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dkim=none (message not signed) header.d=none;vger.kernel.org; dmarc=none action=none header.from=oracle.com; Received: from BY5PR10MB4196.namprd10.prod.outlook.com (2603:10b6:a03:20d::23) by BY5PR10MB4115.namprd10.prod.outlook.com (2603:10b6:a03:213::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3977.26; Wed, 14 Apr 2021 17:03:45 +0000 Received: from BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::980e:61ba:57d2:47ee]) by BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::980e:61ba:57d2:47ee%7]) with mapi id 15.20.4042.016; Wed, 14 Apr 2021 17:03:45 +0000 Subject: Re: [PATCH v7 4/7] mm,hugetlb: Split prep_new_huge_page functionality To: Oscar Salvador Cc: Andrew Morton , Vlastimil Babka , David Hildenbrand , Michal Hocko , Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210413104747.12177-1-osalvador@suse.de> <20210413104747.12177-5-osalvador@suse.de> <94992151-03fc-dedd-3e09-811908d26d04@oracle.com> From: Mike Kravetz Message-ID: Date: Wed, 14 Apr 2021 10:03:43 -0700 User-Agent: Mozilla/5.0 (X11; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: da05b6a3-384a-4c40-ba27-08d8ff6743c1 X-MS-Exchange-CrossTenant-AuthSource: BY5PR10MB4196.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Apr 2021 17:03:45.8121 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 40Kp5tsZUXLNe306S3T2bl/wjoLk0eN3tUyiWp5OzeqGtZSHazzNnRqnuaYVL/ym/tXCD9qzavdzKWpKKRmTRg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR10MB4115 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9954 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 adultscore=0 malwarescore=0 suspectscore=0 bulkscore=0 mlxscore=0 spamscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104140110 X-Proofpoint-ORIG-GUID: oUswibFRRiiqyGdDjUUmyf1N2rB0DnW0 X-Proofpoint-GUID: oUswibFRRiiqyGdDjUUmyf1N2rB0DnW0 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9954 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 clxscore=1015 adultscore=0 mlxlogscore=999 bulkscore=0 malwarescore=0 spamscore=0 impostorscore=0 suspectscore=0 mlxscore=0 phishscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104140111 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/13/21 9:59 PM, Oscar Salvador wrote: > On Tue, Apr 13, 2021 at 02:33:41PM -0700, Mike Kravetz wrote: >>> -static void prep_new_huge_page(struct hstate *h, struct page *page, int nid) >>> +/* >>> + * Must be called with the hugetlb lock held >>> + */ >>> +static void __prep_account_new_huge_page(struct hstate *h, int nid) >>> +{ >>> + h->nr_huge_pages++; >>> + h->nr_huge_pages_node[nid]++; >> >> I would prefer if we also move setting the destructor to this routine. >> set_compound_page_dtor(page, HUGETLB_PAGE_DTOR); > > Uhm, but that is the routine that does the accounting, it feels wrong > here, plus... > >> >> That way, PageHuge() will be false until it 'really' is a huge page. >> If not, we could potentially go into that retry loop in >> dissolve_free_huge_page or alloc_and_dissolve_huge_page in patch 5. > > ...I do not follow here, could you please elaborate some more? > Unless I am missing something, behaviour should not be any different with this > patch. > I was thinking of the time between the call to __prep_new_huge_page and __prep_account_new_huge_page. In that time, PageHuge() will be true but the page is not yet fully being managed as a hugetlb page. My thought was that isolation, migration, offline or any code that does pfn scanning might the page as PageHuge() (after taking lock) and start to process it. Now I see that in patch 5 you call both __prep_new_huge_page and __prep_account_new_huge_page with the lock held. So, no issue. Sorry. I 'think' there may still be a potential race with the prep_new_huge_page routine, but that existed before any of your changes. It may also be that 'synchronization' at the pageblock level which prevents some of these pfn scanning operations to operate on the same pageblocks may prevent this from ever happening. Mostly thinking out loud. Upon further thought, I have no objections to this change. Sorry for the noise. Reviewed-by: Mike Kravetz -- Mike Kravetz