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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 6 Mar 2019 12:45:53 -0000 Received: from b01ledav002.gho.pok.ibm.com (b01ledav002.gho.pok.ibm.com [9.57.199.107]) by b01cxnp22035.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x26CjqnR24641564 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 6 Mar 2019 12:45:52 GMT Received: from b01ledav002.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2DDDD124058; Wed, 6 Mar 2019 12:45:52 +0000 (GMT) Received: from b01ledav002.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 91B85124055; Wed, 6 Mar 2019 12:45:28 +0000 (GMT) Received: from [9.199.59.8] (unknown [9.199.59.8]) by b01ledav002.gho.pok.ibm.com (Postfix) with ESMTP; Wed, 6 Mar 2019 12:45:27 +0000 (GMT) Subject: Re: [PATCH 2/2] mm/dax: Don't enable huge dax mapping by default To: =?UTF-8?Q?Michal_Such=c3=a1nek?= Cc: Dan Williams , Oliver , Jan Kara , linux-nvdimm@lists.01.org, Linux Kernel Mailing List , Linux MM , Ross Zwisler , Andrew Morton , linuxppc-dev , "Kirill A . Shutemov" References: <20190228083522.8189-1-aneesh.kumar@linux.ibm.com> <20190228083522.8189-2-aneesh.kumar@linux.ibm.com> <87k1hc8iqa.fsf@linux.ibm.com> <20190306124453.126d36d8@naga.suse.cz> From: "Aneesh Kumar K.V" Date: Wed, 6 Mar 2019 18:15:25 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190306124453.126d36d8@naga.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19030612-0060-0000-0000-00000317A706 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010714; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000281; SDB=6.01170428; UDB=6.00611703; IPR=6.00951068; MB=3.00025857; MTD=3.00000008; XFM=3.00000015; UTC=2019-03-06 12:45:55 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19030612-0061-0000-0000-000048858CD3 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-03-06_08:,, 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=979 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903060087 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 3/6/19 5:14 PM, Michal Suchánek wrote: > On Wed, 06 Mar 2019 14:47:33 +0530 > "Aneesh Kumar K.V" wrote: > >> Dan Williams writes: >> >>> On Thu, Feb 28, 2019 at 1:40 AM Oliver wrote: >>>> >>>> On Thu, Feb 28, 2019 at 7:35 PM Aneesh Kumar K.V >>>> wrote: > >> Also even if the user decided to not use THP, by >> echo "never" > transparent_hugepage/enabled , we should continue to map >> dax fault using huge page on platforms that can support huge pages. > > Is this a good idea? > > This knob is there for a reason. In some situations having huge pages > can severely impact performance of the system (due to host-guest > interaction or whatever) and the ability to really turn off all THP > would be important in those cases, right? > My understanding was that is not true for dax pages? These are not regular memory that got allocated. They are allocated out of /dev/dax/ or /dev/pmem*. Do we have a reason not to use hugepages for mapping pages in that case? -aneesh