From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f53.google.com (mail-pa0-f53.google.com [209.85.220.53]) by kanga.kvack.org (Postfix) with ESMTP id B068E6B0038 for ; Fri, 18 Sep 2015 10:50:44 -0400 (EDT) Received: by padhk3 with SMTP id hk3so53112996pad.3 for ; Fri, 18 Sep 2015 07:50:44 -0700 (PDT) Received: from mga14.intel.com (mga14.intel.com. [192.55.52.115]) by mx.google.com with ESMTP id i10si14100693pat.184.2015.09.18.07.50.43 for ; Fri, 18 Sep 2015 07:50:43 -0700 (PDT) Subject: Re: 4.3-rc1 dirty page count underflow (cgroup-related?) References: <55FB9319.2010000@intel.com> From: Dave Hansen Message-ID: <55FC24C2.8020501@intel.com> Date: Fri, 18 Sep 2015 07:50:42 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Greg Thelen Cc: Johannes Weiner , Michal Hocko , Tejun Heo , Jens Axboe , Andrew Morton , Jan Kara , "open list:CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)" , "open list:CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)" , open list On 09/17/2015 11:09 PM, Greg Thelen wrote: > I'm not denying the issue, bug the WARNING splat isn't necessarily > catching a problem. The corresponding code comes from your debug patch: > + WARN_ONCE(__this_cpu_read(memcg->stat->count[MEM_CGROUP_STAT_DIRTY]) > (1UL<<30), "MEM_CGROUP_STAT_DIRTY bogus"); > > This only checks a single cpu's counter, which can be negative. The sum > of all counters is what matters. > Imagine: > cpu1) dirty page: inc > cpu2) clean page: dec > The sum is properly zero, but cpu2 is -1, which will trigger the WARN. > > I'll look at the code and also see if I can reproduce the failure using > mem_cgroup_read_stat() for all of the new WARNs. D'oh. I'll replace those with the proper mem_cgroup_read_stat() and test with your patch to see if anything still triggers. > Did you notice if the global /proc/meminfo:Dirty count also underflowed? It did not underflow. It was one of the first things I looked at and it looked fine, went down near 0 at 'sync', etc... -- 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