From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: Re: [PATCH 3/9] writeback: bdi write bandwidth estimation Date: Sat, 23 Jul 2011 16:07:21 +0800 Message-ID: <20110723080721.GC31975@localhost> References: <20110629145245.835998321@intel.com> <20110629145553.906668553@intel.com> <20110701192915.GE28563@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "linux-fsdevel@vger.kernel.org" , Jan Kara , Dave Chinner , Christoph Hellwig , Andrew Morton , "Li, Shaohua" , Peter Zijlstra , LKML To: Vivek Goyal Return-path: Received: from mga03.intel.com ([143.182.124.21]:33872 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751471Ab1GWIHe (ORCPT ); Sat, 23 Jul 2011 04:07:34 -0400 Content-Disposition: inline In-Reply-To: <20110701192915.GE28563@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Sat, Jul 02, 2011 at 03:29:15AM +0800, Vivek Goyal wrote: > On Wed, Jun 29, 2011 at 10:52:48PM +0800, Wu Fengguang wrote: > > The estimation value will start from 100MB/s and adapt to the real > > bandwidth in seconds. > > > > It tries to update the bandwidth only when disk is fully utilized. > > Any inactive period of more than one second will be skipped. > > Is this piece of code being tested in your graphs? Are there any > inactive periods which get filtered out in your workload? I am > assuming in a continuous dd, we will not have periods of inactivity > 1 second long. There are no inactive periods in the dd tests. However I did try "watch cat /debug/bdi/8:0/stats" while starting some write workloads in background. When the write stops, the bandwidth does stop updating. Thanks, Fengguang