From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755706AbdKNPxx (ORCPT ); Tue, 14 Nov 2017 10:53:53 -0500 Received: from mx2.suse.de ([195.135.220.15]:49838 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755654AbdKNPxa (ORCPT ); Tue, 14 Nov 2017 10:53:30 -0500 Date: Tue, 14 Nov 2017 15:53:27 +0000 From: Mel Gorman To: YASUAKI ISHIMATSU Cc: rostedt@goodmis.org, mingo@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, koki.sanagi@us.fujitsu.com Subject: Re: Allocation failure of ring buffer for trace Message-ID: <20171114155327.5ugozxxsofqoohv2@suse.de> References: <9631b871-99cc-82bb-363f-9d429b56f5b9@gmail.com> <20171114114633.6ltw7f4y7qwipcqp@suse.de> <48b66fc4-ef82-983c-1b3d-b9c0a482bc51@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <48b66fc4-ef82-983c-1b3d-b9c0a482bc51@gmail.com> User-Agent: NeoMutt/20170421 (1.8.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 14, 2017 at 10:39:19AM -0500, YASUAKI ISHIMATSU wrote: > > > On 11/14/2017 06:46 AM, Mel Gorman wrote: > > On Mon, Nov 13, 2017 at 12:48:36PM -0500, YASUAKI ISHIMATSU wrote: > >> When using trace_buf_size= boot option, memory allocation of ring buffer > >> for trace fails as follows: > >> > >> [ ] x86: Booting SMP configuration: > >> > >> > >> In my server, there are 384 CPUs, 512 GB memory and 8 nodes. And > >> "trace_buf_size=100M" is set. > >> > >> When using trace_buf_size=100M, kernel allocates 100 MB memory > >> per CPU before calling free_are_init_core(). Kernel tries to > >> allocates 38.4GB (100 MB * 384 CPU) memory. But available memory > >> at this time is about 16GB (2 GB * 8 nodes) due to the following commit: > >> > >> 3a80a7fa7989 ("mm: meminit: initialise a subset of struct pages > >> if CONFIG_DEFERRED_STRUCT_PAGE_INIT is set") > >> > > > > 1. What is the use case for such a large trace buffer being allocated at > > boot time? > > I'm not sure the use case. I found the following commit log: > > commit 864b9a393dcb5aed09b8fd31b9bbda0fdda99374 > Author: Michal Hocko > Date: Fri Jun 2 14:46:49 2017 -0700 > > mm: consider memblock reservations for deferred memory initialization sizing > > So I thought similar memory exhaustion may occurs on other boot option. > And I reproduced the issue. > That was different, it was a premature OOM caused by reservations that were of a known size. It's not related to trace_buf_size in any fashion. > > > 2. Is disabling CONFIG_DEFERRED_STRUCT_PAGE_INIT at compile time an > > option for you given that it's a custom-built kernel and not a > > distribution kernel? > > The issue also occurred on distribution kernels. So we have to fix the issue. > I'm aware of now bugs against a distribution kernel. However, does the patch work for you? -- Mel Gorman SUSE Labs