From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933239Ab0GAVQV (ORCPT ); Thu, 1 Jul 2010 17:16:21 -0400 Received: from kroah.org ([198.145.64.141]:60923 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759012Ab0GAVNz (ORCPT ); Thu, 1 Jul 2010 17:13:55 -0400 X-Mailbox-Line: From gregkh@clark.site Thu Jul 1 10:42:53 2010 Message-Id: <20100701174253.521612891@clark.site> User-Agent: quilt/0.48-10.1 Date: Thu, 01 Jul 2010 10:42:54 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Jens Axboe Subject: [084/200] writeback: disable periodic old data writeback for !dirty_writeback_centisecs In-Reply-To: <20100701175201.GA2149@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.34-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jens Axboe commit 69b62d01ec44fe0d505d89917392347732135a4d upstream. Prior to 2.6.32, setting /proc/sys/vm/dirty_writeback_centisecs disabled periodic dirty writeback from kupdate. This got broken and now causes excessive sys CPU usage if set to zero, as we'll keep beating on schedule(). Reported-by: Justin Maggard Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- fs/fs-writeback.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -852,6 +852,12 @@ static long wb_check_old_data_flush(stru unsigned long expired; long nr_pages; + /* + * When set to zero, disable periodic writeback + */ + if (!dirty_writeback_interval) + return 0; + expired = wb->last_old_flush + msecs_to_jiffies(dirty_writeback_interval * 10); if (time_before(jiffies, expired)) @@ -947,8 +953,12 @@ int bdi_writeback_task(struct bdi_writeb break; } - wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10); - schedule_timeout_interruptible(wait_jiffies); + if (dirty_writeback_interval) { + wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10); + schedule_timeout_interruptible(wait_jiffies); + } else + schedule(); + try_to_freeze(); }