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Tue, 10 Mar 2020 17:38:32 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 02AHYG5t112155; Tue, 10 Mar 2020 17:38:31 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserp3030.oracle.com with ESMTP id 2yp8psry8k-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 10 Mar 2020 17:38:31 +0000 Received: from abhmp0004.oracle.com (abhmp0004.oracle.com [141.146.116.10]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 02AHcQAS030678; Tue, 10 Mar 2020 17:38:26 GMT Received: from [192.168.1.206] (/71.63.128.209) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 10 Mar 2020 10:38:26 -0700 Subject: Re: [PATCH v2] mm: hugetlb: optionally allocate gigantic hugepages using cma To: Michal Hocko , Roman Gushchin Cc: Andrew Morton , Johannes Weiner , linux-mm@kvack.org, kernel-team@fb.com, linux-kernel@vger.kernel.org, Rik van Riel References: <20200310002524.2291595-1-guro@fb.com> <20200310084544.GY8447@dhcp22.suse.cz> From: Mike Kravetz Message-ID: Date: Tue, 10 Mar 2020 10:38:24 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200310084544.GY8447@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9556 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 malwarescore=0 mlxlogscore=999 bulkscore=0 suspectscore=0 mlxscore=0 spamscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003100106 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9556 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 lowpriorityscore=0 spamscore=0 priorityscore=1501 impostorscore=0 bulkscore=0 suspectscore=0 phishscore=0 mlxlogscore=999 mlxscore=0 malwarescore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003100106 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 3/10/20 1:45 AM, Michal Hocko wrote: > On Mon 09-03-20 17:25:24, Roman Gushchin wrote: >> +early_param("hugetlb_cma", cmdline_parse_hugetlb_cma); >> + >> +void __init hugetlb_cma_reserve(void) >> +{ >> + unsigned long totalpages = 0; >> + unsigned long start_pfn, end_pfn; >> + phys_addr_t size; >> + int nid, i, res; >> + >> + if (!hugetlb_cma_size && !hugetlb_cma_percent) >> + return; >> + >> + if (hugetlb_cma_percent) { >> + for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, >> + NULL) >> + totalpages += end_pfn - start_pfn; >> + >> + size = PAGE_SIZE * (hugetlb_cma_percent * 100 * totalpages) / >> + 10000UL; >> + } else { >> + size = hugetlb_cma_size; >> + } >> + >> + pr_info("hugetlb_cma: reserve %llu, %llu per node\n", size, >> + size / nr_online_nodes); >> + >> + size /= nr_online_nodes; >> + >> + for_each_node_state(nid, N_ONLINE) { >> + unsigned long min_pfn = 0, max_pfn = 0; >> + >> + for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) { >> + if (!min_pfn) >> + min_pfn = start_pfn; >> + max_pfn = end_pfn; >> + } > > Do you want to compare the range to the size? But besides that, I > believe this really needs to be much more careful. I believe you do not > want to eat a considerable part of the kernel memory because the > resulting configuration will really struggle (yeah all the low mem/high > mem problems all over again). Will it struggle any worse than if the we allocated the same amount of memory for gigantic pages as is done today? Of course, sys admins may think reserving memory for CMA is better than pre-allocating and end up reserving a greater amount. -- Mike Kravetz