Date: Mon, 25 Apr 2005 17:11:45 -0700
From: Andrew Morton <akpm@osdl.org>
To: Roland Dreier <roland@topspin.com>
Cc: timur.tabi@ammasso.com, hch@infradead.org, hozer@hozed.org,
       linux-kernel@vger.kernel.org, openib-general@openib.org
Subject: Re: [PATCH][RFC][0/4] InfiniBand userspace verbs implementation
Message-Id: <20050425171145.2f0fd7f8.akpm@osdl.org>
In-Reply-To: <52vf6atnn8.fsf@topspin.com>
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Roland Dreier <roland@topspin.com> wrote:
>
>     Andrew> ug.  What stops the memory from leaking if the process
>     Andrew> exits?
> 
>     Andrew> I hope this is a privileged operation?
> 
> I don't think it has to be privileged.  In my implementation, the
> driver keeps a per-process list of registered memory regions and
> unpins/cleans up on process exit.

How does the driver detect process exit?

>     Andrew> It would be better to obtain this memory via a mmap() of
>     Andrew> some special device node, so we can perform appropriate
>     Andrew> permission checking and clean everything up on unclean
>     Andrew> application exit.
> 
> This seems to interact poorly with how applications want to use RDMA,
> ie typically through a library interface such as MPI.  People doing
> HPC don't want to recode their apps to use a new allocator, they just
> want to link to a new MPI library and have the app go fast.

Fair enough.
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