From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx203.postini.com [74.125.245.203]) by kanga.kvack.org (Postfix) with SMTP id C53866B0005 for ; Wed, 10 Apr 2013 23:37:43 -0400 (EDT) Received: by mail-qe0-f41.google.com with SMTP id b10so675933qen.0 for ; Wed, 10 Apr 2013 20:37:42 -0700 (PDT) Message-ID: <51662FFF.10103@gmail.com> Date: Thu, 11 Apr 2013 11:37:35 +0800 From: Simon Jeons MIME-Version: 1.0 Subject: Re: [LSF/MM TOPIC] Hardware initiated paging of user process pages, hardware access to the CPU page tables of user processes References: <5114DF05.7070702@mellanox.com> <5164C6EE.7020502@gmail.com> <20130410205557.GB3958@gmail.com> In-Reply-To: <20130410205557.GB3958@gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Jerome Glisse Cc: Michel Lespinasse , Shachar Raindel , lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, Andrea Arcangeli , Roland Dreier , Haggai Eran , Or Gerlitz , Sagi Grimberg , Liran Liss Hi Jerome, On 04/11/2013 04:55 AM, Jerome Glisse wrote: > On Wed, Apr 10, 2013 at 09:57:02AM +0800, Simon Jeons wrote: >> Hi Jerome, >> On 02/10/2013 12:29 AM, Jerome Glisse wrote: >>> On Sat, Feb 9, 2013 at 1:05 AM, Michel Lespinasse wrote: >>>> On Fri, Feb 8, 2013 at 3:18 AM, Shachar Raindel wrote: >>>>> Hi, >>>>> >>>>> We would like to present a reference implementation for safely sharing >>>>> memory pages from user space with the hardware, without pinning. >>>>> >>>>> We will be happy to hear the community feedback on our prototype >>>>> implementation, and suggestions for future improvements. >>>>> >>>>> We would also like to discuss adding features to the core MM subsystem to >>>>> assist hardware access to user memory without pinning. >>>> This sounds kinda scary TBH; however I do understand the need for such >>>> technology. >>>> >>>> I think one issue is that many MM developers are insufficiently aware >>>> of such developments; having a technology presentation would probably >>>> help there; but traditionally LSF/MM sessions are more interactive >>>> between developers who are already quite familiar with the technology. >>>> I think it would help if you could send in advance a detailed >>>> presentation of the problem and the proposed solutions (and then what >>>> they require of the MM layer) so people can be better prepared. >>>> >>>> And first I'd like to ask, aren't IOMMUs supposed to already largely >>>> solve this problem ? (probably a dumb question, but that just tells >>>> you how much you need to explain :) >>> For GPU the motivation is three fold. With the advance of GPU compute >>> and also with newer graphic program we see a massive increase in GPU >>> memory consumption. We easily can reach buffer that are bigger than >>> 1gbytes. So the first motivation is to directly use the memory the >>> user allocated through malloc in the GPU this avoid copying 1gbytes of >>> data with the cpu to the gpu buffer. The second and mostly important >>> to GPU compute is the use of GPU seamlessly with the CPU, in order to >>> achieve this you want the programmer to have a single address space on >>> the CPU and GPU. So that the same address point to the same object on >>> GPU as on the CPU. This would also be a tremendous cleaner design from >>> driver point of view toward memory management. >> When GPU will comsume memory? >> >> The userspace process like mplayer will have video datas and GPU >> will play this datas and use memory of mplayer since these video >> datas load in mplayer process's address space? So GPU codes will >> call gup to take a reference of memory? Please correct me if my >> understanding is wrong. ;-) > First target is not thing such as video decompression, however they could > too benefit from it given updated driver kernel API. In case of using > iommu hardware page fault we don't call get_user_pages (gup) those we > don't take a reference on the page. That's the whole point of the hardware > pagefault, not taking reference on the page. mplayer process is running on normal CPU or GPU? chipset_integrated graphics will use normal memory and discrete graphics will use its own memory, correct? So the memory used by discrete graphics won't need gup, correct? > > Cheers, > Jerome Glisse -- 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