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Fri, 12 Jun 2020 03:29:37 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 05C3MtIB154197; Fri, 12 Jun 2020 03:29:37 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserp3020.oracle.com with ESMTP id 31m1rhgnke-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 12 Jun 2020 03:29:36 +0000 Received: from abhmp0015.oracle.com (abhmp0015.oracle.com [141.146.116.21]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 05C3TYtc008852; Fri, 12 Jun 2020 03:29:34 GMT Received: from ca-dmjordan1.us.oracle.com (/10.211.9.48) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 11 Jun 2020 20:29:33 -0700 Date: Thu, 11 Jun 2020 23:29:59 -0400 From: Daniel Jordan To: Dave Hansen Cc: Daniel Jordan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Andy Lutomirski , Dave Hansen , David Hildenbrand , Michal Hocko , Pavel Tatashin , Peter Zijlstra , Steven Sistare Subject: Re: [PATCH v2] x86/mm: use max memory block size on bare metal Message-ID: <20200612032959.yo43ydg273zu35lx@ca-dmjordan1.us.oracle.com> References: <20200609225451.3542648-1-daniel.m.jordan@oracle.com> <20200611165910.6dwd3c7z5brimjbm@ca-dmjordan1.us.oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9649 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 adultscore=0 bulkscore=0 malwarescore=0 mlxlogscore=999 spamscore=0 suspectscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006120025 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9649 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 impostorscore=0 cotscore=-2147483648 priorityscore=1501 spamscore=0 suspectscore=0 lowpriorityscore=0 bulkscore=0 mlxlogscore=999 malwarescore=0 mlxscore=0 phishscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006120025 X-Rspamd-Queue-Id: 31C12180AD82F 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 Thu, Jun 11, 2020 at 10:05:38AM -0700, Dave Hansen wrote: > One other nit for this. We *do* have actual hardware hotplug, and I'm > pretty sure the alignment guarantees for hardware hotplug are pretty > weak. For instance, the alignment guarantees for persistent memory are > still only 64MB even on modern platforms. > > Let's say we're on bare metal and we see an SRAT table that has some > areas that show that hotplug might happen there. Is this patch still > ideal there? Well, not if there's concern about hardware hotplug. My assumption going in was that this wasn't a problem in practice. 078eb6aa50dc50 ("x86/mm/memory_hotplug: determine block size based on the end of boot memory") was merged in 2018 to address qemu hotplug failures and >64G systems have used a 2G block since 2014 with no complaints about alignment issues, to my knowledge anyway.