From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sat, 16 Feb 2008 02:58:03 -0800 From: Andrew Morton Subject: Re: [patch 1/6] mmu_notifier: Core code Message-Id: <20080216025803.40d8ccbc.akpm@linux-foundation.org> In-Reply-To: <47B6BDDF.90502@inria.fr> References: <20080215064859.384203497@sgi.com> <20080215064932.371510599@sgi.com> <20080215193719.262c03a1.akpm@linux-foundation.org> <47B6BDDF.90502@inria.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Brice Goglin Cc: Christoph Lameter , Andrea Arcangeli , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Sat, 16 Feb 2008 11:41:35 +0100 Brice Goglin wrote: > Andrew Morton wrote: > > What is the status of getting infiniband to use this facility? > > > > How important is this feature to KVM? > > > > To xpmem? > > > > Which other potential clients have been identified and how important it it > > to those? > > > > As I said when Andrea posted the first patch series, I used something > very similar for non-RDMA-based HPC about 4 years ago. I haven't had > time yet to look in depth and try the latest proposed API but my feeling > is that it looks good. > "looks good" maybe. But it's in the details where I fear this will come unstuck. The likelihood that some callbacks really will want to be able to block in places where this interface doesn't permit that - either to wait for IO to complete or to wait for other threads to clear critical regions. >>From that POV it doesn't look like a sufficiently general and useful design. Looks like it was grafted onto the current VM implementation in a way which just about suits two particular clients if they try hard enough. Which is all perfectly understandable - it would be hard to rework core MM to be able to make this interface more general. But I do think it's half-baked and there is a decent risk that future (or present) code which _could_ use something like this won't be able to use this one, and will continue to futz with mlock, page-pinning, etc. Not that I know what the fix to that is.. -- 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