From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934223AbcHDSxk (ORCPT ); Thu, 4 Aug 2016 14:53:40 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:14746 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S934070AbcHDSxj (ORCPT ); Thu, 4 Aug 2016 14:53:39 -0400 X-IBM-Helo: d23dlp02.au.ibm.com X-IBM-MailFrom: hbathini@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Subject: Re: [RESEND][PATCH v2 2/2] powerpc/fadump: parse fadump reserve memory size based on memory range To: Michael Ellerman , rusty@rustcorp.com.au, ebiederm@xmission.com, vgoyal@redhat.com, linuxppc-dev References: <147025270324.29229.8322429758761407397.stgit@hbathini.in.ibm.com> <147025281599.29229.9962999599360876220.stgit@hbathini.in.ibm.com> <87h9b0g953.fsf@concordia.ellerman.id.au> Cc: Mahesh J Salgaonkar , kexec@lists.infradead.org, lkml , Ananth N Mavinakayanahalli From: Hari Bathini Date: Fri, 5 Aug 2016 00:23:26 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <87h9b0g953.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16080418-0044-0000-0000-000001CA2DED X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16080418-0045-0000-0000-00000542AA4B Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-08-04_11:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1608040204 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 04 August 2016 03:15 PM, Michael Ellerman wrote: > Hari Bathini writes: > ... >> /** >> * fadump_calculate_reserve_size(): reserve variable boot area 5% of System RAM >> * >> @@ -212,12 +262,17 @@ static inline unsigned long fadump_calculate_reserve_size(void) >> { >> unsigned long size; >> >> + /* sets fw_dump.reserve_bootvar */ >> + parse_fadump_reserve_mem(); >> + >> /* >> * Check if the size is specified through fadump_reserve_mem= cmdline >> * option. If yes, then use that. >> */ >> if (fw_dump.reserve_bootvar) >> return fw_dump.reserve_bootvar; >> + else >> + printk(KERN_INFO "fadump: calculating default boot size\n"); >> >> /* divide by 20 to get 5% of value */ >> size = memblock_end_of_DRAM() / 20; > The code already knows how to reserve 5% based on the size of the machine's > memory, as long as no commandline parameter is passed. So why can't we > just use that logic? Hi Michael, That is the default value reserved but not a good enough value for every case. It is a bit difficult to come up with a robust formula that works for every case as new kernel changes could make the values obsolete. But it won't be all that difficult to find values that work for different memory ranges for a given kernel version. Passing that as range based input with "fadump_reserve_mem" parameter would work for every memory configuration on a given system, which is what this patch is trying to provide.. Thanks Hari > cheers >