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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 4 Jul 2019 12:30:20 +0100 Received: from b01ledav006.gho.pok.ibm.com (b01ledav006.gho.pok.ibm.com [9.57.199.111]) by b01cxnp22036.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x64BUJss13763534 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 4 Jul 2019 11:30:19 GMT Received: from b01ledav006.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C8679AC065; Thu, 4 Jul 2019 11:30:19 +0000 (GMT) Received: from b01ledav006.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 510ACAC059; Thu, 4 Jul 2019 11:30:18 +0000 (GMT) Received: from [9.85.88.166] (unknown [9.85.88.166]) by b01ledav006.gho.pok.ibm.com (Postfix) with ESMTP; Thu, 4 Jul 2019 11:30:17 +0000 (GMT) Subject: Re: [PATCH v2] powerpc/pseries: Fix maximum memory value To: Michael Ellerman , "Naveen N. Rao" , Nathan Lynch References: <156170480663.26214.11212383510892156924.stgit@aravinda> <87tvc9sjrb.fsf@linux.ibm.com> <1561743225.hrre8pgw6j.naveen@linux.ibm.com> <871rz6qch5.fsf@concordia.ellerman.id.au> From: Aravinda Prasad Date: Thu, 4 Jul 2019 17:00:16 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <871rz6qch5.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19070411-2213-0000-0000-000003A94988 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011377; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000286; SDB=6.01227282; UDB=6.00646184; IPR=6.01008520; MB=3.00027582; MTD=3.00000008; XFM=3.00000015; UTC=2019-07-04 11:30:21 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19070411-2214-0000-0000-00005F1ACA17 Message-Id: <8581b7e9-f09b-c273-ca8a-c83671cde919@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-07-04_06:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1907040149 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: linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Thursday 04 July 2019 04:43 PM, Michael Ellerman wrote: > "Naveen N. Rao" writes: >> Nathan Lynch wrote: >>> Aravinda Prasad writes: >>>> Calculating the maximum memory based on the number of lmbs >>>> and lmb size does not account for the RMA region. Hence >>>> use memory_hotplug_max(), which already accounts for the >>>> RMA region, to fetch the maximum memory value. Thanks to >>>> Nathan Lynch for suggesting the memory_hotplug_max() >>>> function. >>> >>> Well, I hope I haven't led you astray... will it give you the desired >>> result on a kernel configured without memory hotplug support, booted in >>> an LPAR with some huge pages configured? >>> >>> If so, then >>> Acked-by: Nathan Lynch >>> >>> It would likely help with review and future maintenance if the semantics >>> and intended use of the MaxMem field are made a little more >>> explicit. For example, is it supposed to include persistent memory? >>> Perhaps a follow-up patch could address this. Or maybe I'm overthinking >>> it. >> >> This was primarily aimed to replicate what AIX lparstat does and >> documentation (*) just says: >> >> Maximum Memory >> Maximum possible amount of Memory. >> >> I think this mirrors the maximum memory value set in the LPAR profile, >> and this provides a way to obtain that value from within the LPAR. > > But the doc string for memory_hotplug_max() says: > > * memory_hotplug_max - return max address of memory that may be added > > > ie. maximum *address* not maximum *amount*. > > Possibly it turns out to be the same value, but that is just because you > have no holes in your layout. > > So I don't think this patch is correct. memory_hotplug_max (in one of the cases) is taking the value from "ibm,lrdr-capacity" and according to PAPR: PAPR section C.6.3.1 ibm,lrdr-capacity: "The phys (of size #address-cells) communicates the maximum address in bytes and therefore, the most memory that can be allocated to this partition." On other cases memory_hotplug_max() is calculating based on the number of lmbs assigned to the partition, so should still give max mem value > > cheers > -- Regards, Aravinda