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 214BA205AD6 for ; Tue, 12 Nov 2024 03:20:00 +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=1731381603; cv=none; b=D5rmLzfWdkw7VREZuBVHPcY3PYJJjyXwqCVHmsduQpFzEiBoDe/rEj2B0r9y5v/nqcNT5DiNCFrrJi+jJ9ZRI/6/DkhWtapkYfnBgIMKEA+DT6HnOXqK7J1LS5j00DX203Y+duHsMkmYddxMvurm4gTgokgmxSL6BOXmP6/2WO0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731381603; c=relaxed/simple; bh=H5MhTUzaqEvc7R5sYo+bar5EY0cg4c7zl0PllNDdkpw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=bjf+ZxtQs61947APmasMqDv7LJcHtFuj5vA3qoUscnCh4cSomIAHEqJrfTIHjxxVXRbvfyjrXS+LxVMcjo1l2+U7dCSDYK4eE64xkfVOAg0gM6wfAFpIULg7GupmznNXeZpxcktt8lttJEaG7FzJ4gZtlPhvd3MPFB8NgGQNsLE= 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=q2E4YcB6; 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="q2E4YcB6" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1731381593; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=vAs1rV77DkI2iKDI266dN+In2P7tHRg+caJMvkuicwo=; b=q2E4YcB6AFPKouqq5MU4YBdfnl+C1YwFciMChKeabH3YbejT0QaawoIiCGUZltU67GvLZX6x0PDUVWunqGGLbSbO+KUYod7FMgfwpGB4B75PXBmM7giJ8cILhIx4mVrisYHJJO9F8llFuZ3+CDr0bhyA8E1ut4ivzGjYVg1hNHA= Received: from 30.74.144.120(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WJFQ5jo_1731381590 cluster:ay36) by smtp.aliyun-inc.com; Tue, 12 Nov 2024 11:19:51 +0800 Message-ID: <87df7d30-6ef1-49d4-9a94-ce78e0ffc5af@linux.alibaba.com> Date: Tue, 12 Nov 2024 11:19:49 +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 0/4] Support large folios for tmpfs To: David Hildenbrand , akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, wangkefeng.wang@huawei.com, 21cnbao@gmail.com, ryan.roberts@arm.com, ioworker0@gmail.com, da.gomez@samsung.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <3d49fbf8-866f-485b-b7fa-a89bbfb3cd7c@redhat.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2024/11/12 03:47, David Hildenbrand wrote: > On 09.11.24 08:12, Baolin Wang wrote: >> >> >> On 2024/11/8 23:30, David Hildenbrand wrote: >>> On 08.11.24 05:12, Baolin Wang wrote: >>>> Traditionally, tmpfs only supported PMD-sized huge folios. However >>>> nowadays >>>> with other file systems supporting any sized large folios, and >>>> extending >>>> anonymous to support mTHP, we should not restrict tmpfs to allocating >>>> only >>>> PMD-sized huge folios, making it more special. Instead, we should allow >>>> tmpfs can allocate any sized large folios. >>>> >>>> Considering that tmpfs already has the 'huge=' option to control the >>>> huge >>>> folios allocation, we can extend the 'huge=' option to allow any sized >>>> huge >>>> folios. The semantics of the 'huge=' mount option are: >>>> >>>> huge=never: no any sized huge folios >>>> huge=always: any sized huge folios >>>> huge=within_size: like 'always' but respect the i_size >>>> huge=advise: like 'always' if requested with fadvise()/madvise() >>>> >>>> Note: for tmpfs mmap() faults, due to the lack of a write size hint, >>>> still >>>> allocate the PMD-sized huge folios if huge=always/within_size/advise >>>> is set. >>> >>> So, no fallback to smaller sizes for now in case we fail to allocate a >>> PMD one? Of course, this can be added later fairly easily. >> >> Right. I have no strong preference on this. If no one objects, I can add >> a fallback to smaller large folios if the PMD sized allocation fails in >> the next version. > > I'm fine with a staged approach, to perform this change separately. Sure. >>>> Moreover, the 'deny' and 'force' testing options controlled by >>>> '/sys/kernel/mm/transparent_hugepage/shmem_enabled', still retain the >>>> same >>>> semantics. The 'deny' can disable any sized large folios for tmpfs, >>>> while >>>> the 'force' can enable PMD sized large folios for tmpfs. >>>> >>>> Any comments and suggestions are appreciated. Thanks. >>>> >>>> Hi David, >>>> I did not add a new Kconfig option to control the default behavior of >>>> 'huge=' >>>> in the current version. I have not changed the default behavior at this >>>> time, and let's see if there is a need for this. >>> >>> Likely we want to change the default at some point so people might get a >>> benefit in more scenarios automatically. But I did not investigate how >>> /tmp is mapped as default by Fedora, for example. >> >> Personally, adding a cmdline to change the default value might be more >> useful than the Kconfig. Anyway, I still want to investigate if there is >> a real need. > > Likely both will be reasonable to have. > > FWIW, "systemctl cat tmp.mount" on a Fedora40 system tells me > "Options=mode=1777,strictatime,nosuid,nodev,size=50%%,nr_inodes=1m" > > To be precise: > > $ grep tmpfs /etc/mtab > vendorfw /usr/lib/firmware/vendor tmpfs rw,relatime,mode=755,inode64 0 0 > devtmpfs /dev devtmpfs > rw,nosuid,size=4096k,nr_inodes=4063361,mode=755,inode64 0 0 > tmpfs /dev/shm tmpfs rw,nosuid,nodev,inode64 0 0 > tmpfs /run tmpfs > rw,nosuid,nodev,size=6511156k,nr_inodes=819200,mode=755,inode64 0 0 > tmpfs /tmp tmpfs > rw,nosuid,nodev,size=16277892k,nr_inodes=1048576,inode64 0 0 > tmpfs /run/user/100813 tmpfs > rw,nosuid,nodev,relatime,size=3255576k,nr_inodes=813894,mode=700,uid=100813,gid=100813,inode64 0 0 > > > Having a way to change the default will likely be extremely helpful. Thanks. I'd like to add a command line option like 'transparent_hugepage_shmem' to control the default value.