From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753750AbdJHTv1 (ORCPT ); Sun, 8 Oct 2017 15:51:27 -0400 Received: from out0-200.mail.aliyun.com ([140.205.0.200]:52765 "EHLO out0-200.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753651AbdJHTv0 (ORCPT ); Sun, 8 Oct 2017 15:51:26 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R251e4;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e02c03302;MF=yang.s@alibaba-inc.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---.94I4Cx0_1507492273; Subject: Re: [RFC PATCH] mm: shm: round up tmpfs size to huge page size when huge=always To: "Kirill A. Shutemov" Cc: kirill.shutemov@linux.intel.com, hughd@google.com, mhocko@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1507321330-22525-1-git-send-email-yang.s@alibaba-inc.com> <20171008125651.3mxiayuvuqi2hiku@node.shutemov.name> From: "Yang Shi" Message-ID: <9357e3f2-6e49-b47a-20a6-ec7791c28fbd@alibaba-inc.com> Date: Mon, 09 Oct 2017 03:51:06 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20171008125651.3mxiayuvuqi2hiku@node.shutemov.name> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/8/17 5:56 AM, Kirill A. Shutemov wrote: > On Sat, Oct 07, 2017 at 04:22:10AM +0800, Yang Shi wrote: >> When passing "huge=always" option for mounting tmpfs, THP is supposed to >> be allocated all the time when it can fit, but when the available space is >> smaller than the size of THP (2MB on x86), shmem fault handler still tries >> to allocate huge page every time, then fallback to regular 4K page >> allocation, i.e.: >> >> # mount -t tmpfs -o huge,size=3000k tmpfs /tmp >> # dd if=/dev/zero of=/tmp/test bs=1k count=2048 >> # dd if=/dev/zero of=/tmp/test1 bs=1k count=2048 >> >> The last dd command will handle 952 times page fault handler, then exit >> with -ENOSPC. >> >> Rounding up tmpfs size to THP size in order to use THP with "always" >> more efficiently. And, it will not wast too much memory (just allocate >> 511 extra pages in worst case). > > Hm. I don't think it's good idea to silently increase size of fs. How about printing a warning to say the filesystem is resized? > > Maybe better just refuse to mount with huge=always for too small fs? It sounds fine too. When mounting tmpfs with "huge=always", if the size is not THP size aligned, it just can refuse to mount, then show warning about alignment restriction. Thanks, Yang >