Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752647Ab3IJXNL (ORCPT ); Tue, 10 Sep 2013 19:13:11 -0400 Received: from g4t0017.houston.hp.com ([15.201.24.20]:40367 "EHLO g4t0017.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751136Ab3IJXNH (ORCPT ); Tue, 10 Sep 2013 19:13:07 -0400 Message-ID: <522F5275.7050001@hp.com> Date: Tue, 10 Sep 2013 17:10:13 +0000 From: Thavatchai Makphaibulchoke User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130803 Thunderbird/17.0.8 MIME-Version: 1.0 To: "Theodore Ts'o" , Andreas Dilger CC: T Makphaibulchoke , Al Viro , "linux-ext4@vger.kernel.org List" , Linux Kernel Mailing List , "linux-fsdevel@vger.kernel.org Devel" , aswin@hp.com, Linus Torvalds , aswin_proj@lists.hp.com Subject: Re: [PATCH v3 0/2] ext4: increase mbcache scalability References: <1374108934-50550-1-git-send-email-tmac@hp.com> <1378312756-68597-1-git-send-email-tmac@hp.com> <20130905023522.GA21268@thunk.org> <52285395.1070508@hp.com> <0787C579-7E2C-4864-B8F4-98816E1E50A2@dilger.ca> <5229C939.8030108@hp.com> <62D71A85-C7EE-4F5F-B481-5329F0282044@dilger.ca> <20130910210250.GH29237@thunk.org> In-Reply-To: <20130910210250.GH29237@thunk.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1705 Lines: 29 On 09/10/2013 09:02 PM, Theodore Ts'o wrote: > On Tue, Sep 10, 2013 at 02:47:33PM -0600, Andreas Dilger wrote: >> I agree that SELinux is enabled on enterprise distributions by default, >> but I'm also interested to know how much overhead this imposes. I would >> expect that writing large external xattrs for each file would have quite >> a significant performance overhead that should not be ignored. Reducing >> the mbcache overhead is good, but eliminating it entirely is better. > > I was under the impression that using a 256 byte inode (which gives a > bit over 100 bytes worth of xattr space) was plenty for SELinux. If > it turns out that SELinux's use of xattrs have gotten especially > piggy, then we may need to revisit the recommended inode size for > those systems who insist on using SELinux... even if we eliminate the > overhead associated with mbcache, the fact that files are requiring a > separate xattr is going to seriously degrade performance. > > - Ted > Thank you Andreas and Ted for the explanations and comments. Yes, I see both of your points now. Though we may reduce the mbcache overhead, due to the overhead of additional xattr I/O it would be better to provide some data to help users or distros to determine whether they will be better off completely disabling SELinux or increasing the inode size. I will go ahead and run the suggested experiments and get back with the results. Thanks, Mak. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/