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Mon, 27 Jul 2020 17:52:57 +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 06RHqMgT041167; Mon, 27 Jul 2020 17:52:56 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserp3020.oracle.com with ESMTP id 32hu5rb7x2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 27 Jul 2020 17:52:56 +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 06RHqpqA014090; Mon, 27 Jul 2020 17:52:52 GMT Received: from [192.168.2.112] (/50.38.35.18) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 27 Jul 2020 10:52:51 -0700 Subject: Re: [PATCH v3] mm/hugetlb: split hugetlb_cma in nodes with memory To: "Aneesh Kumar K.V" , Anshuman Khandual , Will Deacon , Roman Gushchin Cc: Barry Song , Catalin Marinas , x86@kernel.org, linux-kernel@vger.kernel.org, linuxarm@huawei.com, linux-mm@kvack.org, Ingo Molnar , Thomas Gleixner , Jonathan Cameron , "H.Peter Anvin" , Borislav Petkov , akpm@linux-foundation.org, Mike Rapoport , linux-arm-kernel@lists.infradead.org References: <20200710120950.37716-1-song.bao.hua@hisilicon.com> <359ea1d0-b1fd-d09f-d28a-a44655834277@oracle.com> <20200715081822.GA5683@willie-the-truck> <5724f1f8-63a6-ee0f-018c-06fb259b6290@oracle.com> <20200716081243.GA6561@willie-the-truck> <81103d30-f4fd-8807-03f9-d131da5097bd@arm.com> <1efdfe52-abdb-3931-742c-70e4a170e403@oracle.com> <11b03fcd-c210-032c-16d2-79ada41e0349@arm.com> <874kptm3b4.fsf@linux.ibm.com> From: Mike Kravetz Message-ID: <523426cd-1586-5d57-9650-134a2ac30d16@oracle.com> Date: Mon, 27 Jul 2020 10:52:49 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <874kptm3b4.fsf@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9695 signatures=668679 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 adultscore=0 bulkscore=0 malwarescore=0 mlxscore=0 spamscore=0 mlxlogscore=999 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007270120 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9695 signatures=668679 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 clxscore=1011 malwarescore=0 spamscore=0 suspectscore=0 bulkscore=0 priorityscore=1501 phishscore=0 mlxlogscore=999 lowpriorityscore=0 impostorscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007270120 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/27/20 7:37 AM, Aneesh Kumar K.V wrote: > There is variant of this which is pseries powerpc where there is > hypervisor assistance w.r.t allocating gigantic pages. See the ppc64 > enablement patch > > https://lore.kernel.org/linuxppc-dev/20200713150749.25245-1-aneesh.kumar@linux.ibm.com/ > Thanks Aneesh, I missed the powerpc support. I knew about the powerpc hypervisor assistance which caused me to rethink my original idea that all this could be arch independent. My next idea was that architectures would only need to provide a constant something like: #define HUGETLB_CMA_ORDER (PUD_SHIFT - PAGE_SHIFT) However, it looks like this can not be a compile time constant on powerpc. Moving more of the CMA support to arch independent code has moved down on my priority list. So, it it likely not to get much work in the immediate future. Just curious, can you have multiple gigantic page sizes supported at one time (one system instance) on powerpc? -- Mike Kravetz