Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753466AbYK1SDJ (ORCPT ); Fri, 28 Nov 2008 13:03:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752487AbYK1SCv (ORCPT ); Fri, 28 Nov 2008 13:02:51 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:36213 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752295AbYK1SCt (ORCPT ); Fri, 28 Nov 2008 13:02:49 -0500 Date: Fri, 28 Nov 2008 19:02:20 +0100 From: Ingo Molnar To: Al Viro Cc: Eric Dumazet , David Miller , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, kernel-testers@vger.kernel.org, Mike Galbraith , Peter Zijlstra , Linux Netdev List , Christoph Lameter , Christoph Hellwig , rth@twiddle.net, ink@jurassic.park.msu.ru Subject: Re: [PATCH 6/6] fs: Introduce kern_mount_special() to mount special vfs Message-ID: <20081128180220.GK10487@elte.hu> References: <20081121083044.GL16242@elte.hu> <49267694.1030506@cosmosbay.com> <20081121.010508.40225532.davem@davemloft.net> <4926AEDB.10007@cosmosbay.com> <4926D022.5060008@cosmosbay.com> <20081121152148.GA20388@elte.hu> <4926D39D.9050603@cosmosbay.com> <20081121153453.GA23713@elte.hu> <492DDCAB.1070204@cosmosbay.com> <20081128092604.GL28946@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081128092604.GL28946@ZenIV.linux.org.uk> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6326 Lines: 154 * Al Viro wrote: > On Thu, Nov 27, 2008 at 12:32:59AM +0100, Eric Dumazet wrote: > > This function arms a flag (MNT_SPECIAL) on the vfs, to avoid > > refcounting on permanent system vfs. > > Use this function for sockets, pipes, anonymous fds. > > IMO that's pushing it past the point of usefulness; unless you can show > that this really gives considerable win on pipes et.al. *AND* that it > doesn't hurt other loads... The numbers look pretty convincing: > > (socket8 bench result : from 2.94s to 2.23s) And i wouldnt expect it to hurt real-filesystem workloads. Here's the contemporary trace of a typical ext3- sys_open(): 0) | sys_open() { 0) | do_sys_open() { 0) | getname() { 0) 0.367 us | kmem_cache_alloc(); 0) | strncpy_from_user(); { 0) | _cond_resched() { 0) | need_resched() { 0) 0.363 us | constant_test_bit(); 0) 1. 47 us | } 0) 1.815 us | } 0) 2.587 us | } 0) 4. 22 us | } 0) | alloc_fd() { 0) 0.480 us | _spin_lock(); 0) 0.487 us | expand_files(); 0) 2.356 us | } 0) | do_filp_open() { 0) | path_lookup_open() { 0) | get_empty_filp() { 0) 0.439 us | kmem_cache_alloc(); 0) | security_file_alloc() { 0) 0.316 us | cap_file_alloc_security(); 0) 1. 87 us | } 0) 3.189 us | } 0) | do_path_lookup() { 0) 0.366 us | _read_lock(); 0) | path_walk() { 0) | __link_path_walk() { 0) | inode_permission() { 0) | ext3_permission() { 0) 0.441 us | generic_permission(); 0) 1.247 us | } 0) | security_inode_permission() { 0) 0.411 us | cap_inode_permission(); 0) 1.186 us | } 0) 3.555 us | } 0) | do_lookup() { 0) | __d_lookup() { 0) 0.486 us | _spin_lock(); 0) 1.369 us | } 0) 0.442 us | __follow_mount(); 0) 3. 14 us | } 0) | path_to_nameidata() { 0) 0.476 us | dput(); 0) 1.235 us | } 0) | inode_permission() { 0) | ext3_permission() { 0) | generic_permission() { 0) | in_group_p() { 0) 0.410 us | groups_search(); 0) 1.172 us | } 0) 1.994 us | } 0) 2.789 us | } 0) | security_inode_permission() { 0) 0.454 us | cap_inode_permission(); 0) 1.238 us | } 0) 5.262 us | } 0) | do_lookup() { 0) | __d_lookup() { 0) 0.480 us | _spin_lock(); 0) 1.621 us | } 0) 0.456 us | __follow_mount(); 0) 3.215 us | } 0) | path_to_nameidata() { 0) 0.420 us | dput(); 0) 1.193 us | } 0) + 23.551 us | } 0) | path_put() { 0) 0.420 us | dput(); 0) | mntput() { 0) 0.359 us | mntput_no_expire(); 0) 1. 50 us | } 0) 2.544 us | } 0) + 27.253 us | } 0) + 28.850 us | } 0) + 33.217 us | } 0) | may_open() { 0) | inode_permission() { 0) | ext3_permission() { 0) 0.480 us | generic_permission(); 0) 1.229 us | } 0) | security_inode_permission() { 0) 0.405 us | cap_inode_permission(); 0) 1.196 us | } 0) 3.589 us | } 0) 4.600 us | } 0) | nameidata_to_filp() { 0) | __dentry_open() { 0) | file_move() { 0) 0.470 us | _spin_lock(); 0) 1.243 us | } 0) | security_dentry_open() { 0) 0.344 us | cap_dentry_open(); 0) 1.139 us | } 0) 0.412 us | generic_file_open(); 0) 0.561 us | file_ra_state_init(); 0) 5.714 us | } 0) 6.483 us | } 0) + 46.494 us | } 0) 0.453 us | inotify_dentry_parent_queue_event(); 0) 0.403 us | inotify_inode_queue_event(); 0) | fd_install() { 0) 0.440 us | _spin_lock(); 0) 1.247 us | } 0) | putname() { 0) | kmem_cache_free() { 0) | virt_to_head_page() { 0) 0.369 us | constant_test_bit(); 0) 1. 23 us | } 0) 1.738 us | } 0) 2.422 us | } 0) + 60.560 us | } 0) + 61.368 us | } and here's a sys_close(): 0) | sys_close() { 0) 0.540 us | _spin_lock(); 0) | filp_close() { 0) 0.437 us | dnotify_flush(); 0) 0.401 us | locks_remove_posix(); 0) 0.349 us | fput(); 0) 2.679 us | } 0) 4.452 us | } i'd be surprised to see a flag to show up in that codepath. Eric, does your testing confirm that? Ingo -- 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/