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Wed, 15 Nov 2023 14:20:40 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EACB22004B; Wed, 15 Nov 2023 14:20:39 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2A43C20043; Wed, 15 Nov 2023 14:20:37 +0000 (GMT) Received: from li-2b55cdcc-350b-11b2-a85c-a78bff51fc11.ibm.com (unknown [9.171.69.220]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTPS; Wed, 15 Nov 2023 14:20:37 +0000 (GMT) Date: Wed, 15 Nov 2023 15:20:35 +0100 From: Sumanth Korikkar To: David Hildenbrand Cc: linux-mm , Andrew Morton , Oscar Salvador , Michal Hocko , "Aneesh Kumar K.V" , Anshuman Khandual , Gerald Schaefer , Alexander Gordeev , Heiko Carstens , Vasily Gorbik , linux-s390 , LKML Subject: Re: [PATCH 6/8] s390/mm: implement MEM_PHYS_ONLINE MEM_PHYS_OFFLINE memory notifiers Message-ID: References: <20231114180238.1522782-1-sumanthk@linux.ibm.com> <20231114180238.1522782-7-sumanthk@linux.ibm.com> <458da84d-3838-4c5d-abda-1aebba676186@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <458da84d-3838-4c5d-abda-1aebba676186@redhat.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 9b7dDx8KFTNFeVw7B4-xj3v6fwtslpa4 X-Proofpoint-GUID: OUd9BhB4V8HkjqGLN8EGhtJyl8CYuEGq X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.987,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-11-15_13,2023-11-15_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 suspectscore=0 mlxlogscore=609 spamscore=0 clxscore=1015 adultscore=0 mlxscore=0 bulkscore=0 impostorscore=0 malwarescore=0 phishscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311060000 definitions=main-2311150111 X-Rspamd-Queue-Id: 644EFC0027 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 7xb9i935kgu9egzwm3fmwj4i5x6p3zkf X-HE-Tag: 1700058047-619415 X-HE-Meta: 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 RiuZ82Dj +nr8sZJeOfO3Susg8dvG5ozDh5/EqZMY61bnwMVWBsOJvzg2k1fWQqG997mX6jH+Ou09eQBz4SG1dhA+MWE7rteBGciQIao2KIW7b2Z/z1ogaZk4Hep8o0giCUgQFdXIOWEoGo87sSblvmqhuqhR7p55VZ8GIYN8KA8CyEP0Pvo6qVCRuvDzQnM86/g== 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: List-Subscribe: List-Unsubscribe: On Tue, Nov 14, 2023 at 07:39:40PM +0100, David Hildenbrand wrote: > On 14.11.23 19:02, Sumanth Korikkar wrote: > > Implement MEM_PHYS_ONLINE and MEM_PHYS_OFFLINE memory notifiers on s390 > > ... > > arch/s390/mm/init.c | 16 +++++++++++++++- > > drivers/s390/char/sclp_cmd.c | 33 ++++++++++++++++++++++++++++++--- > > 2 files changed, 45 insertions(+), 4 deletions(-) > > > > diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c > > index 8d9a60ccb777..db505ed590b2 100644 > > --- a/arch/s390/mm/init.c > > +++ b/arch/s390/mm/init.c > > @@ -288,6 +288,12 @@ int arch_add_memory(int nid, u64 start, u64 size, > > rc = vmem_add_mapping(start, size); > > if (rc) > > return rc; > > + /* > > + * If MHP_MEMMAP_ON_MEMORY is enabled, perform __add_pages() during memory > > + * onlining phase > > + */ > > + if (params->altmap) > > + return 0; > > > So we'd have added memory blocks without a memmap? Sorry, but this seems to > further hack into the s390x direction. This new approach has the advantage that we do not need to allocate any additional memory during online phase, neither for direct mapping page tables nor struct pages, so that memory hotplug can never fail. The old approach (without altmap) is already a hack, because we add the memmap / struct pages, but for memory that is not really accessible. And with all the disadvantage of pre-allocating struct pages from system memory. The new approach allows to better integrate s390 to the existing interface, and also make use of altmap support, which would eliminate the major disadvantage of the old behaviour. So from s390 perspective, this new mechanism would be preferred, provided that there is no functional issue with the "added memory blocks without a memmap" approach. Do you see any functional issues, e.g. conflict with common code? > > Maybe s390x should just provide a dedicate interface to add these memory > blocks instead of adding them during boot and then relying on the old way of > using online/offline set them online/offline. Existing behavior: The current 'lsmem -a' command displays both online and standby memory. interface changes: If a new interface is introduced and standby memory is no longer listed, the following consequences might occur: 1. Running 'lsmem -a' would only show online memory, potentially leading to user complaints. 2. standby memory addition would need: * echo "standby memory addr" > /sys/devices/system/memory/probe As far as I understand, this interface is already deprecated. 3. To remove standby memory, a new interface probe_remove is needed * echo "standby memory addr" > /sys/devices/system/memory/probe_remove 4. Users may express a need to identify standby memory addresses, resulting in the creation of another interface to list these standby memory ranges. Hence, introducing new physical memory notifiers to platforms lacking dynamic ACPI events would be highly advantageous while maintaining existing user-friendly interface. Thanks