From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 42555ECDFAA for ; Mon, 16 Jul 2018 08:26:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DF38720779 for ; Mon, 16 Jul 2018 08:26:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DF38720779 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728495AbeGPIxG (ORCPT ); Mon, 16 Jul 2018 04:53:06 -0400 Received: from mx2.suse.de ([195.135.220.15]:51092 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726190AbeGPIxG (ORCPT ); Mon, 16 Jul 2018 04:53:06 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id A932AAE61; Mon, 16 Jul 2018 08:26:48 +0000 (UTC) Date: Mon, 16 Jul 2018 10:26:46 +0200 From: Michal Hocko To: Mahesh J Salgaonkar Cc: linuxppc-dev , Linux Kernel , Hari Bathini , Ananth N Mavinakayanahalli , Srikar Dronamraju , "Aneesh Kumar K.V" , Anshuman Khandual , Andrew Morton , Joonsoo Kim , Ananth Narayan , kernelfans@gmail.com Subject: Re: [RFC PATCH v6 0/4] powerpc/fadump: Improvements and fixes for firmware-assisted dump. Message-ID: <20180716082646.GF17280@dhcp22.suse.cz> References: <153172096333.29252.4376707071382727345.stgit@jupiter.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <153172096333.29252.4376707071382727345.stgit@jupiter.in.ibm.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 16-07-18 11:32:56, Mahesh J Salgaonkar wrote: > One of the primary issues with Firmware Assisted Dump (fadump) on Power > is that it needs a large amount of memory to be reserved. This reserved > memory is used for saving the contents of old crashed kernel's memory before > fadump capture kernel uses old kernel's memory area to boot. However, This > reserved memory area stays unused until system crash and isn't available > for production kernel to use. How much memory are we talking about. Regular kernel dump process needs some reserved memory as well. Why that is not a big problem? > Instead of setting aside a significant chunk of memory that nobody can use, > take advantage ZONE_MOVABLE to mark a significant chunk of reserved memory > as ZONE_MOVABLE, so that the kernel is prevented from using, but > applications are free to use it. Why kernel cannot use that memory while userspace can? [...] > Documentation/powerpc/firmware-assisted-dump.txt | 18 +++ > arch/powerpc/include/asm/fadump.h | 7 + > arch/powerpc/kernel/fadump.c | 123 +++++++++++++++++-- > arch/powerpc/platforms/pseries/hotplug-memory.c | 7 + > include/linux/mmzone.h | 2 > mm/page_alloc.c | 146 ++++++++++++++++++++++ > 6 files changed, 290 insertions(+), 13 deletions(-) This is quite a large change and you didn't seem to explain why we need it. -- Michal Hocko SUSE Labs