From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vojtech Pavlik Subject: Re: Bcache stuck at writeback of a key, consuming 100% CPU, not possible to detach Date: Mon, 31 Aug 2015 18:54:30 +0200 Message-ID: <20150831165430.GA10258@suse.com> References: <20150830085442.GA31722@suse.com> <20150831163937.00ca3f7a@harpe.intellique.com> <20150831144949.GA3276@suse.com> <20150831150429.GA27538@kmo-pixel> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx2.suse.de ([195.135.220.15]:36547 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753302AbbHaQyc (ORCPT ); Mon, 31 Aug 2015 12:54:32 -0400 Content-Disposition: inline In-Reply-To: <20150831150429.GA27538@kmo-pixel> Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: Kent Overstreet Cc: Emmanuel Florac , linux-bcache@vger.kernel.org On Mon, Aug 31, 2015 at 07:04:29AM -0800, Kent Overstreet wrote: > I suspect there's two different bugs here. > > - I'm starting to suspect there's a bug in the dirty data accounting, and it's > getting out of sync - i.e. reading 2.8 GB or whatever when it's actually 0. > that would explain it spinning when there actually isn't any work for it to > do. > > - with a large enough amount of data, the 30 second writeback_delay may be > insufficient; if it takes longer than that just to scan the entire keyspace > it'll never get a chance to sleep. try bumping writeback_delay up and see if > that helps. > > the ratelimiting on scanning for dirty data needs to be changed to something > more sophisticated, the existing fixed delay is problematic. Is there any difference regarding writeback problems between using 4.1.6 and your bcache-dev git branch? It may take a bit of effort, but I should be able to get bcache-dev installed on my system. -- Vojtech Pavlik Director SuSE Labs