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Tue, 1 Aug 2023 09:28:33 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DB4612004B; Tue, 1 Aug 2023 09:28:32 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9E44220043; Tue, 1 Aug 2023 09:28:30 +0000 (GMT) Received: from [9.43.52.167] (unknown [9.43.52.167]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 1 Aug 2023 09:28:30 +0000 (GMT) Message-ID: Date: Tue, 1 Aug 2023 14:58:29 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v7 7/7] mm/memory_hotplug: Enable runtime update of memmap_on_memory parameter To: Michal Hocko References: <20230801044116.10674-1-aneesh.kumar@linux.ibm.com> <20230801044116.10674-8-aneesh.kumar@linux.ibm.com> Content-Language: en-US From: Aneesh Kumar K V In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: fCwk6B3C8CVsWbV82uf81AkO2vq9Jwjy X-Proofpoint-GUID: 9GIdpCQkNLtnf3QJy6rfiC7G64hIHQLH X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.957,Hydra:6.0.591,FMLib:17.11.176.26 definitions=2023-08-01_03,2023-07-31_02,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 mlxscore=0 bulkscore=0 adultscore=0 malwarescore=0 mlxlogscore=552 lowpriorityscore=0 suspectscore=0 clxscore=1015 spamscore=0 phishscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2306200000 definitions=main-2308010082 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Hildenbrand , linux-mm@kvack.org, npiggin@gmail.com, Vishal Verma , akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, Oscar Salvador Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 8/1/23 2:28 PM, Michal Hocko wrote: > On Tue 01-08-23 10:11:16, Aneesh Kumar K.V wrote: >> Allow updating memmap_on_memory mode after the kernel boot. Memory >> hotplug done after the mode update will use the new mmemap_on_memory >> value. > > Well, this is a user space kABI extension and as such you should spend > more words about the usecase. Why we could live with this static and now > need dynamic? > This enables easy testing of memmap_on_memory feature without a kernel reboot. I also expect people wanting to use that when they find dax kmem memory online failing because of struct page allocation failures[1]. User could reboot back with memmap_on_memory=y kernel parameter. But being able to enable it via sysfs makes the feature much more useful. -aneesh