application needs fast access to physical memory

[steven.lin at teradyne.com]

My application needs a fast way to access a specific physical DDR memory
region. The application runs on an MPC8548 PowerPC which has an MMU. I've
tried two approaches that are typical for Linux, mmap() and using a kernel
module that implements read()/write() into this region and I'm finding that
performance is very slow for both. It's a couple orders of magnitude slower
than, for example, copying a large buffer from one place in the
application's virtual memory to another place in the application's virtual
memory.

Steve Lin
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