From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 12 Feb 2008 16:56:45 -0800 (PST) From: Christoph Lameter Subject: Re: [ofa-general] Re: Demand paging for memory regions In-Reply-To: Message-ID: References: <20080208234302.GH26564@sgi.com> <20080208155641.2258ad2c.akpm@linux-foundation.org> <20080209012446.GB7051@v2.random> <20080209015659.GC7051@v2.random> <20080209075556.63062452@bree.surriel.com> <47B2174E.5000708@opengridcomputing.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Roland Dreier Cc: Steve Wise , Rik van Riel , Andrea Arcangeli , a.p.zijlstra@chello.nl, izike@qumranet.com, steiner@sgi.com, linux-kernel@vger.kernel.org, avi@qumranet.com, linux-mm@kvack.org, daniel.blueman@quadrics.com, Robin Holt , general@lists.openfabrics.org, Andrew Morton , kvm-devel@lists.sourceforge.net List-ID: On Tue, 12 Feb 2008, Roland Dreier wrote: > I don't know anything about the T3 internals, but it's not clear that > you could do this without a new chip design in general. Lot's of RDMA > devices were designed expecting that when a packet arrives, the HW can > look up the bus address for a given memory region/offset and place the > packet immediately. It seems like a major change to be able to > generate a "page fault" interrupt when a page isn't present, or even > just wait to scatter some data until the host finishes updating page > tables when the HW needs the translation. Well if the VM wants to invalidate a page then the remote end first has to remove its mapping. If a page has been removed then the remote end would encounter a fault and then would have to wait for the local end to reestablish its mapping before proceeding. So the packet would only be generated when both ends are in sync. -- 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