From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:46721 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933242AbcIVO3H (ORCPT ); Thu, 22 Sep 2016 10:29:07 -0400 Subject: Re: deadlock with btrfs heavy i/o and kswapd To: Stefan Priebe - Profihost AG , "linux-btrfs@vger.kernel.org" References: <281582c9-1307-612e-77e6-9d768337ea3e@profihost.ag> From: Chris Mason Message-ID: <8116272d-6c30-431a-c3e1-781b17bea2c6@fb.com> Date: Thu, 22 Sep 2016 10:28:43 -0400 MIME-Version: 1.0 In-Reply-To: <281582c9-1307-612e-77e6-9d768337ea3e@profihost.ag> Content-Type: text/plain; charset="utf-8"; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 09/22/2016 02:41 AM, Stefan Priebe - Profihost AG wrote: > Hi, > > i always encounter btrfs deadlocks / hung tasks, when i have a lot of > cached mem and i'm doing heavy rsync --inplace operations in my system > from btrfs zlib compressed disk A to btrfs zlib compressed disk B. > > The last output i see in this case is kswapd0 running for a long time at > 100% cpu. Then the whole system get's stuck. I cannot connect to ssh > anymore but the kernel still prints hung tasks every few minutes. > > May be relevant the system has NO swap. > > vm.vfs_cache_pressure = 100 > vm.swappiness = 50 Are you able to capture the stack dumps? A sysrq-w would really help. -chris