Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761688Ab2FHX1F (ORCPT ); Fri, 8 Jun 2012 19:27:05 -0400 Received: from mga03.intel.com ([143.182.124.21]:38513 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759866Ab2FHX07 (ORCPT ); Fri, 8 Jun 2012 19:26:59 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="asc'?scan'208";a="153788116" Date: Sat, 9 Jun 2012 02:28:11 +0300 From: "Kirill A. Shutemov" To: Andrew Morton Cc: Alexander Viro , Linus Torvalds , Boaz Harrosh , Tao Ma , Nick Piggin , "Dmitry V. Levin" , v9fs-developer@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org, linux-btrfs@vger.kernel.org, ceph-devel@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, codalist@TELEMANN.coda.cs.cmu.edu, ecryptfs@vger.kernel.org, osd-dev@open-osd.org, linux-ext4@vger.kernel.org, fuse-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, jfs-discussion@lists.sourceforge.net, logfs@logfs.org, linux-nfs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, ocfs2-devel@oss.oracle.com, reiserfs-devel@vger.kernel.org Subject: Re: [RFC, PATCH, RESEND] fs: push rcu_barrier() from deactivate_locked_super() to filesystems Message-ID: <20120608232811.GA18981@otc-wbsnb-06> References: <1339191663-17693-1-git-send-email-kirill.shutemov@linux.intel.com> <20120608150253.e42464a6.akpm@linux-foundation.org> <20120608221446.GA18250@otc-wbsnb-06> <20120608152550.258d6a30.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="BOKacYhQ+x31HxR3" Content-Disposition: inline In-Reply-To: <20120608152550.258d6a30.akpm@linux-foundation.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4320 Lines: 103 --BOKacYhQ+x31HxR3 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jun 08, 2012 at 03:25:50PM -0700, Andrew Morton wrote: > On Sat, 9 Jun 2012 01:14:46 +0300 > "Kirill A. Shutemov" wrote: >=20 > > On Fri, Jun 08, 2012 at 03:02:53PM -0700, Andrew Morton wrote: > > > On Sat, 9 Jun 2012 00:41:03 +0300 > > > "Kirill A. Shutemov" wrote: > > >=20 > > > > There's no reason to call rcu_barrier() on every deactivate_locked_= super(). > > > > We only need to make sure that all delayed rcu free inodes are flus= hed > > > > before we destroy related cache. > > > >=20 > > > > Removing rcu_barrier() from deactivate_locked_super() affects some > > > > fas paths. E.g. on my machine exit_group() of a last process in IPC > > > > namespace takes 0.07538s. rcu_barrier() takes 0.05188s of that time. > > >=20 > > > What an unpleasant patch. Is final-process-exiting-ipc-namespace a > > > sufficiently high-frequency operation to justify the change? >=20 > This, please. ALT Linux guys use a namespaces (including IPC namespace) to create sandbox[1] for build system and other use cases. The build system calls the sandboxing wrapper frequently on setup building chroot and build prepare. This kind of delays affect timings significantly. [1] http://git.altlinux.org/people/ldv/packages/hasher-priv.git > > > I don't really understand what's going on here. Are you saying that > > > there is some filesystem against which we run deactivate_locked_super= () > > > during exit_group(), and that this filesystem doesn't use rcu-freeing > > > of inodes? The description needs this level of detail, please. >=20 > You still haven't explained where this deactivate_locked_super() call > is coming from. Oh well. Call Trace: [] schedule+0x3a/0x50 [] schedule_timeout+0x1cd/0x2c0 [] ? mqueue_destroy_inode+0x17/0x20 [] wait_for_common+0xc4/0x160 [] ? try_to_wake_up+0x2a0/0x2a0 [] ? call_rcu_sched+0x10/0x20 [] ? call_rcu_bh+0x20/0x20 [] wait_for_completion+0x18/0x20 [] _rcu_barrier.clone.31+0x9b/0xb0 [] rcu_barrier_sched+0x10/0x20 [] rcu_barrier+0x9/0x10 [] deactivate_locked_super+0x49/0x90 [] deactivate_super+0x45/0x60 [] mntput_no_expire+0x104/0x150 [] mntput+0x1c/0x30 [] kern_unmount+0x27/0x30 [] mq_put_mnt+0x10/0x20 [] put_ipc_ns+0x3f/0xb0 [] free_nsproxy+0x3c/0xa0 [] switch_task_namespaces+0x33/0x40 [] exit_task_namespaces+0xb/0x10 [] do_exit+0x4b4/0x8a0 [] do_group_exit+0x53/0xc0 [] sys_exit_group+0x12/0x20 [] system_call_fastpath+0x16/0x1b --=20 Kirill A. Shutemov --BOKacYhQ+x31HxR3 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJP0oqLAAoJEAd+omnVudOMcP4QAKbbNKoSRJWh+GzG3pvNAERZ iqlVtKYEJR+i+ABIR3HFB3QHWuUceas8yvu1UhyX2X4NbM80uJXPsw4DDfokoGSp HMbSkAnax60LiLXy25HIkKKZGz+Ku/moPXrjLt6fKZ0jaH1Fg0WWRSTzvl3StEAs ffFNVb1ij6eRMgedrmP0XKJ1LFeYh4CJLZg26EvYLgY5LwLNGaV6w4PyQsdcN0n7 GPr6PQRYaEasB+QYDCzvHOf/2MdRqel8XdJZBBoEWirPZ89+98/3tRghY2PSoLOc il/URPjcM+ni4BRYAuV5w3iVzR0uDxPZBEnQ+VC5ZGq8qQxR03/+Mk5OXNGf5lhn A7OToIUBnbVazr07xz8k+oJNqr4KRSZuUVNzBv5CmLp9O3NcUJmK0Su5YtjwbqVw bAYUQv5mFA4cUC4tiqodc8Nntare/ClKxT8eMGCgSFfMceLVEQN8rNJtGXgBwYGF bjhIbaaBVYPM6Txp1yHdC62ljOLX8YXVZSXCV6KoTm+chksizM0ggDxyDGGFLy5c leG8JFpidGspSGJ6v9eFLoOm00EAYf/sQtiTOq/FQmBh4F6kQ2wx+M0z64uA5cOm p6qQUXbHty1wQCQ0wdj99pmCAm6lvK2VFfm1WTsoBOc4WtHp5bLVAVbXGDAsSCu+ FPI6ekiivc98Ot0YKE2h =mjfa -----END PGP SIGNATURE----- --BOKacYhQ+x31HxR3-- -- 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/