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Wed, 10 Jun 2020 11:45:28 +0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 05ABjPtt56623548 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 10 Jun 2020 11:45:25 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 51090AE045; Wed, 10 Jun 2020 11:45:25 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DF756AE04D; Wed, 10 Jun 2020 11:45:24 +0000 (GMT) Received: from osiris (unknown [9.171.62.218]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Wed, 10 Jun 2020 11:45:24 +0000 (GMT) Date: Wed, 10 Jun 2020 13:45:23 +0200 From: Heiko Carstens To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, Vasily Gorbik , Christian Borntraeger , Philipp Rudo , Kirill Smelkov , Alexander Egorenkov Subject: Re: [PATCH RFC 1/2] s390/zcore: traverse resources instead of memblocks Message-ID: <20200610114523.GA5943@osiris> References: <20200417150151.17239-1-david@redhat.com> <20200417150151.17239-2-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200417150151.17239-2-david@redhat.com> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.687 definitions=2020-06-10_07:2020-06-10,2020-06-10 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 mlxlogscore=999 malwarescore=0 impostorscore=0 cotscore=-2147483648 suspectscore=1 mlxscore=0 clxscore=1011 adultscore=0 spamscore=0 bulkscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006100088 X-Rspamd-Queue-Id: C62A010045C16 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Apr 17, 2020 at 05:01:50PM +0200, David Hildenbrand wrote: > The zcore memmap basically contains the first level of all system RAM from > /proc/iomem. We want to disable CONFIG_ARCH_KEEP_MEMBLOCK (e.g., to not > create memblocks for hotplugged/standby memory and save space), switch to > traversing system ram resources instead. During early boot, we create > resources for all early memblocks (including the crash kernel area). When > adding standby memory, we currently create both, memblocks and resources. > > Note: As we don't have memory hotplug after boot (standby memory is added > via sclp during boot), we don't have to worry about races. > > I am only able to test under KVM (where I hacked up zcore to still > create the memmap file) > > root@vm0:~# cat /proc/iomem > 00000000-2fffffff : System RAM > 10424000-10ec6fff : Kernel code > 10ec7000-1139a0e3 : Kernel data > 1177a000-11850fff : Kernel bss > 30000000-3fffffff : Crash kernel > > Result without this patch: > root@vm0:~# cat /sys/kernel/debug/zcore/memmap > 0000000000000000 0000000040000000 > > Result with this patch: > root@vm0:~# cat /sys/kernel/debug/zcore/memmap > 0000000000000000 0000000030000000 0000000030000000 0000000010000000 > > The difference is due to memblocks getting merged, resources (currently) > not. So we might have some more entries, but they describe the same > memory map. > > Cc: Heiko Carstens > Cc: Vasily Gorbik > Cc: Christian Borntraeger > Cc: Philipp Rudo > Cc: Kirill Smelkov > Cc: Michael Holzheu > Signed-off-by: David Hildenbrand > --- > drivers/s390/char/zcore.c | 61 ++++++++++++++++++++++++++++++--------- > 1 file changed, 48 insertions(+), 13 deletions(-) I'm having a hard time to find any code that ever made use of this file. After all this was only meant for our zfcp dumper, but as far as I can tell there was never code out there that read the memmap file. So the pragmatic approach would be to just change its contents, or a more progressive variant would be to remove the file completely. But maybe I'm entirely wrong... I'm leaving this up to Philipp and Alexander :)