Messages in this thread | | | Date | Sat, 16 Feb 2008 02:58:03 -0800 | From | Andrew Morton <> | Subject | Re: [patch 1/6] mmu_notifier: Core code |
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On Sat, 16 Feb 2008 11:41:35 +0100 Brice Goglin <Brice.Goglin@inria.fr> 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..
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