From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-118.freemail.mail.aliyun.com (out30-118.freemail.mail.aliyun.com [115.124.30.118]) (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 698CB3B192 for ; Sat, 9 Nov 2024 07:12:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.118 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731136355; cv=none; b=kmIi2uDDv2/NK+OF7wb62LHhrXOZhX26bqCbPUR9q4b3k8Z3lTRYebjPc79zEdr9sGoo93VQGAgfjEq6jp7cCIFoWYGd16IhOgCk8YZY115WRHON/VmKFQKDoyVCj81Ruig3FRfHzAESuJSwUbxy9r3Inef7Ap/fnOMGrK7FpGY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731136355; c=relaxed/simple; bh=Vox/FHuQsiAnvbmzX5WEbHKtviQOqFrkUmXLLSWLFZk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=H8F2WS84Hpvtcer2KI+rL2p6FLYG2J2yr16upvSUrZjAxDVLnnB4xsbqymBNOhYXbgoKo+duIRftNwKTeiHid5Iy431qk3+Mjnv/gaFBzYD1v21cWwKTJ3J58/UDbz49GdyGbMTtpnU1am3Wtp96OPlgAIBLAIektmRenL6E6U0= 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=VbpfmhGH; arc=none smtp.client-ip=115.124.30.118 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="VbpfmhGH" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1731136344; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=A6UqBYVCS/TOTFjQt3Tzhr5BGkUP2D8w/Z3WsnhNXlI=; b=VbpfmhGH/b/LoahYw/of4FTD7LfDHwVB6j73EFwjcxgVUmUMirrH3SHomYjtHrReiQ52DqZSGvO1W4IWpDAneDQrU3h/yFg6MKASLRVitDsPnkmotdnIm9z4Eq3bXraiZ4K92UTADs290N4BFzXOCQEP8kRFXugL96v8O6a9BJo= Received: from 30.15.226.209(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WJ.rpS._1731136341 cluster:ay36) by smtp.aliyun-inc.com; Sat, 09 Nov 2024 15:12:23 +0800 Message-ID: Date: Sat, 9 Nov 2024 15:12:21 +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: <3d49fbf8-866f-485b-b7fa-a89bbfb3cd7c@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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. >> 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.