Re: [PATCH][RFC][0/4] InfiniBand userspace verbs implementation

From: IWAMOTO Toshihiro
Date: Mon Apr 25 2005 - 21:06:56 EST

At Mon, 25 Apr 2005 16:58:03 -0700,
Roland Dreier wrote:
> 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.

Such HPC users cannot use the memory hotremoval feature, and something
needs to be implemented so that the NUMA migration can handle such
memory properly, but I see your point.

If such memory were allocated by a driver, the memory could be placed
in non-hotremovable areas to avoid the above problems.

IWAMOTO Toshihiro
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