Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753850AbZIWB1P (ORCPT ); Tue, 22 Sep 2009 21:27:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753786AbZIWB1P (ORCPT ); Tue, 22 Sep 2009 21:27:15 -0400 Received: from mga14.intel.com ([143.182.124.37]:26689 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753784AbZIWB1O (ORCPT ); Tue, 22 Sep 2009 21:27:14 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.44,434,1249282800"; d="scan'208";a="190575105" Date: Wed, 23 Sep 2009 09:27:00 +0800 From: Wu Fengguang To: Andrew Morton Cc: Chris Mason , Peter Zijlstra , "Li, Shaohua" , "linux-kernel@vger.kernel.org" , "richard@rsk.demon.co.uk" , "jens.axboe@oracle.com" Subject: Re: regression in page writeback Message-ID: <20090923012700.GA10464@localhost> References: <20090922054913.GA27260@sli10-desk.sh.intel.com> <1253601612.8439.274.camel@twins> <20090922080505.GB9192@localhost> <1253606965.8439.281.camel@twins> <20090922082427.GA24888@localhost> <1253608335.8439.283.camel@twins> <20090922155259.GL10825@think> <20090923002220.GA6382@localhost> <20090922175452.d66400dd.akpm@linux-foundation.org> <20090923011758.GC6382@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090923011758.GC6382@localhost> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3184 Lines: 101 On Wed, Sep 23, 2009 at 09:17:58AM +0800, Wu Fengguang wrote: > On Wed, Sep 23, 2009 at 08:54:52AM +0800, Andrew Morton wrote: > > On Wed, 23 Sep 2009 08:22:20 +0800 Wu Fengguang wrote: > > > > > Jens' per-bdi writeback has another improvement. In 2.6.31, when > > > superblocks A and B both have 100000 dirty pages, it will first > > > exhaust A's 100000 dirty pages before going on to sync B's. > > > > That would only be true if someone broke 2.6.31. Did they? > > > > SYSCALL_DEFINE0(sync) > > { > > wakeup_pdflush(0); > > sync_filesystems(0); > > sync_filesystems(1); > > if (unlikely(laptop_mode)) > > laptop_sync_completion(); > > return 0; > > } > > > > the sync_filesystems(0) is supposed to non-blockingly start IO against > > all devices. It used to do that correctly. But people mucked with it > > so perhaps it no longer does. > > I'm referring to writeback_inodes(). Each invocation of which (to sync > 4MB) will do the same iteration over superblocks A => B => C ... So if > A has dirty pages, it will always be served first. > > So if wbc->bdi == NULL (which is true for kupdate/background sync), it > will have to first exhaust A before going on to B and C. > > There are no "cursor" in the superblock level iterations. I even have an old patch for it. But Jens' patches are more general solution. Thanks, Fengguang --- writeback: continue from the last super_block in syncing Cc: David Chinner Cc: Michael Rubin Cc: Peter Zijlstra Signed-off-by: Fengguang Wu --- fs/fs-writeback.c | 12 ++++++++++++ include/linux/writeback.h | 2 ++ 2 files changed, 14 insertions(+) --- linux-2.6.orig/fs/fs-writeback.c +++ linux-2.6/fs/fs-writeback.c @@ -494,11 +494,19 @@ void writeback_inodes(struct writeback_control *wbc) { struct super_block *sb; + int i; + + if (wbc->sb_index) + wbc->more_io = 1; might_sleep(); spin_lock(&sb_lock); restart: + i = -1; list_for_each_entry_reverse(sb, &super_blocks, s_list) { + i++; + if (i < wbc->sb_index) + continue; if (sb_has_dirty_inodes(sb)) { /* we're making our own get_super here */ sb->s_count++; @@ -520,9 +528,13 @@ restart: if (__put_super_and_need_restart(sb)) goto restart; } + if (list_empty(&sb->s_io)) + wbc->sb_index++; if (wbc->nr_to_write <= 0) break; } + if (&sb->s_list == &super_blocks) + wbc->sb_index = 0; spin_unlock(&sb_lock); } --- linux-2.6.orig/include/linux/writeback.h +++ linux-2.6/include/linux/writeback.h @@ -48,6 +48,8 @@ struct writeback_control { this for each page written */ long pages_skipped; /* Pages which were not written */ + int sb_index; /* the superblock to continue from */ + /* * For a_ops->writepages(): is start or end are non-zero then this is * a hint that the filesystem need only write out the pages inside that -- 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/