From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760054AbcJROUR (ORCPT ); Tue, 18 Oct 2016 10:20:17 -0400 Received: from mail-lf0-f65.google.com ([209.85.215.65]:36752 "EHLO mail-lf0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757054AbcJROUL (ORCPT ); Tue, 18 Oct 2016 10:20:11 -0400 Date: Tue, 18 Oct 2016 16:20:07 +0200 From: Michal Hocko To: "Kirill A. Shutemov" Cc: "Kirill A. Shutemov" , Hugh Dickins , Andrea Arcangeli , Andrew Morton , Andi Kleen , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] shmem: avoid huge pages for small files Message-ID: <20161018142007.GL12092@dhcp22.suse.cz> References: <20161017121809.189039-1-kirill.shutemov@linux.intel.com> <20161017123021.rlyz44dsf4l4xnve@black.fi.intel.com> <20161017141245.GC27459@dhcp22.suse.cz> <20161017145539.GA26930@node.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161017145539.GA26930@node.shutemov.name> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 17-10-16 17:55:40, Kirill A. Shutemov wrote: > On Mon, Oct 17, 2016 at 04:12:46PM +0200, Michal Hocko wrote: > > On Mon 17-10-16 15:30:21, Kirill A. Shutemov wrote: [...] > > > We add two handle to specify minimal file size for huge pages: > > > > > > - mount option 'huge_min_size'; > > > > > > - sysfs file /sys/kernel/mm/transparent_hugepage/shmem_min_size for > > > in-kernel tmpfs mountpoint; > > > > Could you explain who might like to change the minimum value (other than > > disable the feautre for the mount point) and for what reason? > > Depending on how well CPU microarchitecture deals with huge pages, you > might need to set it higher in order to balance out overhead with benefit > of huge pages. I am not sure this is a good argument. How do a user know and what will help to make that decision? Why we cannot autotune that? In other words, adding new knobs just in case turned out to be a bad idea in the past. > In other case, if it's known in advance that specific mount would be > populated with large files, you might want to set it to zero to get huge > pages allocated from the beginning. Cannot we use [mf]advise for that purpose? -- Michal Hocko SUSE Labs