From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: [PATCH 1/2] writeback: Improve busyloop prevention Date: Thu, 13 Oct 2011 22:18:35 +0200 Message-ID: <20111013201835.GD27363@quack.suse.cz> References: <1318453043-32057-1-git-send-email-jack@suse.cz> <1318453043-32057-2-git-send-email-jack@suse.cz> <20111013142638.GB6938@localhost> <20111013143939.GA9691@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , "linux-fsdevel@vger.kernel.org" , Christoph Hellwig , Dave Chinner To: Wu Fengguang Return-path: Received: from cantor2.suse.de ([195.135.220.15]:48653 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751702Ab1JMUSg (ORCPT ); Thu, 13 Oct 2011 16:18:36 -0400 Content-Disposition: inline In-Reply-To: <20111013143939.GA9691@localhost> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Thu 13-10-11 22:39:39, Wu Fengguang wrote: > > > + long pause = 1; > > > + long max_pause = dirty_writeback_interval ? > > > + msecs_to_jiffies(dirty_writeback_interval * 10) : > > > + HZ; > > > > It's better not to put the flusher to sleeps more than 10ms, so that > > when the condition changes, we don't risk making the storage idle for > > too long time. > > Yeah, the one big regression case > > 3.1.0-rc8-ioless6a+ 3.1.0-rc8-ioless6-requeue6+ > ------------------------ ------------------------ > 47.07 -15.5% 39.78 thresh=1M/xfs-2dd-4k-8p-4096M-1M:10-X > > is exactly caused by the large sleep: the attached graphs are showing > one period of no-progress on the number of written pages. Thanks for the tests! Interesting. Do you have trace file from that run? I see the writeback stalled for 20s or so which is more than dirty_writeback_centisecs so I think something more complicated must have happened. Honza -- Jan Kara SUSE Labs, CR