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dkim=none (message not signed) header.d=none;infradead.org; dmarc=none action=none header.from=oracle.com; Received: from BYAPR10MB3077.namprd10.prod.outlook.com (2603:10b6:a03:8c::12) by BYAPR10MB2552.namprd10.prod.outlook.com (2603:10b6:a02:ad::23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3825.17; Thu, 11 Feb 2021 10:45:09 +0000 Received: from BYAPR10MB3077.namprd10.prod.outlook.com ([fe80::74a8:8649:e20b:d571]) by BYAPR10MB3077.namprd10.prod.outlook.com ([fe80::74a8:8649:e20b:d571%7]) with mapi id 15.20.3825.030; Thu, 11 Feb 2021 10:45:09 +0000 Subject: Re: [PATCH v3 1/4] mm/gup: add compound page list iterator To: Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, Andrew Morton , Doug Ledford , John Hubbard , Matthew Wilcox References: <20210205204127.29441-1-joao.m.martins@oracle.com> <20210205204127.29441-2-joao.m.martins@oracle.com> <20210210232010.GT4718@ziepe.ca> From: Joao Martins Message-ID: <87b7f24d-0065-9f55-5c96-e7853b2e8068@oracle.com> Date: Thu, 11 Feb 2021 10:45:02 +0000 In-Reply-To: <20210210232010.GT4718@ziepe.ca> Content-Type: text/plain; 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It >> essentially counts the tails until the next page to process has a >> different head that the current. This is going to be used by >> unpin_user_pages() family of functions, to batch the head page refcount >> updates once for all passed consecutive tail pages. >> >> Suggested-by: Jason Gunthorpe >> Signed-off-by: Joao Martins >> Reviewed-by: John Hubbard >> --- >> mm/gup.c | 26 ++++++++++++++++++++++++++ >> 1 file changed, 26 insertions(+) > > Reviewed-by: Jason Gunthorpe > Thanks! > This can be used for check_and_migrate_cma_pages() too (there is a > series around to change this logic though, not sure if it is landed > yet) It got unqueued AFAIUI. It makes sense for most users today except hugetlb pages, which are also the fastest page pinner today. And unilaterally using this iterator makes all page types pay the added cost. So either keeping the current loop having the exception to PageHuge() head pages, or doing it correctly with that split logic we were talking on the other thread. Joao