From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 411B535AC3B for ; Fri, 2 Oct 2026 19:24:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790969046; cv=none; b=NsIyoJyrN9f4MWY9rqBemYP3HYNJi5F/jbFZy1ufEDNwF4xFqFjDW4PXSp838FPR+XON6R/28qQJ7dwYkbbCvcBDwcSjS4t5D0LIXqt76lF727bD+aQ3bFzbqgJqFZHYnJyH8dB3TEhI9W5Cron0RmWDsfM85mS1txbd5xrD93U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790969046; c=relaxed/simple; bh=auZJr2SkeRn8HhZlmY+Gcgh7DZ9Dy87FyOPOIlDak4c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=SryfX8cnPxx0NXDaDEOWjKlR47C28Av9Nft4uicfzO4Gj+3nP2bonIuQVWC8tYvsBJABACmhyPywwNR7vbJgGRfiVxAhpc5gZkA5n1iyhMFXZxMj5GhxXv29H1qk8WmnX+wZ84Jjs11+8m1cM7mBu9klHK+AG4j1xzzeWEu0hk8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BGSX/Kbt; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BGSX/Kbt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 339B21F000FF; Fri, 2 Oct 2026 19:23:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790969044; bh=o3DcXBfUguoi60aMXCNeicGNJ5nj03dbbSlS/dsM2Sk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=BGSX/Kbts2HyomUYIll1ZSW1Dc6xBceYErF3oCIvBLGsnn+9W/iL8dUWzD10Xxshv ZN83CvovSLCevLrxWllAASgTHRUTKqmEDI8r3B61oraf+GBHIM9rlNJra3/KUEcZwc Gj3mYj5JVSkng+Z1vgJR2AZoiHbPmGwRvgg3WWugxxYNsWyLXNycxtqZyemtlKslJv Xr3zyVh84R34zkPGPo3zG7qHoDMJZ6WRceBLfPeQHeWmJJ2QYxjRNGKEp5Z65cWpBM UoaqMSQstAgxR6XPvPEi1TRTfgUaDiaxDCVp7Kq3iHcgWMIx1HNSyd6TRyX8eGGm+w vWH/q2umXu0wQ== Message-ID: Date: Fri, 2 Oct 2026 21:23:54 +0200 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 07/14] mm: shmem: allow THP support determination at folio allocation time To: Luiz Capitulino , linux-kernel@vger.kernel.org, linux-mm@kvack.org, baolin.wang@linux.alibaba.com, 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, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, hughd@google.com, dave.hansen@linux.intel.com, djbw@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, akpm@linux-foundation.org, yintirui@huawei.com, dev.jain@arm.com, usama.arif@linux.dev References: From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/18/26 03:45, Luiz Capitulino wrote: > In order to enable THP support in shmem today, besides the user > configuration required, the CPU must support PMD-sized pages. This > is the case because of the following has_transparent_hugepage() > usage: > > - shmem_parse_one() and shmem_parse_huge(): Check if THP is built-in and > if the CPU supports PMD-sized pages > > - shmem_init(): Since the CONFIG_TRANSPARENT_HUGEPAGE guard is outside > the code block calling has_transparent_hugepage(), the > has_transparent_hugepage() call is exclusively checking if the CPU > supports PMD-sized pages > > While it's necessary to check if CONFIG_TRANSPARENT_HUGEPAGE is enabled > in all cases, shmem can determine THP size support at folio allocation > time. Therefore, drop the has_transparent_hugepage() usage listed above > while keeping the CONFIG_TRANSPARENT_HUGEPAGE checks. > > Additionally, we need to check if PMD size order is supported in > shmem_getattr(). Use pgtable_has_pmd_leaves() for that. > > Reviewed-by: Baolin Wang > Signed-off-by: Luiz Capitulino > --- > mm/shmem.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 776dff8a848e..930657d05375 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -690,7 +690,7 @@ static int shmem_parse_huge(const char *str) > else > return -EINVAL; > > - if (!has_transparent_hugepage() && > + if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && > huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY) > return -EINVAL; > > @@ -1524,6 +1524,8 @@ static int shmem_getattr(struct mnt_idmap *idmap, > generic_fillattr(idmap, request_mask, inode, stat); > > orders = shmem_huge_global_enabled(inode, 0, 0, false, NULL, 0); I'm curious: why is that not handled inside shmem_huge_global_enabled() ? If PMD order is impossible (well, okay, it is possible, but we simply cannot map these things through PMDs), I would expect that we never list them as "enabled". (while shmem could allocate PMD folios, it would have to map them always through PTEs. I think this would be possible through some changes, but we can defer that to some future work). -- Cheers, David