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dkim=none (message not signed) header.d=none;bytedance.com; dmarc=none action=none header.from=oracle.com; Received: from BY5PR10MB4196.namprd10.prod.outlook.com (2603:10b6:a03:20d::23) by SJ0PR10MB4462.namprd10.prod.outlook.com (2603:10b6:a03:2d7::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4129.26; Wed, 19 May 2021 22:44:52 +0000 Received: from BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::4407:2ff6:c0a:5d90]) by BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::4407:2ff6:c0a:5d90%8]) with mapi id 15.20.4129.033; Wed, 19 May 2021 22:44:52 +0000 Subject: Re: [External] Re: [PATCH] arm64: mm: hugetlb: add support for free vmemmap pages of HugeTLB To: Muchun Song , Anshuman Khandual Cc: Will Deacon , Andrew Morton , David Hildenbrand , "Bodeddula, Balasubramaniam" , Oscar Salvador , David Rientjes , linux-arm-kernel@lists.infradead.org, LKML , Linux Memory Management List , Xiongchun duan , fam.zheng@bytedance.com, zhengqi.arch@bytedance.com References: <20210518091826.36937-1-songmuchun@bytedance.com> <5ae7a4be-dfd5-faf6-a75c-a2adf5a344b2@arm.com> From: Mike Kravetz Message-ID: <7c39926f-3e8c-afda-7a68-81d2a65c580c@oracle.com> Date: Wed, 19 May 2021 15:44:50 -0700 User-Agent: Mozilla/5.0 (X11; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 5/19/21 9:21 AM, Muchun Song wrote: > On Wed, May 19, 2021 at 11:22 PM Muchun Song wrote: >> >> On Wed, May 19, 2021 at 10:43 PM Muchun Song wrote: >>> >>> On Wed, May 19, 2021 at 8:35 PM Anshuman Khandual >>> wrote: >>>> How does this interact with HugeTLB migration as such which might iterate >>>> over individual constituent struct pages (overriding the same struct page >>>> for all tail pages when this feature is enabled). A simple test involving >>>> madvise(ptr, size, MADV_SOFT_OFFLINE) fails on various HugeTLB page sizes, >>>> with this patch applied. Although I have not debugged this any further. >>> >>> It is weird. Actually, I didn't change the behaviour of the page migration. >>> This feature is default off. If you want to enable this feature, you can pass >>> "hugetlb_free_vmemmap=on" to the boot cmdline. Do you mean that the >>> success rate of page migration will decrease when you enable this feature? >>> The rate will increase if disbale. Right? >> >> I have done the test and found the issue. Because unmap_and_move_huge_page >> always returns -EBUSY. I will look into this issue in depth. Thanks for your >> report. >> >> The return point is as below: >> >> if (page_private(hpage) && !page_mapping(hpage)) { >> rc = -EBUSY; >> goto out_unlock; >> } > > I know the issue. It was caused by commit d6995da31122 ("hugetlb: > use page.private for hugetlb specific page flags"). The below patch > can fix this issue. > > diff --git a/mm/migrate.c b/mm/migrate.c > index e7a173da74ec..43419c4bb097 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1290,7 +1290,7 @@ static int unmap_and_move_huge_page(new_page_t > get_new_page, > * page_mapping() set, hugetlbfs specific move page routine will not > * be called and we could leak usage counts for subpools. > */ > - if (page_private(hpage) && !page_mapping(hpage)) { > + if (hugetlb_page_subpool(hpage) && !page_mapping(hpage)) { > rc = -EBUSY; > goto out_unlock; > } > Thank you Muchun! That was my bad commit. -- Mike Kravetz _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel