From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753438AbdJHM4z (ORCPT ); Sun, 8 Oct 2017 08:56:55 -0400 Received: from mail-wm0-f45.google.com ([74.125.82.45]:47454 "EHLO mail-wm0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751027AbdJHM4y (ORCPT ); Sun, 8 Oct 2017 08:56:54 -0400 X-Google-Smtp-Source: AOwi7QBx2UAu4M2E9KaCG2yZHCDO37NImjrWa1ywCK0uHm5f29vVGXPdqAYrMb+hbjI4cPBPmIRxhw== Date: Sun, 8 Oct 2017 15:56:51 +0300 From: "Kirill A. Shutemov" To: Yang Shi 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 Subject: Re: [RFC PATCH] mm: shm: round up tmpfs size to huge page size when huge=always Message-ID: <20171008125651.3mxiayuvuqi2hiku@node.shutemov.name> References: <1507321330-22525-1-git-send-email-yang.s@alibaba-inc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1507321330-22525-1-git-send-email-yang.s@alibaba-inc.com> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Maybe better just refuse to mount with huge=always for too small fs? -- Kirill A. Shutemov