From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 4 Feb 2008 22:11:24 -0800 (PST) From: Christoph Lameter Subject: Re: [PATCH] mmu notifiers #v5 In-Reply-To: <20080205052525.GD7441@v2.random> Message-ID: References: <20080131045750.855008281@sgi.com> <20080131171806.GN7185@v2.random> <20080131234101.GS7185@v2.random> <20080201120955.GX7185@v2.random> <20080203021704.GC7185@v2.random> <20080205052525.GD7441@v2.random> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andrea Arcangeli Cc: Robin Holt , Avi Kivity , Izik Eidus , kvm-devel@lists.sourceforge.net, Peter Zijlstra , steiner@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, daniel.blueman@quadrics.com List-ID: On Tue, 5 Feb 2008, Andrea Arcangeli wrote: > On Mon, Feb 04, 2008 at 11:09:01AM -0800, Christoph Lameter wrote: > > On Sun, 3 Feb 2008, Andrea Arcangeli wrote: > > > > > > Right but that pin requires taking a refcount which we cannot do. > > > > > > GRU can use my patch without the pin. XPMEM obviously can't use my > > > patch as my invalidate_page[s] are under the PT lock (a feature to fit > > > GRU/KVM in the simplest way), this is why an incremental patch adding > > > invalidate_range_start/end would be required to support XPMEM too. > > > > Doesnt the kernel in some situations release the page before releasing the > > pte lock? Then there will be an external pte pointing to a page that may > > now have a different use. Its really bad if that pte does allow writes. > > Sure the kernel does that most of the time, which is for example why I > had to use invalidate_page instead of invalidate_pages inside > zap_pte_range. Zero problems with that (this is also the exact reason > why I mentioned the tlb flushing code would need changes to convert > some page in pages). Zero problems only if you find having a single callout for every page acceptable. So the invalidate_range in your patch is only working sometimes. And even if it works then it has to be used on 2M range. Seems to be a bit fragile and needlessly complex. "conversion of some page in pages"? A proposal to defer the freeing of the pages until after the pte_unlock? -- 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