From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751955AbaAXWwL (ORCPT ); Fri, 24 Jan 2014 17:52:11 -0500 Received: from zene.cmpxchg.org ([85.214.230.12]:52237 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751087AbaAXWwH (ORCPT ); Fri, 24 Jan 2014 17:52:07 -0500 Date: Fri, 24 Jan 2014 17:51:56 -0500 From: Johannes Weiner To: Andrew Morton Cc: Tejun Heo , Rik van Riel , Mel Gorman , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [patch 0/2] mm: reduce reclaim stalls with heavy anon and dirty cache Message-ID: <20140124225156.GG4407@cmpxchg.org> References: <1390600984-13925-1-git-send-email-hannes@cmpxchg.org> <20140124143003.2629e9c2c8c2595e805c8c25@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140124143003.2629e9c2c8c2595e805c8c25@linux-foundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 24, 2014 at 02:30:03PM -0800, Andrew Morton wrote: > On Fri, 24 Jan 2014 17:03:02 -0500 Johannes Weiner wrote: > > > Tejun reported stuttering and latency spikes on a system where random > > tasks would enter direct reclaim and get stuck on dirty pages. Around > > 50% of memory was occupied by tmpfs backed by an SSD, and another disk > > (rotating) was reading and writing at max speed to shrink a partition. > > Do you think this is serious enough to squeeze these into 3.14? We have been biasing towards cache reclaim at least as far back as the LRU split and we always considered anon dirtyable, so it's not really a *new* problem. And there is a chance of regressing write bandwidth for certain workloads by effectively shrinking their dirty limit - although that is easily fixed by changing dirty_ratio. On the other hand, the stuttering is pretty nasty (could reproduce it locally too) and the workload is not exactly esoteric. Plus, I'm not sure if waiting will increase the test exposure. So 3.14 would work for me, unless Mel and Rik have concerns.