From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) (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 024021531C8 for ; Thu, 14 May 2026 01:14:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.132 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778721271; cv=none; b=dz6qWj6CpFgIxqagGrdyDb53mb28twGP+vVMrrtHVKoWRVVi1cy/fH+cTsqtRnoBxUoh4rPrRLtYstsGxs4EDuvzlB9xjdo8PlO1qLgEoIHArJhmBdj1DbTW+dfOfekGwVZ+MtFeZQMl93AKtKc/Wz7VbUOI5UXN4OHSvedJyXI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778721271; c=relaxed/simple; bh=pMZIloyuoai88oVAMR62Gao4xG/zzKM2+3+DFJLyQo8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=EGeNTvZ1SxQto0Nu+tVxEwsMDLnewHFm5KhUmzbSDumPO3CkGjBHe5IhmwABkM2XycMBNyxW9G2cEv/MH0+VL9DMnv1KNGl7EZvcb25ULzJc4MgnxtevXFAQFX3EgsERzsU/4UWZaDw9ePnlNbEDL4cMF0WPQAS8joZJtYmRc+Y= 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=xF8xf+zM; arc=none smtp.client-ip=115.124.30.132 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="xF8xf+zM" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1778721260; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=325Nj4SkWAN2yfmB/v07RmcNNk9MGrt8w7gUkkkxemY=; b=xF8xf+zMJ3Lrcc80dyaB1IhtMSZVFLFpEIei1innUVJpLrkjEmxXFALBANXlYXte1dzfgqdFbkqRaHxPdCPiCXZVSjuzes3UIA9r2EiS+4W1A7DS1BUgq2QGTC9cao8FADu54L/66l0RHqUgbfz3oxOX9/YNDMjgECppR0ilUYo= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037026112;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=21;SR=0;TI=SMTPD_---0X2v5VKl_1778721258; Received: from 30.74.144.136(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0X2v5VKl_1778721258 cluster:ay36) by smtp.aliyun-inc.com; Thu, 14 May 2026 09:14:18 +0800 Message-ID: <972a86e9-3c92-4e90-b02b-e9cdb18f0973@linux.alibaba.com> Date: Thu, 14 May 2026 09:14:17 +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 v4 9/9] mm: thp: always enable mTHP support To: "David Hildenbrand (Arm)" , Luiz Capitulino , linux-kernel@vger.kernel.org, linux-mm@kvack.org, ziy@nvidia.com, lance.yang@linux.dev Cc: corbet@lwn.net, tsbogend@alpha.franken.de, maddy@linux.ibm.com, mpe@ellerman.id.au, agordeev@linux.ibm.com, gerald.schaefer@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, x86@kernel.org, dave.hansen@linux.intel.com, djbw@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com References: From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 5/13/26 11:58 PM, David Hildenbrand (Arm) wrote: > On 5/1/26 21:18, Luiz Capitulino wrote: >> If PMD-sized pages are not supported on an architecture (ie. the >> arch implements arch_has_pmd_leaves() and it returns false) then the >> current code disables all THP, including mTHP. >> >> This commit fixes this by allowing mTHP to be always enabled for all >> archs. When PMD-sized pages are not supported, its sysfs entry won't be >> created and their mapping will be disallowed at page-fault time. >> >> Similarly, this commit implements the following changes for shmem in >> shmem_allowable_huge_orders(): >> >> - Drop the pgtable_has_pmd_leaves() check so that mTHP sizes are >> considered >> - Filter out PMD and PUD orders from allowable orders when >> PMD-sized pages are not supported by the CPU >> >> Signed-off-by: Luiz Capitulino >> --- >> mm/huge_memory.c | 23 ++++++++++++++++++----- >> mm/shmem.c | 14 +++++++++----- >> 2 files changed, 27 insertions(+), 10 deletions(-) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 32254febe097..c1765c8e3dc6 100644 [snip] >> diff --git a/mm/shmem.c b/mm/shmem.c >> index a48f034830cd..23893c2bc2dd 100644 >> --- a/mm/shmem.c >> +++ b/mm/shmem.c >> @@ -1840,16 +1840,19 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, >> unsigned long mask = READ_ONCE(huge_shmem_orders_always); >> unsigned long within_size_orders = READ_ONCE(huge_shmem_orders_within_size); >> vm_flags_t vm_flags = vma ? vma->vm_flags : 0; >> - unsigned int global_orders; >> + unsigned int global_orders, filter_orders = 0; >> >> - if (!pgtable_has_pmd_leaves() || (vma && vma_thp_disabled(vma, vm_flags, shmem_huge_force))) >> + if (vma && vma_thp_disabled(vma, vm_flags, shmem_huge_force)) >> return 0; >> >> + if (!pgtable_has_pmd_leaves()) >> + filter_orders = BIT(PMD_ORDER) | BIT(PUD_ORDER); > > Would "disabled_orders" or "unavailable_orders" be more appropriate? Thanks. Better than my naming:) > There is no need to disable PUD-orders, as shmem does not support PUD-orders > (unlike DAX). So you can keep it simpler here. Agree. >> global_orders = shmem_huge_global_enabled(inode, index, write_end, >> shmem_huge_force, vma, vm_flags); >> /* Tmpfs huge pages allocation */ >> if (!vma || !vma_is_anon_shmem(vma)) >> - return global_orders; >> + return global_orders & ~filter_orders; >> >> /* >> * Following the 'deny' semantics of the top level, force the huge >> @@ -1863,7 +1866,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, >> * means non-PMD sized THP can not override 'huge' mount option now. >> */ >> if (shmem_huge == SHMEM_HUGE_FORCE) >> - return READ_ONCE(huge_shmem_orders_inherit); >> + return READ_ONCE(huge_shmem_orders_inherit) & ~filter_orders; >> >> /* Allow mTHP that will be fully within i_size. */ >> mask |= shmem_get_orders_within_size(inode, within_size_orders, index, 0); >> @@ -1874,6 +1877,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, >> if (global_orders > 0) >> mask |= READ_ONCE(huge_shmem_orders_inherit); >> >> + mask &= ~filter_orders; >> return THP_ORDERS_ALL_FILE_DEFAULT & mask; >> } >> >> @@ -5457,7 +5461,7 @@ void __init shmem_init(void) >> * Default to setting PMD-sized THP to inherit the global setting and >> * disable all other multi-size THPs. >> */ >> - if (!shmem_orders_configured) >> + if (!shmem_orders_configured && pgtable_has_pmd_leaves()) >> huge_shmem_orders_inherit = BIT(HPAGE_PMD_ORDER); > > Do we really want to change that? We can just leave the defaults as is, no? Yes, this needs to be handled the same way as anonymous memory. If pgtable_has_pmd_leaves() returns false, but huge_shmem_orders_inherit still has the PMD order set by default, then shmem would still be able to allocate PMD-sized large folios if the global shmem interface is enabled.