From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 8 Feb 2008 14:23:15 -0800 From: Andrew Morton Subject: Re: [patch 0/6] MMU Notifiers V6 Message-Id: <20080208142315.7fe4b95e.akpm@linux-foundation.org> In-Reply-To: <20080208220616.089936205@sgi.com> References: <20080208220616.089936205@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: andrea@qumranet.com, holt@sgi.com, avi@qumranet.com, izike@qumranet.com, kvm-devel@lists.sourceforge.net, a.p.zijlstra@chello.nl, steiner@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, daniel.blueman@quadrics.com, general@lists.openfabrics.org List-ID: On Fri, 08 Feb 2008 14:06:16 -0800 Christoph Lameter wrote: > This is a patchset implementing MMU notifier callbacks based on Andrea's > earlier work. These are needed if Linux pages are referenced from something > else than tracked by the rmaps of the kernel (an external MMU). MMU > notifiers allow us to get rid of the page pinning for RDMA and various > other purposes. It gets rid of the broken use of mlock for page pinning. > (mlock really does *not* pin pages....) > > More information on the rationale and the technical details can be found in > the first patch and the README provided by that patch in > Documentation/mmu_notifiers. > > The known immediate users are > > KVM > - Establishes a refcount to the page via get_user_pages(). > - External references are called spte. > - Has page tables to track pages whose refcount was elevated but > no reverse maps. > > GRU > - Simple additional hardware TLB (possibly covering multiple instances of > Linux) > - Needs TLB shootdown when the VM unmaps pages. > - Determines page address via follow_page (from interrupt context) but can > fall back to get_user_pages(). > - No page reference possible since no page status is kept.. > > XPmem > - Allows use of a processes memory by remote instances of Linux. > - Provides its own reverse mappings to track remote pte. > - Established refcounts on the exported pages. > - Must sleep in order to wait for remote acks of ptes that are being > cleared. > What about ib_umem_get()? -- 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