From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: [PATCH] writeback: Fix occasional slow sync(1) Date: Tue, 23 Jul 2013 18:16:05 +0200 Message-ID: <20130723161605.GA8282@quack.suse.cz> References: <1373881514-4214-1-git-send-email-jack@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org, Paul Taysom , Jan Kara To: Al Viro Return-path: Received: from cantor2.suse.de ([195.135.220.15]:47197 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932326Ab3GWQQI (ORCPT ); Tue, 23 Jul 2013 12:16:08 -0400 Content-Disposition: inline In-Reply-To: <1373881514-4214-1-git-send-email-jack@suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon 15-07-13 11:45:14, Jan Kara wrote: > In case when system contains no dirty pages, wakeup_flusher_threads() > will submit WB_SYNC_NONE writeback for 0 pages so wb_writeback() exits > immediately without doing anything. Thus sync(1) will write all the > dirty inodes from a WB_SYNC_ALL writeback pass which is slow. > > Fix the problem by using get_nr_dirty_pages() in > wakeup_flusher_threads() instead of calculating number of dirty pages > manually. That function also takes number of dirty inodes into account. > > CC: stable@vger.kernel.org > Reported-by: Paul Taysom > Signed-off-by: Jan Kara Ping Al? Honza > --- > fs/fs-writeback.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c > index a85ac4e..d0d70a8 100644 > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -1055,10 +1055,8 @@ void wakeup_flusher_threads(long nr_pages, enum wb_reason reason) > { > struct backing_dev_info *bdi; > > - if (!nr_pages) { > - nr_pages = global_page_state(NR_FILE_DIRTY) + > - global_page_state(NR_UNSTABLE_NFS); > - } > + if (!nr_pages) > + nr_pages = get_nr_dirty_pages(); > > rcu_read_lock(); > list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) { > -- > 1.8.1.4 > -- Jan Kara SUSE Labs, CR