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Tue, 7 Oct 2025 14:30:22 +0000 (GMT) Date: Tue, 7 Oct 2025 16:30:21 +0200 From: Sumanth Korikkar To: Andrew Morton , David Hildenbrand , linux-mm Cc: LKML , linux-s390 , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Alexander Gordeev Subject: Re: [PATCH 0/4] Support dynamic (de)configuration of memory Message-ID: References: <20250926131527.3260733-1-sumanthk@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250926131527.3260733-1-sumanthk@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: PdkXKFhNzTG2BT8DipAPd1uZ87BQphbV X-Authority-Analysis: v=2.4 cv=BpiQAIX5 c=1 sm=1 tr=0 ts=68e52403 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=kj9zAlcOel0A:10 a=x6icFKpwvdMA:10 a=VwQbUJbxAAAA:8 a=20KFwNOVAAAA:8 a=VnNF1IyMAAAA:8 a=w9My_uIrVxvTaZuSxxAA:9 a=CjuIK1q_8ugA:10 a=HhbK4dLum7pmb74im6QT:22 a=cPQSjfK2_nFv0Q5t_7PE:22 a=pHzHmUro8NiASowvMSCR:22 a=Ew2E2A-JSTLzCXPT_086:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDA0MDAyMiBTYWx0ZWRfX/tzvw3cApgKZ ONyKqQVhsLg6ZJvP2trmG55xOCkFAKZ7rwkNlxFpvKy2DdcVbtpTE2QsTCCIuF5ZwONxvIu5fK6 OTJAy4WeFfjs6kdZz0a2Z8TiF2RP3FB110TP6GPoWYjNV64WXPcYHqcfNEj07g1dVRXNV1y/ZeA ORaL+5YDnl0Cjphe38y2uIOOmWkX2xRbgtnxtddU+96nHVBUKtHK6EToiaeVD7Xb0iYk8YfFdJk 2BwbeN6UXRxFQEr7kZ5S91yKpLmkyiV9mXqX1B8E5q4GKoLT1tdzOx0tZW04TkCC9FGTB8aP+A0 xixHAVY8S3Z8/IM2p7TKvjv/uwNJFpn1t0DfEd8xr50eP//PX56KYAUoeUrbIHdvDRgp+eRwF0j Lv9Nm2fMvHRvOCJ9ORwsT8v84u4ZGA== X-Proofpoint-ORIG-GUID: PdkXKFhNzTG2BT8DipAPd1uZ87BQphbV X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1117,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-10-07_01,2025-10-06_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 lowpriorityscore=0 priorityscore=1501 malwarescore=0 suspectscore=0 bulkscore=0 impostorscore=0 adultscore=0 clxscore=1015 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2509150000 definitions=main-2510040022 X-Stat-Signature: ym1ezbufaidxpjbpkpi6ppw3xh1urso8 X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 03CA4140023 X-HE-Tag: 1759847428-856002 X-HE-Meta: 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 NG8LLSCO BtbQvKLFRDtHWYSId085/LlJXLcjF+ufnWx4dSwDxNYFTLMyXbdJ3bYqmcr6mZn6AEVce2t3pPQkI7HPEWrESVZiqBnZTh4/r67utn96Y0m5c9/a/H42PLMNRKyF0jyWflKhmLY2AGB91P7a9Kx38ipvLVs0d2SSUL/yiGPPuEXQm8Csxf5VPctjvcVPMhg7/YZKw/4kZ56xspjua7jG7/d1md9pdvFQtFx8SjnJlkfL8Xs56o9r7CmnRtszjI5RWYk4SWNBRqfb2v0h3OoDc5S6s4uiMYO61vDryPctOQnVtN6SabSj+DkMOxzzK1riVkv85hRCPf33ft/m01MJ4iS/sD/Ts65LKk7VWu6bGML9GgbNNcB4BtMWrQxWo49BgcBts 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 Fri, Sep 26, 2025 at 03:15:23PM +0200, Sumanth Korikkar wrote: > Hi, > > Patchset provides a new interface for dynamic configuration and > deconfiguration of hotplug memory on s390, allowing with/without > memmap_on_memory support. It is a follow up on the discussion with David > when introducing memmap_on_memory support for s390 and support dynamic > (de)configuration of memory: > https://lore.kernel.org/all/ee492da8-74b4-4a97-8b24-73e07257f01d@redhat.com/ > https://lore.kernel.org/all/20241202082732.3959803-1-sumanthk@linux.ibm.com/ > > The original motivation for introducing memmap_on_memory on s390 was to > avoid using online memory to store struct pages metadata, particularly > for standby memory blocks. This became critical in cases where there was > an imbalance between standby and online memory, potentially leading to > boot failures due to insufficient memory for metadata allocation. > > To address this, memmap_on_memory was utilized on s390. However, in its > current form, it adds struct pages metadata at the start of each memory > block at the time of addition (only standby memory), and this > configuration is static. It cannot be changed at runtime (When the user > needs continuous physical memory). > > Inorder to provide more flexibility to the user and overcome the above > limitation, add an option to dynamically configure and deconfigure > hotpluggable memory block with/without memmap_on_memory. > > With the new interface, s390 will not add all possible hotplug memory in > advance, like before, to make it visible in sysfs for online/offline > actions. Instead, before memory block can be set online, it has to be > configured via a new interface in /sys/firmware/memory/memoryX/config, > which makes s390 similar to others. i.e. Adding of hotpluggable memory is > controlled by the user instead of adding it at boottime. Hi David, Looking forward to your feedback to proceed further. Thank you, Sumanth