C36+uYqYDotOByFHSNPNhnMLI/7ZU2c/xWTDCNJ97/gJt990xr+NIXlwefhLiUC6iRfH2oVwx2KmEhCqq9IRSPobGlGDHA3jlCkBvd0u8NDG81MQxsZdh3GXQO8+ZJSwzRXNEjRwpDveplm0/g5wC2X7ORfh7HdP8Nnp0C4= Received: from 30.74.144.144(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WdM8f3A_1749450961 cluster:ay36) by smtp.aliyun-inc.com; Mon, 09 Jun 2025 14:36:02 +0800 Message-ID: Date: Mon, 9 Jun 2025 14:36:01 +0800 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 v2 1/2] mm: huge_memory: disallow hugepages if the system-wide THP sysfs settings are disabled To: Nico Pache Cc: akpm@linux-foundation.org, hughd@google.com, david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <8eefb0809c598fadaa4a022634fba5689a4f3257.1749109709.git.baolin.wang@linux.alibaba.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2025/6/9 02:37, Nico Pache wrote: > On Thu, Jun 5, 2025 at 2:01 AM Baolin Wang > wrote: >> >> The MADV_COLLAPSE will ignore the system-wide Anon THP sysfs settings, which >> means that even though we have disabled the Anon THP configuration, MADV_COLLAPSE >> will still attempt to collapse into a Anon THP. This violates the rule we have >> agreed upon: never means never. >> >> Another rule for madvise, referring to David's suggestion: “allowing for collapsing >> in a VM without VM_HUGEPAGE in the "madvise" mode would be fine". >> >> To address this issue, should check whether the Anon THP configuration is disabled >> in thp_vma_allowable_orders(), even when the TVA_ENFORCE_SYSFS flag is set. >> >> In summary, the current strategy is: >> >> 1. If always & orders == 0, and madvise & orders == 0, and hugepage_global_enabled() == false >> (global THP settings are not enabled), it means mTHP of that orders are prohibited >> from being used, then madvise_collapse() is forbidden for that orders. >> >> 2. If always & orders == 0, and madvise & orders == 0, and hugepage_global_enabled() == true >> (global THP settings are enabled), and inherit & orders == 0, it means mTHP of that >> orders are still prohibited from being used, thus madvise_collapse() is not allowed >> for that orders. >> >> Reviewed-by: Zi Yan >> Signed-off-by: Baolin Wang >> --- >> include/linux/huge_mm.h | 23 +++++++++++++++++++---- >> 1 file changed, 19 insertions(+), 4 deletions(-) >> >> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >> index 2f190c90192d..199ddc9f04a1 100644 >> --- a/include/linux/huge_mm.h >> +++ b/include/linux/huge_mm.h >> @@ -287,20 +287,35 @@ unsigned long thp_vma_allowable_orders(struct vm_area_struct *vma, >> unsigned long orders) >> { >> /* Optimization to check if required orders are enabled early. */ >> - if ((tva_flags & TVA_ENFORCE_SYSFS) && vma_is_anonymous(vma)) { >> - unsigned long mask = READ_ONCE(huge_anon_orders_always); >> + if (vma_is_anonymous(vma)) { >> + unsigned long always = READ_ONCE(huge_anon_orders_always); >> + unsigned long madvise = READ_ONCE(huge_anon_orders_madvise); >> + unsigned long inherit = READ_ONCE(huge_anon_orders_inherit); >> + unsigned long mask = always | madvise; >> + >> + /* >> + * If the system-wide THP/mTHP sysfs settings are disabled, >> + * then we should never allow hugepages. >> + */ >> + if (!(mask & orders) && !(hugepage_global_enabled() && (inherit & orders))) >> + return 0; > Hi Baolin, > > Thanks for making this change so we enforce the 'never' being never > rule. As others have noted, this statement is hard to read-- is there > any improvements we can make to the readability as Lorenzo suggested? Yes, will do in next version. > Either way, I've tested this and the functionality works as intended. > > Tested-by: Nico Pache Thanks for testing.