From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id 08DA16B0033 for ; Fri, 13 Oct 2017 11:47:52 -0400 (EDT) Received: by mail-wr0-f197.google.com with SMTP id k15so830961wrc.1 for ; Fri, 13 Oct 2017 08:47:51 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id b191si1127456wma.214.2017.10.13.08.47.50 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 13 Oct 2017 08:47:50 -0700 (PDT) Date: Fri, 13 Oct 2017 17:47:47 +0200 From: Michal Hocko Subject: Re: [RFC PATCH 3/3] mm/map_contig: Add mmap(MAP_CONTIG) support Message-ID: <20171013154747.2jv7rtfqyyagiodn@dhcp22.suse.cz> References: <21f1ec96-2822-1189-1c95-79a2bb491571@oracle.com> <20171012014611.18725-1-mike.kravetz@oracle.com> <20171012014611.18725-4-mike.kravetz@oracle.com> <20171012143756.p5bv4zx476qkmqhh@dhcp22.suse.cz> <20171013084054.me3kxhgbxzgm2lpr@dhcp22.suse.cz> <20171013152801.nbpk6nluotgbmfrs@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Christopher Lameter Cc: Mike Kravetz , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Marek Szyprowski , Michal Nazarewicz , "Aneesh Kumar K . V" , Joonsoo Kim , Guy Shattah , Anshuman Khandual , Laura Abbott , Vlastimil Babka On Fri 13-10-17 10:42:37, Cristopher Lameter wrote: > On Fri, 13 Oct 2017, Michal Hocko wrote: > > > On Fri 13-10-17 10:20:06, Cristopher Lameter wrote: > > > On Fri, 13 Oct 2017, Michal Hocko wrote: > > [...] > > > > I am not really convinced this is a good interface. You are basically > > > > trying to bypass virtual memory abstraction and that is quite > > > > contradicting the mmap API to me. > > > > > > This is a standardized posix interface as described in our presentation at > > > the plumbers conference. See the presentation on contiguous allocations. > > > > Are you trying to desing a generic interface with a very specific and HW > > dependent usecase in mind? > > There is a generic posix interface that could we used for a variety of > specific hardware dependent use cases. Yes you wrote that already and my counter argument was that this generic posix interface shouldn't bypass virtual memory abstraction. > > > The contiguous allocations are particularly useful for the RDMA API which > > > allows registering user space memory with devices. > > > > then make those devices expose an implementation of an mmap which does > > that. You would get both a proper access control (via fd), accounting > > and others. > > There are numerous RDMA devices that would all need the mmap > implementation. And this covers only the needs of one subsystem. There are > other use cases. That doesn't prevent providing a library function which could be reused by all those drivers. Nothing really too much different from remap_pfn_range. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org