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Thu, 09 Apr 2020 22:08:10 +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 039M6umD116523; Thu, 9 Apr 2020 22:08:09 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3030.oracle.com with ESMTP id 309ag5tgdw-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 09 Apr 2020 22:08:09 +0000 Received: from abhmp0001.oracle.com (abhmp0001.oracle.com [141.146.116.7]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 039M88EO014851; Thu, 9 Apr 2020 22:08:08 GMT Received: from [192.168.1.206] (/71.63.128.209) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 09 Apr 2020 15:08:08 -0700 Subject: Re: [PATCH] Documentation: hugetlb: Update hugetlb options To: Peter Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Nitesh Narayan Lal , Andrew Morton References: <20200409215800.8967-1-peterx@redhat.com> From: Mike Kravetz Message-ID: Date: Thu, 9 Apr 2020 15:08:07 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200409215800.8967-1-peterx@redhat.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=9586 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 spamscore=0 malwarescore=0 phishscore=0 mlxscore=0 bulkscore=0 mlxlogscore=999 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004090156 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9586 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 bulkscore=0 phishscore=0 lowpriorityscore=0 impostorscore=0 clxscore=1011 suspectscore=0 malwarescore=0 spamscore=0 mlxlogscore=999 mlxscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004090155 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 4/9/20 2:58 PM, Peter Xu wrote: > The hugepage options are not documented clearly. > > Firstly, default_hugepagesz= should always be specified after the > declaration of the same type of huge page using hugepagesz=. For > example, if we boot a x86_64 system with kernel cmdline > "default_hugepagesz=2M", we'll get a very funny error message: > > "HugeTLB: unsupported default_hugepagesz 2097152. Reverting to 2097152" > > It's understandable from code-wise because when hugetlb_init() we > didn't have the 2M page hstate registered, so it's unsupported. > However 2M is actually the default huge page size on x86_64, so we'll > register it right after the error message. However it's very > confusing if without these knowledges. > > Secondly, hugepages= option must be used _after_ another hugepagesz=. > The word "interleave" is fine but it didn't declare the fact that > each of the hugepages= option will be applied to the previous parsed > hugepagesz= option. > > State all these clear. > > Signed-off-by: Peter Xu Hi Peter, Did you happen to see this patch series? https://lore.kernel.org/linux-mm/20200401183819.20647-1-mike.kravetz@oracle.com/ That should address the documentation issue and more. -- Mike Kravetz