From mboxrd@z Thu Jan 1 00:00:00 1970 From: Larkin Lowrey Subject: Slow writing of dirty data (bcache) Date: Mon, 10 Mar 2014 11:34:45 -0500 Message-ID: <531DE9A5.90801@nuclearwinter.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from titan.nuclearwinter.com ([174.136.96.186]:50594 "EHLO mail.nuclearwinter.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753362AbaCJRHV (ORCPT ); Mon, 10 Mar 2014 13:07:21 -0400 Received: from [IPv6:2601:e:1200:c80:52e5:49ff:febe:9a2b] ([IPv6:2601:e:1200:c80:52e5:49ff:febe:9a2b]) (authenticated bits=0) by mail.nuclearwinter.com (8.14.4/8.14.4) with ESMTP id s2AGYgYn015143 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO) for ; Mon, 10 Mar 2014 11:34:43 -0500 Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: linux-bcache@vger.kernel.org I'm seeing an odd behavior after updating to kernel 3.13.5-202.fc20.x86_64 from 3.12.7-300.fc20.x86_64. I have a bcache device (bcache2) which backs a raid5 array (md2) that has 160+MB of dirty data. The dirty data is being written at a rate of 1 page per second (8 sectors). At this rate it'll take 11 hrs to finish. I like to keep this array spun down when inactive but the drives can't spin down since they're being written to once a second. # cat /sys/block/bcache2/bcache/writeback_rate 512 # cat /sys/block/bcache2/bcache/writeback_rate_debug rate: 512/sec dirty: 161M target: 40.8G proportional: -35.2M derivative: 0 change: -35.2M/sec next io: 624ms This never happened when running 3.12.7. Is there anything I can do about this? --Larkin