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Wed, 15 Jan 2020 01:07:54 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 00F14Xss147311; Wed, 15 Jan 2020 01:07:53 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3020.oracle.com with ESMTP id 2xh8et2m4e-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 15 Jan 2020 01:07:53 +0000 Received: from abhmp0016.oracle.com (abhmp0016.oracle.com [141.146.116.22]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 00F17qR2008866; Wed, 15 Jan 2020 01:07:52 GMT Received: from [192.168.1.206] (/71.63.128.209) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 14 Jan 2020 17:07:51 -0800 Subject: Re: [PATCH 2/2] mm/mempolicy: Skip walking HUGETLB vma if MPOL_MF_STRICT is specified alone To: Li Xinhai , "linux-mm@kvack.org" Cc: akpm , mhocko , "yang.shi" , n-horiguchi References: <1578993378-10860-1-git-send-email-lixinhai.lxh@gmail.com> <1578993378-10860-2-git-send-email-lixinhai.lxh@gmail.com> <2020011422092314671410@gmail.com> From: Mike Kravetz Message-ID: Date: Tue, 14 Jan 2020 17:07:50 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <2020011422092314671410@gmail.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=9500 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2001150008 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9500 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2001150008 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000004, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 1/14/20 6:09 AM, Li Xinhai wrote: > Add cc to > Yang Shi > Naoya Horiguchi > , who has been worked on this part > > On 2020-01-14 at 17:16 Li Xinhai wrote: >> Checking MPOL_MF_STRICT is ignored for HUGETLB vma according to mbind man >> page: >> >> Notes >> MPOL_MF_STRICT is ignored on huge page mappings. >> >> If MPOL_MF_STRICT is specified alone without any MOVE flag, we should >> indicate, from test_walk, that walking this vma should be skipped even if >> there are misplaced pages. >> >> Signed-off-by: Li Xinhai >> Cc: Michal Hocko >> Cc: Mike Kravetz I do not necessarily disagree with the change. However, this has made me question a couple things: 1) Why does the man page say MPOL_MF_STRICT is ignored on huge page mappings? - Is that leftover from the the days when huge page migration was not supported? - Is it just because huge page migration is more likely to fail than base page migration. 2) Does the mbind code function properly when unable to migrate a huge page MPOL_MF_STRICT is set? A quick look at the code looks like it returns EIO. I will look into these questions. However, if someone already knows the answer that would be appreciated. -- Mike Kravetz