Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753150AbdFRWVm (ORCPT ); Sun, 18 Jun 2017 18:21:42 -0400 Received: from mail-pf0-f170.google.com ([209.85.192.170]:35411 "EHLO mail-pf0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752503AbdFRWVj (ORCPT ); Sun, 18 Jun 2017 18:21:39 -0400 Subject: Re: attempting to format brd device results in OOM kills To: Jeff Layton , Christoph Hellwig Cc: Hannes Reinecke , LKML References: <1497803428.21567.4.camel@redhat.com> From: Jens Axboe Message-ID: <7e8cdef3-7062-0a11-63c1-e19fabcd117c@kernel.dk> Date: Sun, 18 Jun 2017 16:21:36 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <1497803428.21567.4.camel@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1338 Lines: 42 On 06/18/2017 10:30 AM, Jeff Layton wrote: > I've run across a regression from v4.11. If I boot a v4.12-rc1 or later > kernel, make a large brd device and try to format it, it quickly slows > down to a crawl and then the OOM killer kicks in. > > I ran a bisect and it landed here: > > commit f09a06a193d942a12c1a33c153388b3962222006 (HEAD, refs/bisect/bad) > Author: Christoph Hellwig > Date: Wed Apr 5 19:21:16 2017 +0200 > > brd: remove discard support > > It's just a in-driver reimplementation of writing zeroes to the pages, > which fails if the discards aren't page aligned. > > Signed-off-by: Christoph Hellwig > Reviewed-by: Hannes Reinecke > Signed-off-by: Jens Axboe > > > I've been reproducing it in a VM with ~8G allocated to it: > > I have a modprobe.d file with this in it: > > options brd rd_nr=1 rd_size=1073741824 > > I then just: > > # modprobe brd > # mkfs -t ext2 /dev/ram0 > > It keels over pretty quickly after that. Just checked, and creating a 1TB ram disk and then running mkfs.ext2 on it writes 16851MiB of data. I can't say I'm surprised you OOM, if you run that in a 8G VM, as you're about 8G short. I'm puzzled as to why the discard change would make any difference, however. -- Jens Axboe