From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH] rdma: don't make pages writeable if not requiested Date: Thu, 21 Mar 2013 19:42:37 +0200 Message-ID: <20130321174237.GA4060@redhat.com> References: <20130321061838.GA28319@redhat.com> <20130321070357.GD28328@redhat.com> <20130321085107.GE28328@redhat.com> <20130321093946.GG28328@redhat.com> <20130321171115.GA653@obsidianresearch.com> <20130321171525.GE2994@redhat.com> <20130321172150.GA3118@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20130321172150.GA3118-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jason Gunthorpe Cc: Roland Dreier , "Michael R. Hines" , Sean Hefty , Hal Rosenstock , Yishai Hadas , Christoph Lameter , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , LKML , qemu-devel-qX2TKyscuCcdnm+yROfE0A@public.gmane.org List-Id: linux-rdma@vger.kernel.org On Thu, Mar 21, 2013 at 11:21:50AM -0600, Jason Gunthorpe wrote: > On Thu, Mar 21, 2013 at 07:15:25PM +0200, Michael S. Tsirkin wrote: > > > No because application does this: > > init page > > > > ... > > > > after a lot of time > > > > .. > > > > register > > send > > unregister > > > > so it can not be read only. > > mprotect(READONLY) > register > send > unregister > mprotect(WRITABLE) > > ? > With something like GIFT the app already has to give up writing to the > pages while they are moving, so changing the protection seems in line > with that? > > Jason It doesn't actually, and our app would sometimes write to these pages. It simply does not care which version does the remote get in this case since we track writes and resend later. Also this is per-page, MRs have byte granularity so easier to use. -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751722Ab3CURrX (ORCPT ); Thu, 21 Mar 2013 13:47:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:25778 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751103Ab3CURrV (ORCPT ); Thu, 21 Mar 2013 13:47:21 -0400 Date: Thu, 21 Mar 2013 19:42:37 +0200 From: "Michael S. Tsirkin" To: Jason Gunthorpe Cc: Roland Dreier , "Michael R. Hines" , Sean Hefty , Hal Rosenstock , Yishai Hadas , Christoph Lameter , "linux-rdma@vger.kernel.org" , LKML , qemu-devel@nongnu.org Subject: Re: [PATCH] rdma: don't make pages writeable if not requiested Message-ID: <20130321174237.GA4060@redhat.com> References: <20130321061838.GA28319@redhat.com> <20130321070357.GD28328@redhat.com> <20130321085107.GE28328@redhat.com> <20130321093946.GG28328@redhat.com> <20130321171115.GA653@obsidianresearch.com> <20130321171525.GE2994@redhat.com> <20130321172150.GA3118@obsidianresearch.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130321172150.GA3118@obsidianresearch.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 21, 2013 at 11:21:50AM -0600, Jason Gunthorpe wrote: > On Thu, Mar 21, 2013 at 07:15:25PM +0200, Michael S. Tsirkin wrote: > > > No because application does this: > > init page > > > > ... > > > > after a lot of time > > > > .. > > > > register > > send > > unregister > > > > so it can not be read only. > > mprotect(READONLY) > register > send > unregister > mprotect(WRITABLE) > > ? > With something like GIFT the app already has to give up writing to the > pages while they are moving, so changing the protection seems in line > with that? > > Jason It doesn't actually, and our app would sometimes write to these pages. It simply does not care which version does the remote get in this case since we track writes and resend later. Also this is per-page, MRs have byte granularity so easier to use. -- MST From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:47969) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIjaA-00021A-Fw for qemu-devel@nongnu.org; Thu, 21 Mar 2013 13:47:21 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UIja7-0003vH-Lg for qemu-devel@nongnu.org; Thu, 21 Mar 2013 13:47:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:15627) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIja7-0003v2-Cw for qemu-devel@nongnu.org; Thu, 21 Mar 2013 13:47:15 -0400 Date: Thu, 21 Mar 2013 19:42:37 +0200 From: "Michael S. Tsirkin" Message-ID: <20130321174237.GA4060@redhat.com> References: <20130321061838.GA28319@redhat.com> <20130321070357.GD28328@redhat.com> <20130321085107.GE28328@redhat.com> <20130321093946.GG28328@redhat.com> <20130321171115.GA653@obsidianresearch.com> <20130321171525.GE2994@redhat.com> <20130321172150.GA3118@obsidianresearch.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130321172150.GA3118@obsidianresearch.com> Subject: Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jason Gunthorpe Cc: Roland Dreier , qemu-devel@nongnu.org, "linux-rdma@vger.kernel.org" , Yishai Hadas , LKML , "Michael R. Hines" , Hal Rosenstock , Sean Hefty , Christoph Lameter On Thu, Mar 21, 2013 at 11:21:50AM -0600, Jason Gunthorpe wrote: > On Thu, Mar 21, 2013 at 07:15:25PM +0200, Michael S. Tsirkin wrote: > > > No because application does this: > > init page > > > > ... > > > > after a lot of time > > > > .. > > > > register > > send > > unregister > > > > so it can not be read only. > > mprotect(READONLY) > register > send > unregister > mprotect(WRITABLE) > > ? > With something like GIFT the app already has to give up writing to the > pages while they are moving, so changing the protection seems in line > with that? > > Jason It doesn't actually, and our app would sometimes write to these pages. It simply does not care which version does the remote get in this case since we track writes and resend later. Also this is per-page, MRs have byte granularity so easier to use. -- MST