From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f52.google.com (mail-wg0-f52.google.com [74.125.82.52]) by kanga.kvack.org (Postfix) with ESMTP id 0170E900018 for ; Tue, 11 Nov 2014 16:16:18 -0500 (EST) Received: by mail-wg0-f52.google.com with SMTP id b13so12424524wgh.11 for ; Tue, 11 Nov 2014 13:16:17 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id j16si24777367wic.43.2014.11.11.13.16.17 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 11 Nov 2014 13:16:17 -0800 (PST) Date: Tue, 11 Nov 2014 22:16:15 +0100 From: Jan Kara Subject: Re: [BUG] mm/page-writeback.c: divide by zero in pos_ratio_polynom not fixed Message-ID: <20141111211615.GE32298@quack.suse.cz> References: <20141101082325.7be0463f@gandalf.local.home> <20141111201539.GA12333@quack.suse.cz> <20141111160448.61354836@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141111160448.61354836@gandalf.local.home> Sender: owner-linux-mm@kvack.org List-ID: To: Steven Rostedt Cc: Jan Kara , Rik van Riel , LKML , Michal Hocko , linux-mm@kvack.org, Mel Gorman , Andrew Morton On Tue 11-11-14 16:04:48, Steven Rostedt wrote: > On Tue, 11 Nov 2014 21:15:39 +0100 > Jan Kara wrote: > > > > So I was looking into this but I have to say I don't understand where is > > the problem. The registers clearly show that x_intercept - bdi_setpoint + 1 > > == 0 (in 32-bit arithmetics). Given: > > x_intercept = bdi_setpoint + span > > > > We have that span + 1 == 0 and that means that: > > ((thresh - bdi_thresh + 8 * write_bw) * (u64)x >> 16) == -1 (again in > > 32-bit arithmetics). But I don't see how that can realistically happen... > > > > Is this reproducible at all? > > > > Unfortunately not. It only happened once, and I haven't been able to > reproduce it again. BTW, how much memory does the machine have and what is /proc/sys/vm/dirty_ratio and /proc/sys/vm/dirty_background_ratio (or corresponding dirty_bytes, dirty_background_bytes if you are using them)? Honza -- Jan Kara SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org