From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753798Ab1EEM1x (ORCPT ); Thu, 5 May 2011 08:27:53 -0400 Received: from mga09.intel.com ([134.134.136.24]:41974 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753170Ab1EEM1w (ORCPT ); Thu, 5 May 2011 08:27:52 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.64,319,1301900400"; d="scan'208";a="638441823" Date: Thu, 5 May 2011 20:27:32 +0800 From: Wu Fengguang To: Jan Kara Cc: Andrew Morton , Dave Chinner , Christoph Hellwig , LKML , "linux-fsdevel@vger.kernel.org" Subject: Re: [PATCH 3/3] writeback: avoid extra sync work at enqueue time Message-ID: <20110505122732.GC1294@localhost> References: <20110502031750.135798606@intel.com> <20110502033035.789279347@intel.com> <20110504212427.GI6968@quack.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110504212427.GI6968@quack.suse.cz> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 05, 2011 at 05:24:27AM +0800, Jan Kara wrote: > On Mon 02-05-11 11:17:53, Wu Fengguang wrote: > > This removes writeback_control.wb_start and does more straightforward > > sync livelock prevention by setting .older_than_this to prevent extra > > inodes from being enqueued in the first place. > > > > --- linux-next.orig/fs/fs-writeback.c 2011-05-02 11:17:24.000000000 +0800 > > +++ linux-next/fs/fs-writeback.c 2011-05-02 11:17:27.000000000 +0800 > > @@ -683,10 +672,12 @@ static long wb_writeback(struct bdi_writ > > * (quickly) tag currently dirty pages > > * (maybe slowly) sync all tagged pages > > */ > > - if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_sync) > > + if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_sync) { > > write_chunk = LONG_MAX; > > + oldest_jif = jiffies; > > + wbc.older_than_this = &oldest_jif; > > + } > What are the implications of not doing dirty-time livelock avoidance for > other types of writeback? Is that a mistake? I'd prefer to have in > wb_writeback(): > if (wbc.for_kupdate) > oldest_jif = jiffies - msecs_to_jiffies(dirty_expire_interval * 10); > else > oldest_jif = jiffies; > wbc.older_than_this = &oldest_jif; > > And when you have this, you can make wbc.older_than_this just a plain > number and remove all those checks for wbc.older_than_this == NULL. Good point. Here is the fixed patch. Will you send the patch to change the type when the current patches are settled down? Thanks, Fengguang --- Subject: writeback: avoid extra sync work at enqueue time Date: Sat Apr 23 11:26:07 CST 2011 This removes writeback_control.wb_start and does more straightforward sync livelock prevention by setting .older_than_this to prevent extra inodes from being enqueued in the first place. CC: Jan Kara Signed-off-by: Wu Fengguang --- fs/fs-writeback.c | 16 +++------------- include/linux/writeback.h | 3 --- 2 files changed, 3 insertions(+), 16 deletions(-) --- linux-next.orig/fs/fs-writeback.c 2011-05-04 20:19:20.000000000 +0800 +++ linux-next/fs/fs-writeback.c 2011-05-05 13:15:42.000000000 +0800 @@ -544,15 +544,6 @@ static int writeback_sb_inodes(struct su continue; } - /* - * Was this inode dirtied after sync_sb_inodes was called? - * This keeps sync from extra jobs and livelock. - */ - if (inode_dirtied_after(inode, wbc->wb_start)) { - spin_unlock(&inode->i_lock); - return 1; - } - __iget(inode); pages_skipped = wbc->pages_skipped; @@ -585,9 +576,6 @@ static void __writeback_inodes_wb(struct { int ret = 0; - if (!wbc->wb_start) - wbc->wb_start = jiffies; /* livelock avoidance */ - while (!list_empty(&wb->b_io)) { struct inode *inode = wb_inode(wb->b_io.prev); struct super_block *sb = inode->i_sb; @@ -686,7 +674,9 @@ static long wb_writeback(struct bdi_writ if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_sync) write_chunk = LONG_MAX; - wbc.wb_start = jiffies; /* livelock avoidance */ + oldest_jif = jiffies; + wbc.older_than_this = &oldest_jif; + for (;;) { /* * Stop writeback when nr_pages has been consumed --- linux-next.orig/include/linux/writeback.h 2011-05-04 20:19:20.000000000 +0800 +++ linux-next/include/linux/writeback.h 2011-05-05 13:14:53.000000000 +0800 @@ -26,9 +26,6 @@ struct writeback_control { enum writeback_sync_modes sync_mode; unsigned long *older_than_this; /* If !NULL, only write back inodes older than this */ - unsigned long wb_start; /* Time writeback_inodes_wb was - called. This is needed to avoid - extra jobs and livelock */ long nr_to_write; /* Write this many pages, and decrement this for each page written */ long pages_skipped; /* Pages which were not written */