From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id B173F6B038D for ; Wed, 15 Mar 2017 12:59:36 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id e129so40570445pfh.1 for ; Wed, 15 Mar 2017 09:59:36 -0700 (PDT) Date: Wed, 15 Mar 2017 09:57:36 -0700 From: Matthew Wilcox Subject: Re: [RFC PATCH 00/13] Introduce first class virtual address spaces Message-ID: <20170315165736.GE4033@bombadil.infradead.org> References: <20170314161229.tl6hsmian2gdep47@arch-dev> 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: Andy Lutomirski Cc: Andy Lutomirski , Till Smejkal , Richard Henderson , Ivan Kokshaysky , Matt Turner , Vineet Gupta , Russell King , Catalin Marinas , Will Deacon , Steven Miao , Richard Kuo , Tony Luck , Fenghua Yu , James Hogan , Ralf Baechle , "James E.J. Bottomley" , Helge Deller , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Martin Schwidefsky , Heiko Carstens , Yoshinori Sato , Rich Felker , "David S. Miller" , Chris Metcalf , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , X86 ML , Chris Zankel , Max Filippov , Arnd Bergmann , Greg Kroah-Hartman , Laurent Pinchart , Mauro Carvalho Chehab , Pawel Osciak , Marek Szyprowski , Kyungmin Park , David Woodhouse , Brian Norris , Boris Brezillon , Marek Vasut , Richard Weinberger , Cyrille Pitchen , Felipe Balbi , Alexander Viro , Benjamin LaHaise , Nadia Yvette Chambers , Jeff Layton , "J. Bruce Fields" , Peter Zijlstra , Hugh Dickins , Arnaldo Carvalho de Melo , Alexander Shishkin , Jaroslav Kysela , Takashi Iwai , "linux-kernel@vger.kernel.org" , linux-alpha@vger.kernel.org, arcml , "linux-arm-kernel@lists.infradead.org" , adi-buildroot-devel@lists.sourceforge.net, linux-hexagon@vger.kernel.org, "linux-ia64@vger.kernel.org" , linux-metag@vger.kernel.org, Linux MIPS Mailing List , linux-parisc@vger.kernel.org, linuxppc-dev , "linux-s390@vger.kernel.org" , "linux-sh@vger.kernel.org" , sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, Linux Media Mailing List , linux-mtd@lists.infradead.org, USB list , Linux FS Devel , linux-aio@kvack.org, "linux-mm@kvack.org" , Linux API , linux-arch , ALSA development On Wed, Mar 15, 2017 at 09:51:31AM -0700, Andy Lutomirski wrote: > > VAS segments on the other side allow sharing of pure in memory data by > > arbitrary related tasks without the need of a file. This becomes especially > > interesting if one combines VAS segments with non-volatile memory since one can keep > > data structures in the NVM and still be able to share them between multiple tasks. > > What's wrong with regular mmap? I think it's the usual misunderstandings about how to use mmap. >>From the paper: Memory-centric computing demands careful organization of the virtual address space, but interfaces such as mmap only give limited control. Some systems do not support creation of address regions at specific offsets. In Linux, for example, mmap does not safely abort if a request is made to open a region of memory over an existing region; it simply writes over it. The correct answer of course, is "Don't specify MAP_FIXED". Specify the 'hint' address, and if you don't get it, either fix up your data structure pointers, or just abort and complain noisily. -- 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