Re: How To?: Kernel Memory Mapped to User Space
Re: How To?: Kernel Memory Mapped to User Space
- Subject: Re: How To?: Kernel Memory Mapped to User Space
- From: Andrew Gallatin <email@hidden>
- Date: Fri, 7 Jun 2002 11:24:12 -0400 (EDT)
Shawn Erickson writes:
>
Why don't you have your API provide memory allocation and deallocation
>
functions that do the needed driver interaction for them? Clients of you
>
API would be required to use your methods and all would be well.
>
>
If they don't want to use your methods that is ok but then they must
>
deal with the issue themselves.
>
All of that is done as you say. They can choose between letting us
allocate memory for them, or they can choose to "register" (wire)
memory they've allocated themselves. For our most popular middleware
(MPI) we have a shim layer that overrides malloc and free in the
library they link with & makes sure to "deregister" (unwire) memory
before calling the real free to help prevent erorrs. (it also provides
a registration cache for platforms where pinning memory is expensive)
But there is a huge base of existing code that our users port to our
system; using the api correctly is sometimes more than they can
handle. Even though its rare, when they shoot themselves in the foot
our QA people think a crashed application with a bus error is
acceptable notification, but an uninterruptible hang is not.
Drew
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