From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Tue, 14 Mar 2017 02:31:27 +0100 (CET) Received: from mail-wm0-x242.google.com ([IPv6:2a00:1450:400c:c09::242]:34937 "EHLO mail-wm0-x242.google.com" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S23994766AbdCNBbVYxbNb (ORCPT ); Tue, 14 Mar 2017 02:31:21 +0100 Received: by mail-wm0-x242.google.com with SMTP id z63so12548684wmg.2; Mon, 13 Mar 2017 18:31:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=20161025; h=from:date:to:cc:subject:message-id:mail-followup-to:mime-version :content-disposition:in-reply-to:user-agent; bh=RcdCplRFEgF8BLITwxt5zck0mddUo9r+/XC3gPtPx5E=; b=EgoObGd55uxIE6SRqECTGJxopY0qiIUVT363P/4nOd6SOLpTQ9Ux1VhKzUIMKPyfLp rkIHWUZJVn2R7D5VnNwrtH11sg0WQGKGR2Wnt5cjxYiE2pwuSDaW96y/w8CZRlQVadb8 kOVTrVpDLGGmWIqUXyV7Jtn0F8RT93q6YcCwIQx5+WTJx6EnfDhdmo8bIbuMIbinhTdU wuKxeWrFB5PHA5GaKXjPOuM/b/4oFlLEX8tCEIgkR7+kXcQTBeMlz6O8cQi64LHnvYnP ydDMXIDkVuKGO/niC3rcCP44rCAje8FlzxNRDV3OV4ABH9d5eLbLE7+is9VC9tiFZ7wV uVxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id :mail-followup-to:mime-version:content-disposition:in-reply-to :user-agent; bh=RcdCplRFEgF8BLITwxt5zck0mddUo9r+/XC3gPtPx5E=; b=M9AQ4mmv6MJWifApKXBQ0JVcIQFxzmZXtkOXUNKIua+1X7yc2kY4pBDr6eowx6QA5T vMv0tIgSJoXK1ugeLPS9Sw4p0YeCXG645PUleaqhFuA3w/R+Meq7OSkj+WI2MLoa8GRQ 1oi+sPbyDUUpY5N+ixsjahbaDU21vuMmxR734qMT26Oswt1g172rxyf93yZc5Xaxkj4W gX+RzfpuEHMi4/v06L9GUETjDvzi6iuduF6k7pUPIaAJ9AYD0qB/B8SRYepkRCjBRZJB 72L8LS2HOdbXVnoixIAzcPfosztwb3bOCnq+yA38UTbMo9zHMzFZhAWI7rxsYQMsdWW3 3FjQ== X-Gm-Message-State: AFeK/H3sKFGZvEGCix51QjWeqI8zPHJNw54dWP1TssMxSI92WeDU6NNfOUKkpXmPDc0sMA== X-Received: by 10.28.151.142 with SMTP id z136mr13847406wmd.20.1489455076097; Mon, 13 Mar 2017 18:31:16 -0700 (PDT) Received: from localhost (login1.zih.tu-dresden.de. [141.76.16.140]) by smtp.googlemail.com with ESMTPSA id 32sm26904219wrr.64.2017.03.13.18.31.14 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 13 Mar 2017 18:31:14 -0700 (PDT) From: Till Smejkal X-Google-Original-From: Till Smejkal Date: Mon, 13 Mar 2017 18:31:12 -0700 To: Richard Henderson Cc: Till Smejkal , 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@kernel.org, Andy Lutomirski , 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, linux-snps-arc@lists.infradead.org, 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@linux-mips.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-media@vger.kernel.org, linux-mtd@lists.infradead.org, linux-usb@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, linux-mm@kvack.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, alsa-devel@alsa-project.org Subject: Re: [RFC PATCH 00/13] Introduce first class virtual address spaces Message-ID: <20170314013112.ofhcgg2stzoft5mw@arch-dev> Mail-Followup-To: Richard Henderson , Till Smejkal , 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@kernel.org, Andy Lutomirski , 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, linux-snps-arc@lists.infradead.org, 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@linux-mips.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-media@vger.kernel.org, linux-mtd@lists.infradead.org, linux-usb@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, linux-mm@kvack.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, alsa-devel@alsa-project.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170306 (1.8.0) Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 57191 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: till.smejkal@googlemail.com Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips On Tue, 14 Mar 2017, Richard Henderson wrote: > On 03/14/2017 10:39 AM, Till Smejkal wrote: > > > Is this an indication that full virtual address spaces are useless? It > > > would seem like if you only use virtual address segments then you avoid all > > > of the problems with executing code, active stacks, and brk. > > > > What do you mean with *virtual address segments*? The nice part of first class > > virtual address spaces is that one can share/reuse collections of address space > > segments easily. > > What do *I* mean? You introduced the term, didn't you? > Rereading your original I see you called them "VAS segments". Oh, I am sorry. I thought that you were referring to some other feature that I don't know. > Anyway, whatever they are called, it would seem that these segments do not > require any of the syncing mechanisms that are causing you problems. Yes, VAS segments provide a possibility to share memory regions between multiple address spaces without the need to synchronize heap, stack, etc. Unfortunately, the VAS segment feature itself without the whole concept of first class virtual address spaces is not as powerful. With some additional work it can probably be represented with the existing shmem functionality. The first class virtual address space feature on the other side provides a real benefit for applications in our opinion namely that an application can switch between different views on its memory which enables various interesting programming paradigms as mentioned in the cover letter. Till