Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752861AbcLHSgF (ORCPT ); Thu, 8 Dec 2016 13:36:05 -0500 Received: from mail-oi0-f53.google.com ([209.85.218.53]:35673 "EHLO mail-oi0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751388AbcLHSgE (ORCPT ); Thu, 8 Dec 2016 13:36:04 -0500 MIME-Version: 1.0 X-Originating-IP: [2604:ba00:2:1:1d95:c3b0:3b1a:2454] From: Robert LeBlanc Date: Thu, 8 Dec 2016 11:36:03 -0700 Message-ID: Subject: crashkernel only allowing smaller allocations as kernel version increases To: "Linux-Kernel@Vger. Kernel. Org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1184 Lines: 34 I've been trying to capture a core to help in debuging a problem, but it seems that as I go up in kernel versions, I can only allocate less and less memory to crashkernel and with 4.9-rc8 I can't allocate enough to prevent OOM (specifically on CentOS with iSCSI root). I'm seeing the same reduction of allocatable memory on both Debian and CentOS on the same hardware As an example: Debian 3.16 - 1 GB is OK 4.9-rc7 - ~512MB is OK, but gets "kernel version is not supported". CentOS 3.10 - 1 GB is OK 4.8 - ~800MB is OK 4.9-rc8 - ~512MB is OK, but OOMs CentOS 4.9 kernel was built with default config, Debian 4.9 was built by coping the distro 3.16.0-4 config and then running make menuconfig. Trying to specify memory amount above this causes kdump to report that no memory has been reserved. The hardware has 512GB of RAM. Am I missing some config option that limiting how much crashkernel can reserve? I also verified on my test desktop with 8GB of RAM that setting crashkernel=1024M also fails to allocate memory with 4.9-rc8, but works fine with 128M for instance. Thanks, ---------------- Robert LeBlanc PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1