Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752020AbYJCEoc (ORCPT ); Fri, 3 Oct 2008 00:44:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753270AbYJCEoP (ORCPT ); Fri, 3 Oct 2008 00:44:15 -0400 Received: from casper.infradead.org ([85.118.1.10]:38256 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752960AbYJCEoO (ORCPT ); Fri, 3 Oct 2008 00:44:14 -0400 Date: Thu, 2 Oct 2008 21:43:53 -0700 From: Arjan van de Ven To: Andrew Morton Cc: Jens Axboe , linux-kernel@vger.kernel.org, Alan Cox Subject: Re: [PATCH] Give kjournald a IOPRIO_CLASS_RT io priority Message-ID: <20081002214353.30873f98@infradead.org> In-Reply-To: <20081002214000.89420bb3.akpm@linux-foundation.org> References: <20081001200034.65eb67d6@infradead.org> <20081001215638.3a65134c.akpm@linux-foundation.org> <20081002062736.GR19428@kernel.dk> <20081001235501.2b7f50fe.akpm@linux-foundation.org> <20081002061236.3c71c877@infradead.org> <20081002132457.46ad8d05.akpm@linux-foundation.org> <20081002210117.0f5062f7@infradead.org> <20081002212355.621a4fb6@infradead.org> <20081002214000.89420bb3.akpm@linux-foundation.org> Organization: Intel X-Mailer: Claws Mail 3.5.0 (GTK+ 2.12.12; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2350 Lines: 44 > [ 517.067572] [] warn_on_slowpath+0x41/0x65 > [ 517.067652] [] io_schedule+0x77/0xb0 > [ 517.067659] [] sync_buffer+0x33/0x37 > [ 517.067666] [] __wait_on_bit_lock+0x34/0x5e > [ 517.067682] [] out_of_line_wait_on_bit_lock+0xab/0xb3 > [ 517.067707] [] __lock_buffer+0x24/0x2a > [ 517.067715] [] do_get_write_access+0x64/0x3b1 > [ 517.067743] [] journal_get_write_access+0x1b/0x2a > [ 517.067752] [] __ext3_journal_get_write_access+0x19/0x3c > [ 517.067761] [] ext3_reserve_inode_write+0x34/0x68 > [ 517.067769] [] ext3_mark_inode_dirty+0x2f/0x46 > [ 517.067777] [] ext3_dirty_inode+0x53/0x67 > [ 517.067784] [] __mark_inode_dirty+0x29/0x144 > [ 517.067794] [] file_update_time+0x80/0xa9 > [ 517.067803] [] __generic_file_aio_write_nolock+0x2f0/0x41b > [ 517.067842] [] generic_file_aio_write+0x5a/0xb7 > [ 517.067850] [] ext3_file_write+0x1a/0x89 > [ 517.067858] [] do_sync_write+0xab/0xe9 > [ 517.067896] [] vfs_write+0x8a/0x12e > [ 517.067903] [] sys_write+0x3b/0x60 > [ 517.067910] [] sysenter_do_call+0x12/0x2f > [ 517.067919] ======================= > [ 517.067923] ---[ end trace de523043f88bd9a7 ]--- > That's the one - the lock_buffer() in do_get_write_access(). It's a > major contention site and it'd be a major win if we could fix it. > Even if we resorted to some nasty thing like taking a temp copy of the > buffer's contents. I also notice it's part of "file_update_time". Do we really need to go all the way down to this level of synchronicity for that? (I also randomly wonder if we, in the write path, dirty the inode twice, once for size once for item, and if we then also reserve two slots in the journal for that..... but I'm showing my total ignorance of JBD internals here) -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- 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/