From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-97.freemail.mail.aliyun.com (out30-97.freemail.mail.aliyun.com [115.124.30.97]) (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 CF2DB1BD9D0 for ; Thu, 16 Apr 2026 01:22:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.97 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776302567; cv=none; b=Iu2FEhErCY6BQT6ZiTz++bRc/DEgb1URJYO7dB39gIhiqnX1LKkNgAdKnQO6XMBHyAWTgYzyWYnHb1VgMRwqgQKItoGdVBNTNWnT1arcG9mQBECAp1Oo5XPO3Su5b86/bApCX7+GBd5w/hgMmbjadpijHjj9soLUHtqs5ay6hQk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776302567; c=relaxed/simple; bh=R9yc9AEuiJOGgjeRqp49BQ5XTBY1TaSIkp/P36t+W3c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=MLjXRP1bzX4A9UKOpCZXs4GqnNHMIKSAS2Jm2vJocGbO+1g59BY+N4VdqNMhvI14lHjsid6rAo0CAH6MbtxzQEVXCxqZ0TftjwWkrSPcxudCWjqUvHc2b9VTVxe9rUeVLiUwILFn6u92b/C4LG8O/NwK2YMdn8Tpsl2v/2gz0FQ= 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=EWG5oybv; arc=none smtp.client-ip=115.124.30.97 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="EWG5oybv" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1776302562; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=M0bEAAbgBNmbxicu2CtQb8Q27gLpg83fQgDiS0p6Nz4=; b=EWG5oybvxIkX9t8vcE78+GmHJsxURoAXQb3IXDWC1aITG6x5nAwZHUKVoFZtGJNtnt30/vsAlF3XEsSlIxAA8/0ck/oAzdMWW8+QF4el8teSQUQUoQgJoDys+e7AvSx3gbDuCEsJ4pInr9WQ5qN9d8cinEQCZ97kVwqV2QSht0E= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R141e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033045133197;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0X16GTzA_1776302561; Received: from 30.74.144.131(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0X16GTzA_1776302561 cluster:ay36) by smtp.aliyun-inc.com; Thu, 16 Apr 2026 09:22:41 +0800 Message-ID: <16745f2b-b008-4df1-ac76-f18b4a826dbd@linux.alibaba.com> Date: Thu, 16 Apr 2026 09:22:40 +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] mm: shmem: don't set large-order range for internal shmem mount To: Zi Yan Cc: "David Hildenbrand (Arm)" , akpm@linux-foundation.org, hughd@google.com, willy@infradead.org, ljs@kernel.org, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <2d138a3f-0006-4a01-852a-4570d7ba781d@linux.alibaba.com> <1a3cb6b2-94e0-4268-8cd9-1f9a9deb6c6b@linux.alibaba.com> <875dc63b-0cd2-49e5-8b0d-3fb062789813@kernel.org> <846B17B0-1BAF-4959-8FC2-42744C44B1D6@nvidia.com> From: Baolin Wang In-Reply-To: <846B17B0-1BAF-4959-8FC2-42744C44B1D6@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 4/16/26 9:11 AM, Zi Yan wrote: > On 15 Apr 2026, at 21:05, Baolin Wang wrote: > >> On 4/15/26 10:36 PM, David Hildenbrand (Arm) wrote: >>> On 4/15/26 12:05, Baolin Wang wrote: >>>> >>>> >>>> On 4/15/26 5:54 PM, David Hildenbrand (Arm) wrote: >>>>>> >>>>>> Yes, that makes sense. >>>>>> >>>>>> However, it’s also possible that the mapping does not support large >>>>>> folios, yet anonymous shmem can still allocate large folios via the >>>>>> sysfs interfaces. That doesn't make sense, right? >>>>> >>>>> That's what I am saying: if there could be large folios in there, then >>>>> let's tell the world. >>>>> >>>>> Getting in a scenario where the mapping claims to not support large >>>>> folios, but then we have large folios in there is inconsistent, not? >>>>> >>>>> [...] >>>>> >>>>>> >>>>>> For the current anonymous shmem (tmpfs is already clear, no questions), >>>>>> I don’t think there will be any "will never have/does never allow" >>>>>> cases, because it can be changed dynamically via the sysfs interfaces. >>>>> >>>>> Right. It's about non-anon shmem with huge=off. >>>>> >>>>>> >>>>>> If we still want that logic, then for anonymous shmem we can treat it as >>>>>> always "might have large folios". >>>> >>>> OK. To resolve the confusion about 1, the logic should be changed as >>>> follows. Does that make sense to you? >>>> >>>> if (sbinfo->huge || (sb->s_flags & SB_KERNMOUNT)) >>>>     mapping_set_large_folios(inode->i_mapping); >>> >>> I think that's better. >> >> Thanks for your valuable input. >> >> But has Willy says, maybe we can just >>> unconditionally set it and have it even simpler. >> >> However, for tmpfs mounts, we should still respect the 'huge=' mount option. See commit 5a90c155defa ("tmpfs: don't enable large folios if not supported"). > > Is it possible to get sbinfo->huge during tmpfs’s folio allocation time, so that > even if all tmpfs has mapping_set_large_folios() but sbinfo->huge can still > decide whether huge page will be allocated for a tmpfs? Yes, of course. However, the issue isn’t whether tmpfs allows allocating large folios. The problem commit 5a90c155defa tries to fix is that when tmpfs is mounted with the 'huge=never' option, we will not allocate large folios for it. Then when writing tmpfs files, generic_perform_write() will call mapping_max_folio_size() to get the chunk size and ends up with an order-9 size for writing tmpfs files. However, this tmpfs file is populated only with small folios, resulting in a performance regression.